Lymphocyte subpopulations in the blood of sheep persistently infected with border disease virus

The surface phenotypes of peripheral blood lymphocytes in groups of lambs and adult sheep persistently infected with Border disease virus (P-I BD) were compared with those of healthy controls. The proportion and number of lymphocytes bearing surface immunoglobulin (sIg+) and expressing class II MHC antigen (B cells) were significantly increased. A significant increase in CD1+ lymphocytes was also evident. Conversely, the proportion of T lymphocytes in P-I BD lambs was reduced. A marked reduction in the proportion of circulating lymphocytes expressing class I MHC antigen was also observed. These findings were not affected by differences in the strain of the virus responsible for the persistent infection.