Abstract: An immunogenicity increasing carrier substance for immunogenic determinants is composed of particles derived from gram-negative cells substantially devoid or depleted of their natural immunogenic determinants, more particularly prepared by stripping the O-antigen and core region off the lipid A by chemical cleavage (acid hydrolysis). These socalled "naked bacteria" are chemically treated with a linking reagent to provide covalently bonded intermediate linking moieties while preserving the adjuvant effect of the particles. The linking moieties have functional groups. These serve for the covalent bonding of selected haptens or antigens comprising the desired immunogenic determinants against which antibodies are to be elicited in living antibody-producing cells.

Abstract: The invention provides an immuno-reactant, being either an antigen or an antibody covalently bonded to a cross-linked film, more particularly composed of cross-linked protein or peptides, enveloping a carrier body, e.g. a solid, non-porous glass bead of 6 mm diameter. The immuno-logically active parts of the immuno-reactant are present on the surface in a form in which they are available for immunosorption. If the immuno-reactant is a protein, e.g. an antibody, it can provide all or part of the film-forming material. In a particular embodiment the film carries antibodies against a second type of antibody which is captured immunosorptively to form a "double layer" carrier-bound immunosorbent, the antigen capturing sites of the second type of antibody providing the immunosorption sites of the product. The immunosorbents are used, for example, for RIA or ELISA assays.