ELECTRON-MICROSCOPIC ANALYSIS OF THE NORMAL AND THE ACTIVATED PLEURALMACROPHAGE

Despite an apparent role in pleural pathophysiology, little informatio n is known about pleural macrophage morphology. Intrapleural tetracycl ine (TCN) results in pleural macrophage influx and pleural fibrosis; i ntrapleural carrageenan (CAR) induces macrophage influx without ensuin g fibrosis. Pleural macrophages collected from normal (NL) and TCN- or CAR-exposed rabbit pleural spaces were examined with electron microsc opy. Cellular size; number of microvilli; pseudopods; coated pits (CP) and coated vesicles (CV); and prevalence of golgi, rough endoplasmic reticulum (RER), and intermediate filaments (IF) were determined. The means of each variable in each group were assessed by one-way analysis of variance, with post boc testing performed by Scheffe F test; p les s-than-or-equal-to 0.5 was considered significant. TCN-stimulated pleu ral macrophages were characterized by their small perimeters. CAR-indu ced pleural macrophages were marked by their large size and abundant i ntracellular amorphous material. They bad larger perimeters, areas, an d diameters than the TCN-induced or normal macrophages and thus smalle r numbers of CV + CP per area. The normal pleural macrophages were cha racterized by more IF, microvilli, and microvilli per perimeter than e ither the CAR- or TCN-induced pleural macrophages. No differences betw een groups were found in nuclear cytoplasmic ratios, number of pseudop ods, and content of golgi or of RER. The results suggest that normal p leural macrophages and TCN- and CAR-induced pleural macrophages differ morphologically and that these morphologic differences reflect functi onal differences.