Cell-to-cell interaction in the immune response. VI. Contribution of thymus-derived cells and antibody-forming cell precursors to immunological memory.

Collaboration between thymus-derived lymphocytes and nonthymus-derived antibody-forming cell precursors occurs in the primary antibody response of mice to heterologous erythrocytes and serum proteins. The purpose of the experiments reported here was to determine whether collaboration took place in an adoptive secondary antibody response. A chimeric population of lymphocytes was produced by reconstituting neonatally thymectomized CBA mice soon after birth with (CBA x C57BL)F(1) thymus lymphocytes. These mice could be effectively primed to fowl immunoglobulin G (FgammaG) and their thoracic duct lymphocytes adoptively transferred memory responses to irradiated mice. The activity of these cells was impaired markedly by preincubation with CBA anti-C57BL serum and to a lesser extent by anti-theta-serum. Reversal of this deficiency was obtained by adding T cells in the form of thoracic duct cells from normal CBA mice. Cells from FgammaG-primed mice were at least 10 times as effective as cells from normal mice or from CBA mice primed to horse erythrocytes. These results were considered to support the concept that memory resides in the T cell population and that collaboration between T and B cells is necessary for an optimal secondary antibody response. Poor antibody responses were obtained in irradiated mice given mixtures of thoracic duct cells from primed mice and of B cells from unprimed mice (in the form of spleen or thoracic duct cells from thymectomized donors). In contrast to the situation with T cells, the deficiency in the B cell population could not be reversed by adding B cells from unprimed mice. It was considered that memory resides in B cells as well as in T cells and that priming probably entails a change in the B cell population which is fundamentally different from that produced in the T cell population.