Expression of virus-specific, thymus-specific and tumour-specific antigens in lymphoblastoid cell lines derived from Marek's disease lymphomas.

Abstract

SUMMARY The expression of virus, thymus and tumour-specific antigens was studied in two Marek’s disease lymphoblastoid cell lines (MSB-1 and HPRS-line 2). The proportions of cells which spontaneously expressed virus antigens or which formed infective centres in vitro were considerably higher in MSB-1 than in HPRS-line 2, but did not exceed 10%. In contrast to virus antigens, thymus-specific and tumour-specific antigens were expressed on the majority of the cells. Treatment with IdUrd increased the proportion of cells forming infective centres in both cell lines and the proportion of cells expressing virus antigens in MSB-1. A decline in the proportion of cells forming infective centres in IdUrd-treated and in untreated cultures was noted during continuous subculture of both cell lines. Direct evidence for the presence of virus-specific antigens in MSB-1 cells was obtained by immunodiffusion. The results suggested further that lymphoblastoid cells are unable to synthesize a major precipitating glycoprotein antigen (A antigen) normally associated with infection of permissive cells with MDV. Analysis of surface proteins of normal thymus cells labelled by lactoperoxidase-catalysed iodination showed that thymus-specific determinants are associated with iodinated polypeptides in the mol. wt. range 45000 to 47000, 50000 to 58000 and 90000 to 150000. The major thymus-specific polypeptide exposed at the surface of normal thymus cells was in the mol. wt. range of 50000 to 58000. Surface proteins of lymphoblastoid cells were not accessible to iodination.