The isoantigen is based on a special protein that is present in the blood and lymph of almost all vertebrates - up to 20 thousand species. This protein forms antigenically unique structures, which are called isotypes, by analogy with those described in humans. The Mnss system includes about 140 isotypes, of which groups A and C are the most significant for our body. Over 23 thousand mutant genes belonging to the Mnss system have been identified. It has been shown that only one of them - the type I gene of the system - is located in the nucleus of human liver cells, the remaining genomes are located in the cytoplasm of cells, but are actively involved in the control of genomic repression and regulation of DNA transcription processes. To date, more than 30 genes have also been discovered that regulate the level of β-globin of some isotypes. It is known that, unlike people of other nationalities, in Russia the group of the Mnss Aα1 system predominates at the entire post-bifid level of lymphocyte heterotopia. According to the results of a study by H. Cheng et al. (201