Induction of HLA expression in Daudi cells after cell fusion

The Daudi cell line, established from a Burkitt lymphoma, has recently been found to be HLA- and Β₂-microglobulin-negative, although it expresses B lymphocyte alloantigens. This report is concerned with the reexpression of HLA-A10, B38, and B17 on the Daudi cell, after cell fusion with another human cell line (Raji) or with mouse fibroblasts. In the latter fusion, the same HLA specificities are re-expressed, but not human Β₂-microglobulin while mouse Β₂-microglobulin and H-2 could be detected. No such reexpression was observed when Daudi was fused with the F9 mouse teratocarcinoma, which lacks mouse Β₂-m and H-2. No HLA activity (alloantigenic and xenogenic activity) was detected in the membrane or cytoplasm of Daudi, using salt extraction and sonication. Therefore we postulate that Β₂-microglobulin could be necessary for the expression and possible synthesis of the HLA antigen.