Lymphocytes and red blood cells as carriers in the immune response of mice and guinea pigs to soluble antigen

Coupling of soluble antigen, such as RIg, to circulating lymphoid cells or red blood cells increased immunogenicity substantially. As little as 0.01 μg RIg per 10⁷ syngeneic cells elicited an antibody response in C57B1/6J strain mice equal to 1300 μg of soluble RIg. About 20 times the amount of soluble RIg induced far less a cellular immune response in guinea pigs than RIg coupled to autologous peripheral blood cells. These cells apparently play a passive role in being able to deliver bound antigen to lymphoid tissues efficiently, thus increasing the probability of interaction between host helper T cells and antigen. This conclusion is based on the following observations: (1) red blood cells, which are not immunologically responder cells, are about as efficient as lymphoid cells; (2) lymphoid cells are not effective as carriers in mice rendered deficient in antigen-specific helper T cells: (3) the antigen coupled to cells must have carrier specificity for host helper T cells.