Abstract: A living body component in a sample derived from a living body can be rapidly and accurately measured by reacting the sample with a reagent comprising a combined product of an affinity substance and a polypeptide having at least three acid residues derived from a strong acid, separating the resulting complex by a method applying negative change such as using an anion-exchanger, and determining the amount of the analyte to be measured, on the basis of the amount of the complex or free combined product.

Abstract: The present invention concerns a method for separating at least one species of biological entities from a sample solution, by contacting the sample with a matrix of magnetic particles formed on a substrate such as a sheet a gel, etc. The particles in the matrix are coupled to entities capable of specifically binding to the species of biological entities to be separated. The separation is carried out either for detection purposes for obtaining separately each species of biological entities or for synthesis purposes. The invention further concerns matrices of magnetic particles formed on various substrates and kits for use in the method.

Abstract: A hybridoma cell line has been produced for secreting a monoclonal antibody that binds ractopamine and is effective to detect ractopamine levels of about 1 ng/mL or lower. This monoclonal antibody may be used for the detection and quantitative determination of trace amounts of ractopamine in samples, especially in animal tissue, body fluids and feed material.

Abstract: This is invention is directed to methods of identifying analytes that are differentially present between two samples. The methods involve determining retention data by desorption spectrometry for analytes in different samples using the same selectivity conditions, comparing the data, and identifying analytes that are differentially retained.

Abstract: A biological fluid collection container comprising a cup member, a lid assembly removably mounted to the cup member comprising a housing with a downwardly extending cylindrical skirt, a luer lock with a throughgoing bore extending from one side of the lid housing. A hollow tube extends from the other side of the lid housing adjacent the luer lock and is axially aligned with the throughgoing bore of the luer lock. The hollow tube is provided with a plurality of throughgoing holes leading into its lumen along its surface to provide for a sampling along various liquid level layers of the biological fluid specimen collected in the cup member so that when the biological fluid specimen is removed from the cup member a representative sampling is obtained.

Abstract: The invention involves methods for determining analytes, and reagents for use in these methods. The methods and reagents use one or both of a polyvinyl/pyrolidone with a molecular weight of at least 360,000, and a polyethylene glycol with molecular weight of at least 40,000. The assays are carried out nephelometrically, or turbidometrically. The reagents include at least one antibody which binds the analyte. The hook effect is reduced or avoided in the practice of the invention.

Abstract: The invention concerns a solid-phase determination method and equipment and an adapter for use in these. In the method a sample is allowed to react with a separating reagent bound to the outer surface of a separate solid phase body, whereafter the body is removed from the vessel and is taken to a measurement vessel, if required through one or several intermediate step vessels. At least one vessel contains a medium needed in a determination step to be performed therein when the phase body is brought into this vessel. The invention is especially suitable for use in automatic immunodetermination systems.

Abstract: Tumor cells, particularly carcinoma cells, are separated from peripheral blood by magnetic sorting. The tumor cells are magnetically labeled with antibodies directed to tissue specific antigens, preferably cytoplasmic proteins. Labeling for cytoplasmic antigens is accomplished first permeabilizing, then fixing the cells. The cells are separated on a magnetic matrix. The number of tumor cells in the enriched fraction is used to calculate the number of tumor cells present in a patient hematopoietic sample.

Abstract: A method of releasing particulates from a solid matrix is provided. The method is effected adding to the solid matrix a degrading enzyme capable of degrading the solid matrix, to thereby release the particulates from the solid matrix.

Abstract: The invention relates to a method for detecting specific target-cells in a simple and time saving way, using paramagnetic particles, antibodies recognizing the Fc portions of target-cell associating antibodies and target-cell associating antibodies directed to specific antigen determinants in the target-cell membranes. Incubation of the cell suspension with a mild detergent and/or second set of antibodies or antibody fragments, prelabeled or not with fluorescent agents, metallocolloids, radioisotopes, biotincomplexes or certain enzymes allowing visualization, with dramatically increase the specificity of the method. The method can further be used for isolation of the target-cells by magnetic field application and kit for performing the method according to the invention is described.

