CONTRIBUTION OF THYMus-DERIVED CELLS AND ANTIBODY-FORMING CELL PRECURSORS TO IMMUNOLOGICAL MEMORY*, BY

Interaction between thymus-derived (T) 1 and nonthymus-derived (B) cells occurs in the primary humoral antibody response of mice to heterologous erythrocytes (1-3) and serum proteins (4, 5). Unequivocal evidence has shown that the B cells are the antibody-forming cell precursors (AFCP) (6-8) and that immunological specificity characterizes both T and B cells before intentional antigenic stimulation (9). Although it is known that the faculty of immunological memory is carried by small lymphocytes (10), the relationship between memory and T and B cells is not clear. Answers to the following questions must be sought: Is collaboration between T and B cells obligatory for the generation of memory cells (in thymus-dependent humoral antibody responses)? Do both T and B cells carry memory and, if so, is the memory directed towards the same or different antigenic determinants? Is collaboration between T and B cells essential to activate memory cells in secondary antibody responses or does priming entail a qualitative change in B cells which permits them to interact directly with antigen without the need for the participation of T cells? Cell transfer experiments to date have led to different conclusions; in one case it appeared that T cells carried memory (11) whereas in another it seemed that memory was a function carried exclusively by B cells (12). In the secondary anti-hapten antibody response to hapten-protein conjugates, the data supports the concept that T cells are involved (13) and react to separate determinants on the carrier protein whereas B cells are responsible for producing antibody to the haptenic determinant (5, 14, 15).