THE PHENOTYPE AND PHAGOCYTIC-ACTIVITY OF MACROPHAGES DURING MAEDI-VISNA VIRUS-INFECTION

Macrophages from maedi-visna virus (MVV) infected sheep have been show n to have an activated phenotype from sites of lesions in vivo, Here w e have looked at the direct effect of virus infection on macrophage ph enotype and activity in vitro by flow cytometry, There was no signific ant difference in the expression of several surface markers (CD4, CD8, MHC Class I, MHC Class II, lymphocyte function associated antigen(LFA )-1 and LFA-3) on monocyte-derived macrophages (MDM) by 5 days post MV V infection. In contrast the phagocytic activity of MVV-infected MDM f or the yeast Candida utilis and erythrocytes was decreased by 5 days p .i. although the surface binding of erythrocytes was not affected. Int erestingly, an activated phenotype was seen on alveolar macrophages (A M) from sheep with maedi (surface expression of MHC Class I, Class II and LFA-1 was increased), but there was no difference in the binding a nd phagocytosis of erythrocytes by these cells. However the binding an d phagocytosis of the bacterium, Pasteurella hemolytica was increased with AM from MVV-infected sheep without lesions. Similarly there was n o significant difference in the phagocytic and erythrocyte resetting a ctivity between fresh monocytes from MVV-infected and uninfected contr ol sheep. Therefore the phenotype of macrophages taken from sites of l esions caused by MVV does not correspond to a direct effect by the vir us on these cells or to particular activities of the macrophages.