Molecular relationships between large membrane proteins (LMP) expressed on T and B lymphocytes

Clones prepared from day 5 mixed lymphocyte cultures (MLC) were examined for the expression of large (170,000- to 200,000-dalton) membrane proteins (LMP), found on bulk cultures of resting and allogeneically activated T lymphocytes. Sodium dodecyl sulfate-poly-acrylamide gel electrophoresis (SDS-PAGE) of these proteins indicates both bulk populations and noncytotoxic clones express LMP of similar m.w. Peptide mapping further indicates that LMP of 187,000 (187K) and 200K daltons, found on T cells from bulk cultures or clones and the 220K dalton LMP from B cells, all appear to have a very similar peptide composition. This suggests a single protein (or series of closely related proteins) is differentially processed in functionally disparate populations, and hence may serve as a differentiation antigen for these populations.