Lymphotoxin and Class II HLA-DR Co-Precipitate?

Lymphotoxin (TNFβ), not usually present in resting peripheral blood lymphocytes, is detectable in the cytoplasm but not the cell membrane of EBV-transformed cell lines (LCLs). A 25 kD band was clearly visible from anti-DR immunoprecipitates of LCLs after SDS-PAGE analysis. A corresponding band was found after immunoprecipitates of the same LCL with anti-lymphotoxin monoclonal antibody (MAb). Immunodepletion studies with the DR and anti-lymphotoxin MAbs indicated that the two fragments were one and the same and that DR and lymphotoxin co-precipitate with the anti-DR MAb but not with the lymphotoxin MAb. This observed lymphotoxin response to virus infection and co-precipitation with class II molecules and its known effect on class II expression suggests that it may play a regulatory role in the pathogenesis of HLA-associated disorders of putative viral etiology.