Functions and phenotypes change in macrophages (Mø,) during tumor growth.
Although analyzing functional and phenotypic changes are important in understanding
the mechanism of tumor-induced immunosuppression, it is necessary to look
beneath the surface and expose the mechanisms behind these changes. Flow
cytometrically isolated Mac-1 +, -2+, or -3+ Mø, showed that although both normal host
and tumor-bearing host (TBH) Mac-2+ Mø, were the primary source of prostaglandin
E2, no specific TBH suppressor Mø, could be identified. To determine if normal host
and TBH Mø, respond to in vitro activating agents differently, normal host and TBH
Mø, were treated with lipopolysaccharide. Functional, phenotypic, and molecular
changes were observed in the lipopolysaccharide-treated M4J. Three- and 24-h
lipopolysaccharide treatment reduced TBH Mø,-mediated suppression, while only
24-h lipopolysaccharide treatment reduced it in normal host Mø,. Prolonged adherence,
which induces Mø, differentiation, increases the number of Mac-2+ TBH Mø,.
Tumor growth causes an increase of Mø, in the
S and G2/M phases of the cell cycle.
Lipopolysaccharide and adherence increase the number of normal host Mø, in Sand
G2/M; however, these same treatments reduce the nu mber of TBH Mø, in these same