Biochemical comparison of HLA-DR molecules derived from autologous human T and B lymphoblasts

Earlier findings that human activated T blasts display HLA-DR determinants have been confirmed. After phytohemagglutinin activation, Percoll gradient-purified blast cells were cultured for two weeks in mitogen-derived supernatants from human lymphocyte cultures. Using purified T blasts and internal labeling procedures, it was established that T blasts actively produced HLA-DR-like chains, as assessed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Further, HLA-DR chains obtained from Epstein-Barr virus-transformed B cells and from T blasts of the same donor were compared. Two-dimensional gel electrophoretic comparisons indicated a striking homology between 29 kD and 35kD chains, obtained from the two different cell types. Peptide map analysis and preliminary amino acid sequence comparisons further supported this similarity. A more complete analysis would, however, be required to prove actual identity. The fact that human T blasts produce and display HLA-DR molecules very similar, if not identical, to those present on B cells must then be incorporated into models discussing major histocompatibility complex-restricted collaborations involving HLA-DR molecules.