Abstract: A ligand regulated protein-protein interaction system based on a lipocalin-fold molecule including: (a) a lipocalin-fold molecule; (b) a lipocalin-fold ligand with a low molecular weight of 1500 Da or below; and (c) a lipocalin-fold binding interaction partner, wherein the lipocalin-fold molecule can bind to the lipocalin-fold ligand; and wherein the lipocalin-fold molecule bound to the lipocalin-fold ligand binds to the lipocalin-fold binding interaction partner with an affinity which is at least 10-fold higher than the affinity of the lipocalin-fold molecule not bound to the lipocalin-fold ligand; and wherein the lipocalin-fold binding interaction partner is not a naturally occurring protein which has an affinity of <10 ?M to any naturally occurring lipocalin-fold molecule in the presence of any lipocalin-fold ligand.

Abstract: A ligand regulated protein-protein interaction system based on a lipocalin-fold molecule including: (a) a lipocalin-fold molecule; (b) a lipocalin-fold ligand with a low molecular weight of 1500 Da or below; and (c) a lipocalin-fold binding interaction partner; wherein the lipocalin-fold molecule can bind to the lipocalin-fold ligand; and wherein the lipocalin-fold molecule bound to the lipocalin-fold ligand binds to the lipocalin-fold binding interaction partner with an affinity which is at least 10-fold higher than the affinity of the lipocalin-fold molecule not bound to the lipocalin-fold ligand; and wherein the lipocalin-fold binding interaction partner is not a naturally occurring protein which has an affinity of <10 ?M to any naturally occurring lipocalin-fold molecule in the presence of any lipocalin-fold ligand.

Abstract: An extracellular domain of CD19 (CD19-ECD) which comprises at least 90% sequence identity to SEQ ID NO:1, a first core region at positions 2-98 of SEQ ID NO:1, a second core region at positions 167-258 of SEQ ID NO:1, a third core region at positions 99-166 of SEQ ID NO:1, and at least one stabilizing point mutation at an amino acid position within said first and/or second and/or third core regions, wherein the CD19-ECD has an increased thermal stability compared to CD19-ECD which consists of an amino acid sequence identified as SEQ ID NO:1.

Abstract: Disclosed is a group of chimeric antigen receptors (CARs) having two, three or four CAR molecules, wherein each member of the group of CARs is different in its amino acid sequence from one another, and wherein each of the CAR molecules of the group include at least a transmembrane domain and an ectodomain, wherein the ectodomain has one or two antigen binding moieties and/or one or two binding sites to which other polypeptides each including at least an antigen binding moiety are able to bind; wherein the ectodomain of each CAR molecule of the group in its prevalent conformation is free of cysteine amino acid moieties which are able to form intermolecular disulphide bonds with other CAR molecules of the group, respectively, and wherein each CAR molecule of the group includes at least one heterodimerization domain.

Abstract: A group of chimeric antigen receptors (CARs) having two, three or four CAR molecules, wherein the members of the group of CARs can be different in their amino acid sequences, and wherein each of the CAR molecules of the group includes at least a transmembrane domain and an ectodomain comprising either an antigen binding moiety or a binding site to which another polypeptide is able to bind, wherein the polypeptide comprises an antigen binding moiety; wherein each CAR molecule of the group includes at least one dimerization domain, wherein this dimerization of a pair of dimerization domains is either induced by a regulating molecule and optionally reduced by another regulating molecule, or occurs in the absence of a regulating molecule and is reduced by a regulating molecule, and wherein the antigen binding moieties of the CAR molecules of the group specific for one target antigen.

Abstract: A ligand regulated protein-protein interaction system based on a lipocalin-fold molecule including: (a) a lipocalin-fold molecule; (b) a lipocalin-fold ligand with a low molecular weight of 1500 Da or below; and (c) a lipocalin-fold binding interaction partner; wherein the lipocalin-fold molecule can bind to the lipocalin-fold ligand; and wherein the lipocalin-fold molecule bound to the lipocalin-fold ligand binds to the lipocalin-fold binding interaction partner with an affinity which is at least 10-fold higher than the affinity of the lipocalin-fold molecule not bound to the lipocalin-fold ligand; and wherein the lipocalin-fold binding interaction partner is not a naturally occurring protein which has an affinity of <10 ?M to any naturally occurring lipocalin-fold molecule in the presence of any lipocalin-fold ligand.