T cell suppression of contact sensitivity in the mouse. III. The role of macrophages and the specific triggering of nonspecific suppression

Passive transfer of contact sensitivity and suppression of contact sensitivity by lymph node cells is abolished by treatment with anti‐Θ serum and complement. In contrast, both these forms of passive transfer by peritoneal exudate cells resist treatment with anti‐Θ serum but are abolished by trypsin. This suggests that the cell responsible in the peritoneal exudate is a macrophage or other Θ‐negative cell. Peritoneal exudate cells can be armed for suppression by incubation in suppressor supernatant and a similar cell is probably responsible. Double transfer experiments show that suppressor lymph node cells produce factor(s) in vivo which inhibit “macrophage‐mediated transfers” of skin reactions. The specificity of the passive transfer of suppression by suppressor lymph node cells, suppressor peritoneal exudate cells, and peritoneal exudate cells armed for suppression was studied. All systems were specific in that the cells failed to suppress passive transfer of contact sensitivity to 4‐ethoxy‐methylene‐2‐phenyloxazolone (Ox) when the recipients were challenged with Ox. However, in the peritoneal exudate cell systems but not in the lymph node system, nonspecific suppression occurred when mice were challenged with a mixture of two antigens – picryl chloride corresponding to the suppressor cells, and Ox corresponding to the cells mediating passive transfer. The hypothesis is put forward that lymphocytes convey a factor to macrophages which enables them, in the presence of antigen, to suppress the passive transfer of contact sensitivity nonspecifically.