Murine T cell proliferation can be specifically augmented by macrophages fed with specific antigen:...

Foreign antigens conjugated to alpha-2-Macroglobulin (alpha-2-M) were effectively taken up by murine macrophages via alpha-2-M receptors. Such effective internalization of alpha-2-M:antigen conjugate by macrophages resulted in a remarkable increase in its ability to activate murine immune T cells under the following conditions. After macrophages were incubated with alpha-2-M:antigen conjugate or unconjugated antigen, they were cultured with immune T cells and antigen-stimulated tritiated thymidine incorporation by T cells was measured. The stimulation of T cell proliferative response by macrophages fed with the conjugate was sixteen times higher than what was observed with macrophages pretreated in the same concentration of unconjugated antigen. These findings suggest a physiological function of alpha-2-M and give us a new technique of immunization.