Quantitation of beta2-microglobulin and HLA on the surface of human cells. II. In vitro cell lines and their hybrids.

Beta2-microglobulin (beta2m) participates as an integral part in molecules of the major histocompatibility complex (MHC) type. Absence of beta2m makes the residual heavy MHC chain largely inactive as antigen. Striking reductions in the density per unit surface area of beta2m in seven out of nine malignant lymphoid tumour lines in comparison with normal lymphocytes or "immortalized" Epstein-Barr-virus-transformed lymphoblastoid lines were found is this study. This would seemingly represent a specific reduction in the ability of the malignant cells to express actively produced beta2m, since their HLA antigenic determinants were not reduced to the same extent and no indications were obtained suggesting that free beta2m could transfer from one cell to another. However, that beta2m is important in conveying serological specificities of MHC type to cells was shown by fusion of beta2m-negative and beta2m-positive cells, yielding hybrid cells with synergistically increased numbers of detectable, HLA-related determinants. Whether the reduction of beta2m on malignant versus nonmalignant lymphoid cells bears any relevance as to emergence of the malignant clones and resistance to possible anti-tumour reactions would now be an issue for study.