Studies on the Cytophilic Properties of Human β2-Microglobulin

The mechanism by which exogenously added beta2m binds to lymphoid cells has been explored. In the mouse it has been shown that beta2m remains associated with plasma membrane macromolecules following solubilization with NP-40 and that approximately 25-30% of the binding could be accounted for by binding to H-2 antigens. No binding to mouse immunoglobulin or Ia antigens could be detected. The sites for binding of the remainder of the cell-bound beta2m were not determined. Whereas normal human lymphocytes showed little or no capacity to bind exogenously added beta2m, it was found that phytohaemagglutinin (PHA)-stimulated cells could bind beta2m. This binding occurred optimally 2 days after PHA stimulation. Approximately half of the binding could be accounted for by binding to HLA antigens. The possible significance of these findings with respect to cellular interactions involving major histocompatibility complex gene products in the immune response is discussed.