DISTRIBUTION OF ANTI-CD68 (EBM11) IMMUNOREACTIVITY IN FORMALIN-FIXED,PARAFFIN-EMBEDDED BOVINE-TISSUES

A commercially acquired anti-human macrophage antibody (anti-CD68; EBM 11) was used in an immunocytochemical technique to detect macrophages in formalin-fixed, paraffin-embedded tissues from cattle, pigs, humans , rats, turkeys, dogs, and cats. In healthy cattle, the antibody label ed alveolar macrophages, pulmonary intravascular cells (presumably int ravascular macrophages), and macrophage-like cells in other tissues. I n bovine lungs infected with Pasteurella haemolytica, EBM11 antibody l abeled 95% of alveolar macrophages and macrophages within alveolar sep ta but only 0-2% of streaming or ''oat'' leukocytes. Alveolar macropha ges were also stained by EBM11 in pigs but not in rats, turkeys, dogs, and cats. The antibody also stained macrophage aggregates in the mese nteric lymph nodes and intestinal lamina propria of Mycobacterium para tuberculosis-infected cattle. This study shows that the anti-CD68 (EBM 11) antibody is a useful marker of macrophages in normal bovine tissue s or tissues from areas of acute or chronic inflammation that have bee n routinely processed. The study also adds strength to the growing evi dence suggesting that streaming leukocytes seen in pneumonic pasteurel losis are neutrophils.