Macrophage cell lines P388D1 and IC-21 stimulated with gamma interferon fail to inhibit the intracellular growth of Histoplasma capsulatum.

Histoplasma capsulatum, a facultative intracellular parasite of macrophages, grows within mononuclear cells of the P388D1 and IC-21 cell lines with a generation time comparable to that with which it grows in normal resident peritoneal macrophages (10 +/- 2 h). Recombinant murine gamma interferon (rMuIFN-gamma) activates P388D1 cells to express la antigens but not to inhibit the intracellular growth of H. capsulatum, alone or in combination with lipopolysaccharide. IC-21 cells also could not be activated to fungistasis with rMuIFN-gamma. Explanted resident peritoneal macrophages of the C57BL/6 (from which the IC-21 cell line derives), C3H/HeJ, DBA/2 (from which the P388D1 cell line derives), A/J, and SJL/J strains of mice were all stimulated by rMuIFN-gamma to inhibit the fungus.