Abstract: The invention relates to monovalent ligands of the human CD28 receptor, which can selectively block the interaction between CD28 and B7 without activating the CD28 receptor. Said ligands can be used in particular in the production of immunosuppressant drugs, selectively blocking T lymphocyte activation phenomena involving the CD28 receptor.

Abstract: The invention relates to humanized antibodies directed against the human lymphocyte receptor CD28. When used in a monovalent form these antibodies are antagonists, i.e. capable of blocking of the CD28/B7 interaction, without activating CD28. These antibodies can be used in particular as therapeutic agents for blocking T cell activation through the CD28 receptor.

Abstract: The invention relates to monovalent ligands of the human CD28 receptor, which can selectively block the interaction between CD28 and B7 without activating the CD28 receptor. Said ligands can be used in particular in the production of immunosuppressant drugs, selectively blocking T lymphocyte activation phenomena involving the CD28 receptor.

Abstract: The invention relates to recombinant monovalent antibodies which are heterodimers of a first protein chain comprising the variable domain of the heavy chain of an antibody of interest and the CH2 and CH3 domains of an IgG immunoglobulin and a second protein chain comprising the variable domain of the light chain of said immunoglobulin of interest and the CH2 and CH3 domains of said IgG immunoglobulin. These antibodies can be used in particular as therapeutic agents in all cases where monovalent binding to a ligand such a cellular receptor is required.