Effects of methyl-B12 on the in vitro immune functions of human T lymphocytes.

Studies were performed using an in vitro assay system to determine whether or not methyl-B12 could affect human T-cell function. When T cells were stimulated with phytohemagglutinin and allogeneic B cells, methyl-B12 did not enhance T-cell proliferation. In contrast, remarkable enhancing effects of methyl-B12 on the proliferative response to concanavalin A (Con A) and autologous B cells at suboptimal concentrations were observed, ranging from 0.1 to 10 micrograms/ml. Concentrations of methyl-B12 sufficient to enhance cellular proliferation were able to enhance the activity of helper T cells for immunoglobulin synthesis of B cells by pokeweed mitogen. Furthermore, the presence of methyl-B12 significantly potentiated the induction of suppressor cells in Con A-activated cultures. These results suggest that methyl-B12 could modulate lymphocyte function through augmenting regulatory T-cell activities.