DIFFERENTIAL INFECTION OF PORCINE ALVEOLAR MACROPHAGE SUBPOPULATIONS BY NONOPSONIZED MYCOBACTERIUM-BOVIS INVOLVES CD14 RECEPTORS

The resurgence in mycobacterial infection worldwide has led to renewed attention to the pathogenesis of Mycobacterium species, The purpose o f this study was to characterize the infection of alveolar macrophages (AMs) by nonopsonized Mycobacterium bovis, and to elucidate the mecha nism by which a differential infection of subpopulations of AM may occ ur. ih difference in susceptiblity to Mycobacterium bovis infection of subpopulations of AMs was observed, such that the least dense cells w ere the least susceptible (21.4 +/- 10.7%) and the most dense cells we re tile most readily infected (61.8 +/- 5.6%), The percentage of AMs s taining for CD14 receptors showed a similar differential distribution, with fewer of the lease dense cells expressing CD14 and a greater per centage of the most dense cells staining for CD14 receptor expression, To investigate the role of CD14 receptors in tile infection of AMs, a nti-CD14 antibody was added to the cell cultures, infection of AM by M ycobacterium bovis was blocked by up to 60.2% by anti-CD14 antibody hu t not by isotype control antibody, The results of this study suggest t hat Mycobacterium bovis selectively infects AM subpopulations, specifi cally those with the greatest expression of CD14, a putative receptor mechanism for Mycobacterium bovis infection of porcine AM.