Influence of various macrophage populations on Con-A induced T-cell proliferation.

The effect of different macrophage populations and supernatants derived from these macrophages on Con-A induced lymphocyte activation in macrophage depleted lymph node cells has been investigated. All macrophage populations tested were able to restore the lymphocytic response to Con A. Macrophages of different origin and differently elicited were heterogeneous with respect to the lymphocyte-activating and inhibitory activity. Bone marrow macrophages, cultured from 6 to 14 days or obtained from animals stimulated in vivo by BCG were quite inefficient in restoring the lymphocyte proliferation and showed no inhibitory activity up to the percentage per culture tested. Normal or BCG or proteose-peptone induced peritoneal macrophages were quite efficient stimulators, thioglycollate-broth elicited peritoneal macrophages were less efficient in this respect, but very efficient inhibitors. This is reflected to some degree in the supernatants derived from these macrophages which contain T-lymphocyte activating factor (TAF) and inhibitory factors, most likely low molecular weight inhibitory factors. Bone-marrow derived macrophages do not produce either factors in amounts measurable in this assay. These results demonstrate that macrophages, depending on their origin and possibly influenced by external activation signals, are heterogeneous with respect to their function in T-cell proliferation.