Thymus dependence of the IgG response: role of T cells is restricted to non-specific rather than antigen-specific factors.

We have been studying the requirement for T cells in the proliferation and maturation of partially differentiated memory cells into IgG antibody secreting cells. The role of T cells in such a system can be replaced by non-antigen-specific T-cell factor(s) present in the supernatant of a 24 h mixed lymphocyte reaction (TRF) but not by antigen-specific factors released upon in vitro induction of T-helper cells with antigen. A combination of antigen-specific and non-specific factors showed no evidence of synergy between the two sets of factors and we therefore conclude that the antigen-specific factors tested play no role in the later stages of B-memory cell maturation to IgG-antibody secreting cells.