DIFFERENTIAL AND STRAIN-SPECIFIC TRIGGERING OF BOVINE ALVEOLAR MACROPHAGE EFFECTOR FUNCTIONS BY MYCOPLASMAS

Mycoplasma strains being considered as pathogenic or non-pathogenic fo r cattle were tested on their capacity to activate bovine alveolar mac rophages in vitro. Of particular interest was the behaviour of Mycopla sma mycoides ssp. mycoides small colony type (M.m.m. SC), the causativ e agent of contagious bovine pleuropneumonia (CBPP). Increases in proc oagulant activity (PCA), tumor necrosis factor-alpha (TNF-alpha) and n itrogen monoxide (NO) generation were tested. To minimize an influence of macrophage activation by mycoplasma growth media, mycoplasmas were cultured on embryonic calf nose epithelial cells. The three macrophag e functions tested were not correlated, but were differentially induce d in strain-specific manner. Four out of seven strains induced PCA, re gardless of pathogenicity, and all strains promoted moderate NO genera tion at high concentrations. All tested M.m.m. SC strains (Afade, L2 a nd PG1), and the pathogenic M. bovis, induced TN F-alpha production at low concentrations (10(6) colony forming units per ml). M. sp. serogr oup 7 and the non-pathogenic n/l. bovirhinis and Acholeplasma laidlawi i did not induce TNF-alpha: up to 10(8) cfu/ml. Thus, strain-specific differences are reflected in differential macrophage activation patter ns. The findings are consistent with an important role for TNF-alpha i n pathogenesis of CBPP. (C) 1996 Academic Press Limited