Carrier-specific B cells play a role in the production of an antigen-specific T-cell-replacing factor.

An in vitro anti-hapten response to dinitrophenylated monomeric flagellin (DNP-MON) was used to examine the ability of T cells to collaborate with B cells across a cell-impermeable Millipore membrane. It was found that T cells alone were not able to collaborate with B cells across the membrane. However, B and T cells together produced a T-cell-replacing factor that passed through the membrane and partially restored the antibody response of B cells cultured beneath the membrane. Production of the factor was abolished when carrier-specific B cells were inactivated by [125I]polymeric flagellin (POL) suicide. The T-cell-replacing factor was shown to be nondialysable and antigen-specific. It was also demonstrated that macrophages were required for production of the specific T-cell-replacing factor but that the action of the factor on B cells macrophage-independent.