Abstract: A glycated hemoglobin assay utilizes a simple procedure for the determination of standardized %GHb in whole blood samples correlated to the Diabetes Control and Complications Trial (DCCT). First, a lysed whole blood sample is incubated with a solid phase that is coupled with boronic acid or similar boronate compound through covalent linkage chemistries known in the art. Next, a labeled antibody to human hemoglobin is added and the resulting signal is directly proportional to the %GHb in the sample. The advantages of measuring %GHb using a single determination include high precision and, since the assay is easily automatable, high throughput. With automation, this assay can also be consolidated with other testing on one analyzer. The method according to the various embodiments of the invention thus eliminates the need for two measurements: one for GHb and another for total hemoglobin (THb).

Abstract: There is provided a method and kit for measuring the amount of an objective constituent contained in a specific lipoprotein in a biological sample such as serum and plasma, specifically for measuring the amount of cholesterol contained in high density lipoprotein, which can be applicable to clinical tests.

Abstract: A method for combining magnetic and centrifugal extraction techniques in a manner that improves wash efficiency and reduces the relative disadvantages of stand alone magnetic or centrifugal systems is provided. Centrifugation occurs about the rotational axis of a generally circular container with generally vertical sides featuring an inward protruding physical feature designed to retain material that exceeds the density of supernatent liquid and that is bound to magnetic particles during the centrifugation. During centrifugation, an external magnetic field is applied about the rotational axis of the container such that magnetic lines of force penetrate the container in any desired location. The magnetic and centrifugal forces may be independently modulated or modulated in relative unison to suit the hydrodynamic characteristics of a given complex.

Abstract: An affinity chromatographic matrix for purification of a biological material is provided having an ionically charged polymeric ligand such as glycoaminoglycan non-covalently bound directly by an ionic bond to an oppositely ionically charged group on a chromatographic matrix. Having the ligand non-covalently bound to the matrix by an ionic bond, allows the ligand to be easily washed off the matrix and replaced for subsequent purifications without having to replace the matrix. A biological material in a crude mixture is purified by non-covalently binding the material to the bound ligand and dissociating the material from the ligand. Matrices that may be used include crosslinked agarose, crosslinked dextran, crosslinked cellulose, crosslinked dextran and bisacrylamide, or matrices based on silica or plastic polymers. The charged group may be a quaternary amine or diethylaminoethyl group.

Abstract: A process for magnetic immunoseparation of cells, in particular bacteria, fetal cells, stock cells of bone marrow and circulating cancerous cells, of the type consisting in affixing the target cells on paramagnetic balls and in causing a magnetic field to act on a sample containing the affixed cells, the free cells and the surplus paramagnetic balls, in order to isolate the paramagnetic balls, in that the sample is caused to circulate in a tube the section of which is much less than the length over which the magnetic field is applied.

Abstract: Devices, processes and compositions are provided for effective separation of cells from a mixture of cells, where depletion or positive selection may be employed to provide a cellular population of interest. Of particular utility is the separation of cells from peripheral blood mononuclear cells, where members of the lymphoid or myeloid lineages may be isolated and used for research, diagnosis or therapy. Also of interest are cellular separation from bone marrow, tumor suspensions or lymphoid tissue suspensions, where cells can be isolated and used for a variety of purposes. The separated cells may be homogeneous, free of exogenous biologicals, viable, capable of replication and exhibit their full complement of biological activities. Multiple phenotypes can be captured simultaneously. Captured cells can be specifically activated with cytokines and antigens to provide cells which are MHC restricted and have antigen-specific effector functions.

Abstract: Novel magnetic assay methods and systems, as well as systems for conducting spectrophotometric analysis therewith. According to a preferred embodiment, the magnetic assay methods and systems incorporate a chromatographic medium, such as an assay test strip, that is designed to be contacted with a test solution having activated magnetic particles. A magnetic field, generated by a magnet or electromagnet, is additionally provided that if selectively applied to a chromatographic medium which causes the charged particles to become substantially bound at a site all in the chromatographic medium specified by the position of the magnets, to thus form a captured line or zone. To the degree of magnetic force applied to the medium may be selectively adjusted to vary the width or surface area of the capture line or zone. Additionally, in a preferred embodiment, capture lines may be formed while test strips are in motion along a stationary magnetized rail.

Abstract: The superparamagnetic monodispersed particles comprise a core of a first polymer, an internal layer of a second polymer coating the core and in which a magnetic material is distributed, and an external layer of a third polymer coating the magnetic layer and capable of interacting with at least one biological molecule. At least the second polymer is heat sensitive and has a predetermined lower critical solubility temperature (LCST) of 15-65.degree. C. These particles may be used to isolate at least one biological molecule from a liquid specimen.

