Аннотация:The theoretical and experimental analyses of epitopes of a classical MHC molecule of class I H-2Kb responsible for incompatibility reactions after transplantation were carried out. The search of the MHC-binding motifs in the molecule primary structure along with the direct experimental data on antigenic peptides of this molecule containing such motifs have shown that reactions of indirect allogeneic recognition within the context of classical MHC molecules of a recipient contribute little to the development of allogeneic reaction. Assessment of cross-reactivity of the cell population exhibiting Kb-specific memory for mutant forms of this MHC molecule has shown that the most essential role belongs to the direct recognition of narrow structural patterns formed by the allogeneic MHC molecule associated with endogenous peptides. Practically in all mutant forms of classical MHC class I molecules revealed in the graft rejection tests, mutations give rise to amino acid sequences identical to the same fragments of some known allelic forms of the same molecules, which may be the basis of the limited structural variety of MHC molecules responsible for allogeneic reactions.