T cells and the anti-trinitrophenyl antibody response to fetal calf serum and 2-mercaptoethanol.

Unprimed murine lymphocytes maintained in culture medium containing fetal calf serum (FCS) and 2-mercaptoethanol (2-ME) developed very high levels of anti-trinitrophenyl (TNP) plaque forming cells (PFC). Both FCS and 2-ME contributed to the response. The development of anti-TNP PFC during culture was accompanied by a 10-fold expansion in the number of immunoglobulin-secreting cells, indicating polyclonal stimulation. However, the number of anti-TNP PFC was disproportionately high and not accompanied by a similar increase in plaques specific for sheep red blood cells. The TNP-specific plaques were not artifacts of the plaque assay since they were 98% inhibited by specific antigen. The in vitro induction of anti-TNP PFC by FCS and 2-ME was common to a number of mouse strains, although some genetic variation occurred. Nylon-wool-separated B cells, nude mouse spleen cells, and bone marrow cells all produced high levels of anti-TNP after culture with medium containing FCS and 2-ME. The addition of T cells to B-cell cultures increased the numbers of anti-TNP PFC by 1.5- to 2.5-fold. The presence of a TNP-cross-reacting antigen in FCS probably contributed to the unexpectedly high anti-TNP response. The response to the antigen in FCS was potentiated by the enhancing activity of 2-ME.