Abstract: Provided is a magnetic separation device comprising a container having one or more outer surfaces; at least one magnetic sheet; and a physical coupler that is used to detachably secure the container to the magnetic sheet.

Abstract: The invention provides methods for separating bound label from unbound label within an assay mixture, for predispensing assay reactants in self-contained assay vessels, as well as for detecting the presence and/or amount of an analyte within a fluid sample. In addition, a reusable detection vessel for use therein and with specific binding assays in general is disclosed. In the methods, generally an analyte within a sample is detected or measured by forming an assay mixture containing sample, analyte binding components and label, placing the assay mixture in contact with an immisable primary layer, subjecting the assay mixture to conditions that separate the analyte bound with binding components and label from unbound binding components and label, and subsequently detecting bound label.

Abstract: A suspension of inert particles is prepared in an aqueous solution, to which an antibody or an antigen and a carrier-bound antigen or antibody, respectively, are added in any desired order. After centrifuging, the positive, weakly positive, or negative reaction can easily be recognized on the basis of a simple pattern.

Abstract: Provided is a magnetic separation device comprising a container having one or more outer surfaces; at least one flexible magnetic sheet; and a non-permanent adhesive that is used to detachably secure an outer surface of the container to a flexible magnetic sheet.

Abstract: The present invention concerns methods for masking inhomogeneity of a member of a specific binding pair (sbp) employed in a capillary electroseparation. The method comprises binding the sbp member to synthetic particles that become localized during capillary electroseparation. Also disclosed is one embodiment of the present invention, which is a method for conducting a capillary electroseparation specific binding assay. The method involves the electroseparation of a labeled first member of a specific binding pair that is bound in a complex from labeled first member that is not bound in the complex. The complex comprises the first member and a second member of a specific binding pair. A combination is provided comprising a sample suspected of containing an analyte, a labeled first member of a specific binding pair, and a second member of a specific binding pair under conditions for forming a complex between labeled first member and the second member.

Abstract: A dual particle immunoassay method and kit for detecting analyte in a sample in which the sample to be analyzed, a binding molecule specific for the analyte, and a particle coated with the analyte to be detected or coated with a second binding molecule are reacted and applied to a porous membrane. The competitive immunoassay utilizes an analyte-coated particle, whereas the sandwich immunoassay employs a second binding molecule-coated particle. All of the reagents except for the coated particle are able to pass through the porous membrane. Detectable particles coated with a binding substance that binds to the binding molecule, such as protein A protein G, second antibody reactive to the binding molecule, or a small synthetic affinity ligand, are reacted with coated particles retained on the membrane surface. The detectable particles will pass through the membrane if not complexed with the coated particle.

Abstract: A method of detecting an antibody in a sample using a labelling compound and comprising the steps of mixing a ligand antigen, antibody or hapten bound to biotin with the sample; an antibody directed against the antibody to be detected bound to paramagnetic particles; and a chemiluminescent acridinium compound bound to avidin or streptavidin to form a solid phase complex; separating the solid phase from the liquid phase; and analyzing the separated solid phase for the presence of chemiluminescent complex.

Abstract: An ultrasonic energy source is used to provide a variable force for measuring the binding forces between molecular entities and for sensing the presence of an analyte in a test sample. The device includes a surface that has a first binding member attached thereto and one or more particles that have a second binding member attached thereto. A reaction vessel is provided for exposing the surface to the particles whereby, if the first binding member has a binding affinity for the second binding member, a complex is formed between individual first binding members and individual second binding members and the particles thereby become immobilized with respect to the surface. The ultrasonic energy source is positioned for applying a variable ultrasonic force onto the surface, and the position of the particles is monitored as the intensity of the ultrasonic force is varied.

Abstract: A novel signal amplification system for immunoassays that minimizes non-specific signals is disclosed. Immunoassay methods, reagents and test kits are described for obtaining immunoassays of enhanced sensitivity. The reagents include antibody-variant DNA conjugates, wherein the variant DNA is a substrate for an RNA-dependent RNA polymerase, such as, QB replicase. Immunoassay methods to detect, or to detect and quantitate, analyte in test samples comprise transcribing the variant DNA of said antibody-DNA conjugates that are bound to analyte, to RNA, and replicating the RNA transcripts, wherein the presence or quantity of variant RNA replication products can be correlated with the presence or quantity of analyte in the test samples. Further, methods are provided to detect, or to detect and quantitate, simultaneously two or more analytes in a test sample.

