Activation of macrophages by lymphokines: Enhancement of phagosome-lysosome fusion and killing of Coccidioides immitis

Previously, it was shown that arthroconidia of Coccidioides immitis appear to inhibit phagosome-lysosome fusion and survive within normal mouse peritoneal macrophages. However, when these macrophages are exposed to antigen-stimulated T lymphocytes from immune mice, activation occurs, leading to enhanced phagosome-lysosome fusion and killing of C. immitis. Results indicate that the activation of macrophages can be effected after incubation with soluble lymphocyte product(s) (lymphokines). The activation of macrophages results if the macrophages are exposed to the lymphokine before, but not after, infection. The results indicate that the lymphocyte population responsible for the elaboration of the lymphokine is phenotypically Lyt1⁺2^- and that activation of macrophages by the lymphokine can occur across H-2 histocompatibility barriers.