Phenotypic characterization of macrophage subpopulations and localization of factor XIII in the stromal cells of carcinomas.

The infiltration of macrophages both within and at the margin of malignant neoplasms can be extensive, but their functions are not well defined. Definitions of the antigenic phenotype defined by various monoclonal antibodies may allow insight into macrophage function. Single and double immunoenzymatic labelling techniques were used to characterize sub-populations of macrophages both within and at the margin of breast carcinoma and colorectal carcinoma using a panel of antibodies. Factor XIII, previously identified in macrophage cytoplasm, was localized at the same sites. Two major groups of tumour-associated macrophages were identified; class II MHC+, CD11c+ macrophages predominated within the neoplasm, whereas CD14+ macrophages were the major population at the invasive margin. Factor XIII+ macrophages were also seen predominantly at the invasive margin. Phenotypic variation between macrophage sub-populations may reflect functional variation such that macrophages may be beneficial or detrimental for neoplastic growth. Factor XIII derived from macrophages may be important in stabilization of fibrin deposits associated with the neoplasm.