Mice inoculated IP with L1210 murine
leukemia vaccine and subsequently with
pyran copolymer-induced macrophages (
pyran-M phi) lived for a prolonged time after live L1210 inoculation IP.
Pyran-M phi as tentatively identified by anti-AcM.1
monoclonal antibody expressed
I-Ad antigen in
tumor vaccine-primed recipient mice and contributed to maintaining
I-Ad antigen positive (I-Ad+) macrophages at high cell density in the peritoneal cavity of recipient mice. The relevance of these I-Ad+ cells to the host antitumor response was examined by experiments in which I-Ad+ cell density in the peritoneal cavity and host antitumor response behaved in a parallel fashion. Human
interferon-alpha A/D, an agent selectively inhibiting
Ia antigen expression, and
silica, a general antimacrophage agent, strongly suppressed
I-Ad antigen expression of peritoneal macrophages of
tumor vaccine-primed and
pyran-M phi-inoculated mice and, consistently with this, the antitumor response was nullified in these mice.
Tumor vaccine-primed mice inoculated with
sodium caseinate or thioglycollate-induced peritoneal cells did not survive L1210 inoculation and, in these mice, I-Ad+ peritoneal macrophages were suppressed in number as compared with those of
tumor vaccine-primed and
pyran-M phi-inoculated mice. These results warrant further study on the contribution of I-Ad+ macrophages to
pyran copolymer-induced augmentation of the antitumor response in
tumor vaccine-primed mice.