HETEROGENEITY OF IMMUNOLOGICAL FUNCTION AMONG SUBFRACTIONS OF NORMAL RAT ALVEOLAR MACROPHAGES .2. ACTIVATION AS A DETERMINANT OF FUNCTIONAL-ACTIVITY

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Abstract
Differences in immunologic function among density-fractionated alveolar macrophages were previously demonstrated. These functional differences among alveolar macrophage density fractions were correlated with parameters of macrophage activation. Alveolar macrophages were lavaged from normal rats and separated into 5 density fractions by density gradient centrifugation. Cells from each density fraction were analyzed for parameters of macrophage activation: in vitro cytotoxic function directed against cultured neoplastic cells, ectoenzyme activities and surface expression of Ia-like determinants. Lavaged alveolar macrophages with in vitro cytotoxic function were concentrated among cells from higher density fractions and cytotoxic function among the density fractions correlated inversely with ectoenzyme activities. Although the percentage of la-positive cells varied among the density fractions, surface expression of la-like determinants did not correlate positively with in vitro cytotoxic function. There is a variable distribution of cytotoxic function among alveolar macrophage density fractions that correlates with enzymatic markers of activation. Differential macrophage activation is a potential determinant of the functional heterogeneity observed in rat alveolar macrophages.