Abstract: This disclosure relates to novel antibodies specific to the recently discovered receptor to human interleukin 12 (IL-12R). The antibodies to IL-12R, most preferably, the monoclonal antibodies to that protein, are useful in determining the status of the human immune system and as diagnostic reagents or potential therapeutic reagents for conditions involving imbalances in IL-12 levels or cell types sensitive to IL-12 activation.Further aspects of the disclosure relate to methods of producing and purifying such novel antibodies and hybridoma cell lines capable of their production. Another aspect of the disclosure relates to an immunoprecipitation assay for the detection of solubilized IL-12R which employs, in a preferred embodiment, monoclonal antibodies to the receptor of the present invention covalently bound to Protein G-Sepharose resin.

Abstract: Improvements in the existing procedures and materials for conduct of high gradient magnetic separation (HGMS) are disclosed. The use of plastic coated matrices especially small spheres or balls which form superior magnetic gradient-intensifying supports are disclosed, along with improved methods and apparatus to conduct HGMS. The selection of small spheres in combination with the coating provides for uniform matrices of high stability.

Abstract: A method for identifying a toxicant in an environmental water or soil sample comprising (a) adding to the sample an antibody known to form a complex with a toxicant suspected to be present in the sample; (b) incubating the antibody with the sample for a time and under conditions sufficient to allow complexes to form between the antibody and the toxicant; and (c) comparing the toxicity of the sample treated as in the step (b) with the toxicity of the sample prior to the step (a), whereby a reduced amount of toxicity of the treated sample compared with the untreated sample indicates the presence of the toxicant in said sample. The method described herein provides unexpected and important advantages by providing more accurate correlations between predicted and observed toxicity of a sample than previous methods.

Abstract: A method is provided, in one embodiment, for the determination of an analyte in a biological fluid sample in the presence of a substance interfering with an assay for the analyte. This embodiment is implemented by using antibodies to cause the selective immunoreaction of at least one of the analyte or the interfering substance and then conducting an assay for the analyte in at least one of the immunoreactants or the non-reactants. Another embodiment provides a disposable reaction device to implement the method. The invention is applicable to the detection of a wide variety of analytes, including cholesterol in a targeted lipoprotein class in the presence of cholesterol in another class; to targeted isozymes of enzymes such as creatine kinase, lactate dehydrogenase, amylase, and alkaline or acid phosphatases in the presence of other isozymes; as well as to targeted immunoglobulins in the presence of non-targeted immunoglobulins.

Abstract: Dendritic cells (DCs) are the primary antigen presenting cells during the initiation of T cell-dependent immune responses. The cells originate from the bone marrow and have been suggested to represent a distinct cell lineage. However, distinct DC precursors have not been identified in bone marrow, and mature monocytes can also give rise to DCs. The instant invention presents a distinct DC precursor among bone marrow CD34+ cells. The cells express high levels of the interleukin-3 receptor a chain and CD4 and can be uniquely identified also in blood and lymphoid tissues by this phenotype.

Abstract: Magnetic particles are used as the solid phase to carry out immunoassay. In a reaction vessel, the magnetic particles are mixed with a sample containing TSH as an analyte and a labeled antibody. A chemiluminescent label material is bound onto the magnetic particles with an immunoreaction. A fluid including the above mixture is introduced to a chamber inside a flow through cell, the chamber being sized to have a width greater than a depth. The magnetic particles in the fluid are trapped by a magnet so as to be spread in the planar form over a predetermined area within the chamber, while useless materials are discharged outwardly of the chamber. The chamber is then filled with a buffer solution containing an attractant. By applying a voltage to electrodes disposed in the chamber, the label material on the magnetic particles is excited to emit an electro-chemiluminescence. The luminescence is detected by a photomultiplier.

Abstract: The present invention relates to novel methods and devices for detecting non-complexed prostate specific antigen (free PSA), which is used in conjunction with total PSA tests to identify patients having either benign prostatic diseases (BPD), such as benign prostatic hyperplasia, prostatitis, or glandular atrophy or prostatic adenocarcinoma (CAP). In a biological sample, one can find not only free PSA, but also prsotate specific antigen (PSA) which has formed a complex with .alpha.1-antichymotrypsin (ACT). The present invention removes complexed PSA (PSA-ACT) from a fluid sample, thereby removing any possible interference due to binding of complexed PSA to an allegedly free PSA specific antibody in an immunoassay for free PSA.

