At the 2nd Congress of Russian Immunologists, which is holding at the boundary not only two centuries, but and millennia, we had to present views, how the knowledge about major histocompatibility system has been changed (better to say has been progressed) for the brief historical period (50-60 years). 1. Having started from two, and then three component genetic HLA structure, the further studies gave image about multicomponent genetic composition of HLA, which is still not clarified up till now. At present, HLA accounts more than 10 structural units (subloci), some of which have only recently received the names. 2. The role of MHC in "cascading" of immune reactions is indeed global. Now, the view that immune reaction is developing by "cascade" type is not argued, and all the "cascade" is mediated through MHC. 3. The studies in the field of "HLA and diseases" are looking now in new light: the leitmotif of HLA C began to sound. 4. The structure of this system is indeed unique. Now discovered subunits in DRB1 locus, where each gene appeared to be in several subvariants (forms), not seldom differing only by single amino acid, pose classical genetics in difficult situation: what can be called with gene, allele, subgene, subvariant, suballele. 5. At last, the prospective is opened for HLA using in practical purposes, which earlier was not seen, namely: the transfusion of HLA typed platelets, leukocytes, lymphocytes for increasing not only therapeutic, but economical efficiency of such procedures.