[Abnormalities in autologous mixed lymphocyte reaction-induced T cell activation cascade in rheumatoid arthritis and their possible correction by methyl-B12].

We have previously shown that when patients with active rheumatoid arthritis (RA) were examined for the ability of their lymphocytes to respond in the autologous mixed lymphocyte reaction (AMLR), profoundly reduced AMLR responses were found in the RA patients. The defects were mainly due to the impaired response of CD8+ and CD4+ Law8- subsets; however, both CD4+Leu8+ and CD4+ + Leu8- cells functioned normally as responding cells. The present study demonstrated that the abnormalities of RA CD8+ T cells in the AMLR were corrected when the AMLR cultures were set up in the presence of methyl-B12. In addition, a main target of the methyl-B12 effect observed was both CD8+Leu8+ and CD8+Leu8- cells. Thus, methyl-B12 may become a potential agent that would be able to control the pathophysiology of RA.