Abstract: An apparatus and method for immunomagnetic separation and concentration of target biological materials is disclosed. The immunomagnetic separation is performed by a magnetic flow cell, or filter block, as part of an automated mostly continuous immunomagnetic assay system. The magnetic flow cell has two bundles of ferromagnetic rods or pins positioned inside an internal chamber so that a fluid sample flowing through the flow cell passes through the pins. A pair of cobalt magnets flank the flow cell so that the pins concentrate and sufficiently increase the magnetic fields so that even nanometer size magnetic beads can be captured. The overall system combines a reaction subsystem for reacting coated magnetic beads with a sample, a collection subsystem for capturing magnetic beads, a rinsing subsystem for removing debris and a filtering subsystem for removing captured magnetic beads from the collection subsystem. The new magnetic flow filter is the key component for the collection and filtering subsystems.

Abstract: Disclosed is apparatus for detecting the presence of an analyte of interest in a sample, comprising an immobilised binding partner comprising a solid support and a reversibly binding receptor which is capable of binding to the analyte of interest thereby causing a measurable change in a property of the immobilised partner, and detection means for detecting the measurable change and a method for detecting the presence of an analyte of interest.

Abstract: Apparatus and method for detection of low levels of about 1 ppb of analyte in samples using an enclosed permeable membrane enrichment device and agglutination reaction slide test apparatus.

Abstract: A method of assessing glycated blood protein in a sample which comprises separating glycated and non-glycated protein using a liquid phase precipitation reagent, contacting the sample with a signal forming agent capable of binding preferentially to the glycated protein, and assessing the signal forming agents.

Abstract: Antivenoms to snake, spider, scorpion and jelly fish venoms are produced for treatment of humans and animals, and for analytical use. Polyvalent antivenoms are produced containing immunoglobulin which is greater than fifty percent venom reactive. Purified polyvalent antivenom is derived from a first polyvalent antivenom having two or more monovalent subpopulations, and purified such that greater than fifty percent of the monovalent subpopulations are recovered by weight. The antivenoms can be horse or avian such as chicken antivenom. Chicken antivenom is obtained using a whole venom that is not glutaraldehyde pretreated, and the antivenom contains yolk immunoglobulin. Antivenoms are purified with an antigen matrix containing a single whole venom or a plurality of whole venoms covalently attached to an insoluble support such as aldehyde-activated agarose. Preferably, the whole venoms forming the plurality of whole venoms are selected from the four whole venoms of C. atrox, B. atrox, C. adamanteus and C.

Abstract: The present invention is a method useful for the detection of bloodgroup antigens and antibodies. The method of the present invention is envisioned for two types of assays: a direct assay and an indirect assay. The direct assay comprises adding a sample of erythrocytes to a reaction tube charged with two layers of immunoreactive particles, a first layer, preferably Sepharose, having Protein G coupled to the surface of those particles and a second layer, preferably Sephacryl S-200, having Protein A coupled to those particles in a buffer solution. Antibodies specific for the bloodgroup antigens tested for are coupled to the Protein G. The reaction tube is then centrifuged for a time sufficient to force to the bottom of the reaction tube erythrocytes that do not attach to the antibodies.

Abstract: An immunoassay plate for an immune complex transfer immunoassay, comprising a well type solid phase and a dip stick type solid phase which can be inserted into said well type solid phase, wherein the dip stick type solid phase is coated with either substance (A) or (B) to be mentioned below and the well type solid phase is coated with the other, remaining substance, and these solid phases are used as the two solid phases to be used for an immune complex transfer immunoassay:(A): a substance having a reactive group which specifically binds to a functional group previously introduced onto a substance, which specifically forms an immune complex with a test substance(B): a substance having a reactive group capable of specifically binding to the test substance in the immune complex, a substance which specifically forms an immune complex with the test substance, or a functional group conjugated in advance with said substance, provided that the moiety which binds to the reactive group of (A) does not bind to the rea

Abstract: A method is provided for differentiating leukocyte subpopulations, immunophenotyping of lymphocytes and counting white blood cells. The method preserves leukocyte morphology and surface markers without using fixatives. In addition, the method finds utility in determination of hemoglobin concentration without using cyanide. The stable hemoglobin chromogen formed is measured at approximately 540 nm.

