Immunohistochemical distribution of S-100 α-positive cells in bovine mycobacterial and non-mycobacterial granulomas

Summary By means of immunohistochemistry, the distribution of the α-subunit (S-100α) and the β-subunit (S-100β) of S-100 protein was studied in bovine granulomas caused by Actinomyces bovis , Actinobacillus lignieresi , Actinomyces ( Corynebacterium ) pyogenes , Pseudomonas aeruginosa , Staphylococcus aureus , Mycobacterium bovis and Mycobacterium paratuberculosis . S-100α-positive epithelioid cells or dendritic cells were scattered among the predominantly S-100α-negative cells of the mononuclear phagocyte system (MPS). S-100β was not found in the MPS cells of granulomas but was observed in the endothelial cells of blood vessels. A positive reaction to S-100 was also seen in normal cells in the lymphoid and mammary tissues. Mycobacterial granulomas contained more S-100α-positive cells than did non-mycobacterial ones.