IN-VIVO CLONAL EXPANSION OF T-LYMPHOCYTES SPECIFIC FOR AN IMMUNODOMINANT N-TERMINAL MYELIN BASIC-PROTEIN EPITOPE IN HEALTHY-INDIVIDUALS

The role of myelin basic protein (MBP) T cell recognition in the induc tion of experimental allergic encephalomyelitis (EAE) has been well es tablished in mice and rats. A remarkable restriction has been observed in T cell receptor (TCR) genes utilized by encephalitogenic T cell li nes (TCLs) specific for immunodominant epitopes in these species. Path ological similarities between this animal model and multiple sclerosis (MS) has led to consider MBP as a major candidate autoantigen in this human disorder. Unlike in inbred strains of animals, the T cell respo nse to MBP in humans is quite heterogenous with regard to fine epitope specificity. The existence of V alpha and/or V beta restriction in MB P-specific T cells, from MS patients and healthy controls, is still a matter of debate. In this study we generated 77 MBP-specific TCLs from nine healthy donors and showed that peptide 7-27 is one of the most f requently recognized epitopes. 37% of all epitope-specific TCLs recogn ized this peptide and p7-27-specific TCLs were generated from seven ou t of the nine subjects studied. A high level of in vivo clonal expansi on was observed in p7-27-specific TCLs in several subjects, which howe ver is not specific of this epitope since this phenomenon was also obs erved in p85-104- and 149-162-specific TCLs.