Abstract: A device and method is disclosed for the identification, concentration and isolation of a chemical compound from a mixture of compounds on the basis of the binding affinity of the chemical compound to a macromolecule or complex thereof, that is, to a receptor. Both the compounds to be assayed, and the macromolecules to which the compounds may bind, are free in solution. The method comprises contacting a mixture of compounds in solution with a solution of macromolecules or complexes thereof in a device possessing an ultrafiltration membrane to retain the receptor and bound compound receptor complex; washing through the device non-bound compounds; and releasing a bolus of the bound compound which passes through the ultrafiltration membrane where it may be analyzed chemically and/or spectrally (e.g. mass spectrometry) and/or bioassayed. The device includes a barrier such as an ultrafiltration membrane separating a binding chamber and an effluent chamber.

Abstract: The invention concerns interference-eliminating agents for avoiding unspecific interactions in immunoassays in which avidin or streptavidin or a derivative thereof are used as the interference-eliminating agents.

Abstract: A suspension of inert particles is prepared in an aqueous solution, to which an antibody or an antigen and a carrier-bound antigen or antibody, respectively, are needed in any desired order. After centrifuging, the positive, weakly positive, or negative reaction can easily be recognized on the basis of a simple pattern.

Abstract: The present invention relates to methods of enriching for desired cell population from cell sources, such as body fluids, dispersed tissue specimens and cultured cells. In particular, the present invention relates to the use of a cell-trap centrifugation tube containing a specific density gradient solution adjusted to the specific density of a desired cell population to enrich for the desired cell from a cell source. The tube allows the desired cell population to be collected by decantation after centrifugation to minimize cell loss and maximize efficiency. In addition, the method can be further simplified by density-adjusted cell sorting which uses cell type-specific binding agents such as antibodies and lectins linked to carrier particles to impart a different density to the undesired populations in a more convenient manner. The rapid cell enrichment method described herein has a wide range of diagnostic and therapeutic applications.

Abstract: Disclosed are novel protein and peptide compositions comprising soluble and bound forms of immunologically-active blood group antigens including mammalian Rh antigens. In preferred embodiments methods for the isolation and purification of serologically-active human Rh antigens such as D, c, C, E, and e are disclosed. Also disclosed are methods for the adsorption of immunologically-active Rh antigens to solid supports. Diagnostic kits, methods, and devices for the detection of Rh antibodies in clinical and non-clinical samples are also disclosed. Devices, compositions and methods for the isolation, purification and quantitation of anti-Rh antibodies from solution are also provided.

Abstract: A species such as a microorganism, e.g. Legionella, Giardia or Cryptosporidium, is captured by first attracting plastic coated magneticbeads or other magnetically attractable particles to a solid support such as stainless steel mesh, which particles have a selective affinity for the species, e.g. by virtue of an antibody coating, and contacting a sample containing the species with the particles on the solid support. The beads bearing the captured species may be released by reduction of the magnetic attraction of the support for the beads, e.g. by turning off an electromagnet used to magnetize the support.

Abstract: The present invention relates to a novel clinical examination method which comprises analyzing the alteration in the amount of a specific component in oligosaccharides of immunogloblin G. Human diseases such as liver diseases, malignant hypertension, immunogloblin A-nephropathy, pediatric disorders, etc., are examined in terms of the alteration in bisecting N-acetylglucosamine-containing oligosaccharides in immunogloblin G from collected humor. The present invention provides highly accurate information in a manner applicable to practical operation for examination of liver diseases, allergic diseases, malignant hypertension, immunogloblin A nephropathy, pediatric disorders, as well as aging-dependent variations and the therapeutic effect of interferon.

Abstract: Disclosed is a method of isolating a ligand from a sample, the method including: providing a hybrid molecule including the receptor for the ligand covalently bonded to the first member of a specific binding pair; contacting sample with the hybrid molecule to form an affinity complex between the ligand and the hybrid molecule; and isolating the affinity complex using the second member of the specific binding pair. Also disclosed is a c-kit ligand, nucleic acid encoding such a ligand, and recombinant cells containing such nucleic acid. The c-kit ligand may be used to stimulate hematopoietic cell growth.