Regulatory function of Thy-1-negative cells: V. A lymphokine of B cell origin (BEF) induces in vitro high antibody response in genetically selected low responder mice.

Studies were conducted on two lines of mice genetically selected, respectively, for high (AB/H) and low (AB/L) antibody production, in order to identify the mechanism by which genes involved in the selection express their functions. It was found that B cell-derived enhancing factor (BEF), a lymphokine of B cell origin which acts on T cells by preventing the activation of suppressor cells, is effective in inducing high responses in low responder mice, whereas it is ineffective in modulating antibody production in high responder mice. As a result, no difference was found between the responses of AB/H and AB/L mice when spleen cells were stimulated in vitro in the presence of BEF. AB/H and AB/L mice do not seem to differ in their B cell functions since no difference was found in the capacity of B cells of either line to synthesize antibodies in the presence of T cell-replacing factor (TRF), or to produce endogenous BEF. These data indicate that, at least in vitro, the character of general responsiveness of these two mouse lines mainly reflects differential reactivity of T suppressor cells. Since the two lines represent, respectively, the maximal and minimal responsiveness of an outbred population of animals, it is suggested that the individual difference in antibody response is related to individual differences of T suppressor cells in responding to the immunogen.