Common antigenic structures of HLA antigens. VII. Selective combination binding of beta2-microglobulin with HLA large component in cultured human cell lines.

The intracellular distribution of human beta2-microglobulin was examined in human cell lines (a Burkitt lymphoma cell line, a B-lymphoid cell line and an epighelial-like cell line). Freshly harvested cells were mechanically disrupted and separated into the nuclear, cell-membrane and cell-sap fractions. Nearly 90 per cent of the total beta2-microglobulin was recovered in the cell-membrane and cell-sap fractions. The cell-membrane fraction contained 75-88 per cent of the beta2-microglobulin recovered. The rest was in the cell-sap fraction. Most, 84-91 per cent, of the beta2-microglobulin in the cell-membrane fraction was present combined with membrane fraction was present combined with membrane components of about 38,000 daltons that carried the xenoantigenic activity characteristic of the HLA large component. These membrane components did carry HLA alloantigenic activity. No other membrane components were involved in binding beta2-microglobulin. The beta2-microglobulin in the cell-sap fraction was present in the unbound state. Thus, in the cell lines examined, the membrane component which was combined with beta2-microglobulin appeared to be exclusively the HLA large component and no larg excess of beta2-microglobulin over the HLA large component was found.