Transglutaminase Levels and Immunologic Functions of BCG-Elicited Mouse Peritoneal Macrophages Isolated by Centrifugal Elutriation

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Abstract
BCG-elicited mouse peritoneal macrophages were separated into three subpopulations by counterflow centrifugal elutriation. The three subpopulations were characterized on the basis of the level of a protein cross-linking enzyme, tissue transglutaminase. Subpopulation-3 consisted of large cells (>95% esterase positive and >90% viable) and had at least a fivefold higher transglutaminase activity (35 ± 6 nmol/hr/mg) as compared to macrophages in subpopulation-1 (6 ± 2 nmol/hr/mg) and at least a threefold higher enzyme activity as compared to subpopulation-2 (11 ± 2 nmol/hr/mg). Subpopulation-3 also showed sevenfold higher phagocytosis of IgG-coated sheep red blood cells. The three subpopulations showed no difference in their ability to kill Listeria monocytogenes as determined by [3H]-thymidine release. Subpopulations-2 and -3 caused 90% inhibition of murine adenocarcinoma (EMT-6) tumor cell growth in the presence or absence of lipopolysaccharide. Subpopulation-1 had a poor ability to inhibit EMT-6 cell growth (29 ± 12%). However, in the presence of lipopolysaccharide, this activity increased by at least threefold (92 ± 7%). The three subpopulations showed no significant difference in their cytolytic activity against murine mastocytoma (P815) target cells in the presence or absence of lipopolysaccharide. These results suggest that tissue transglutaminase may have no significant role in bactericidal, tumoricidal, or tumoristatic function of macrophages; however, it might have some role in promoting the Fc-receptor-mediated phagocytic function of the macrophages.