ABERRANT EXPRESSION OF HLA CLASS-I ANTIGENS IN BURKITT-LYMPHOMA CELLS

HLA class-I expression has been investigated by biochemical methods in 14 Burkitt lymphoma (BL) cell lines and the corresponding Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines (LCL) derived from the same individuals. Selective down-regulation of one or more HLA class-I specificities was demonstrated in 9 out of 14 BL lines. The defect was restricted to a single HLA-A allele in 3 of the lines (BL29, BL72, WW-I-BL). Four lines (BL28, BL37, BL41 and Jijoye M13) showed down-regulation of both HLA-A and -C alleles, and one (BL36) failed to express one HLA-C allele. Only one BL line (WW-2-BL) had lost one HLA-A and one HLA-B allele. The allele-specific defects were mainly detected in cell lines that had maintained the phenotypic characteristics of the original tumor. Expression of B-cell activation markers and the EBV-encoded nuclear antigen (EBNA)-2 correlated with up-regulation of the Cw4 allele in the P79 subline of the BL line Jijoye. Treatment with gamma-interferon (IFN) resulted in full or partial reversion of the HLA class-I defects in some of the cases but had no significant effect in others. This was not due to a cell-line-related unresponsiveness to IFN, nor did it reflect an allele-specific mode of regulation because the same allele could respond differently in different cell lines. The data suggest that defective expression of HLA class-I antigens, which appears to be more prevalent for alleles within the HLA-A and -C loci, is a common feature of BL cell lines. Different regulatory mechanisms appear to be involved.