Ultrastructural, histochemical and immunohistochemical features of porcine intestinal lamina propria macrophages, peripheral blood monocytes and splenic adherent cells.

Ultrastructural, histochemical and immunohistochemical features of porcine intestinal lamina propria macrophages (LPMs), peripheral blood fibronectin-adherent cells (FACs) and splenic-adherent cells (SPACs) were compared. Freshly isolated FACs and SPACs were small and showed small cytoplasmic processes, little evidence of endocytic vacuoles, few lysosomes and sparse rough endoplasmic reticulum (RER). Fresh FACs were negative for acid phosphatase, non-specific esterase (NSE) and beta-galactosidase activity. Of the SPACs, 20-40% were positive for acid phosphatase, < 5% for NSE and 5-10% for beta-galactosidase. Pre-cultured FACs and SPACs were large and showed an abundance of endocytic vacuoles; they possessed dilated and prominent RER and > 95% were positive for the three enzyme activities. LPMs exhibited abundant endocytic vacuoles or vesicles and lysosomes but sparse RER, and > 85% were positive for the three enzymes. LPMs (24%), FACs (49%) and SPACs (40%) expressed MHC (major histocompatibility complex) class II glycoproteins. Macrophage-granulocyte antigens were detected in LPMs (14%), FACs (50%) and SPACs (33%). The results thus suggest that freshly isolated FACs differ from LPMs morphologically and in enzymic features, and the differences may represent part of the cell maturation process.