Two-color flow cytometric analysis of the expression of MAC and MHC Class II antigens on macrophages during tumor growth

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Abstract
Tumor-bearing host (TBH) macrophages (Mϕ) exhibit immune dysfunction that is concomitant with phenotypic changes. We examined Mϕ subpopulations by changes in the expression of surface antigens Mac-1, -2, -3, and Ia on normal and TBH peritoneal and splenic Mϕ. Mϕ were double-labeled and analyzed by flow cytometry to observe multiple expression of surface antigens. Tumor growth alters the multiple expression of these Mϕ markers. Peritoneal and splenic Mϕ had different Mac+ and Mac+ Ia+ population percentages. In TBH, peritoneal Mϕ had decreased percentages of Mac-1+2+, Mac-1+3+, Mac-2+3+, and Mac+Ia+ Mϕ. This decrease correlated with functional changes in TBH Mϕ. In contrast, there was an increase in Mac-2−Ia− TBH peritoneal Mϕ. Previously undiscovered Mac-1+2−3− and Mac-1−2−3+ populations were found. In contrast to peritoneal Mϕ, there was an increase in the percentage of Mac-1+2+, Mac-1+3+, and Mac-2+3+ splenic TBH Mϕ but, like peritoneal Mϕ, there was a decrease in the percentage of Mac+Ia+ Mϕ. Also, TBH splenic Mϕ showed a smaller but more uniform antigen density than normal host splenic Mϕ. Tumor growth modulated phenotypic alterations in peritoneal and splenic Mϕ subpopulations. Combined with earlier functional studies of Mϕ subpopulations, these data suggested a relationship between changes in Mϕ phenotype and tumor-induced dysfunction of Mϕ-modulated immune activity.