In search of alpha 1-microglobulin on the lymphocyte surface

alpha 1-Microglobulin was found by immunofluorescence not to be associated with human lymphoid and nonlymphoid cell lines. No accumulation of alpha 1-microglobulin was detected in culture media of these cell lines. A weak membrane fluorescence with anti-alpha 1-microglobulin on peripheral lymphocytes could not be blocked by the purified protein. No release of alpha 1-microglobulin into the growth medium was seen by normal cultured leukocytes. Treatment of normal lymphocytes, erythrocytes, and various cell lines with solubilization techniques did not yield any alpha 1-microglobulin. alpha 1-Microglobulin and protein HC display immunologic and biochemical identity. However, anti-protein HC stained almost all of the tested cell lines and normal lymphocytes. Blocking experiments with the purified protein were not successful. Antibodies reacting with a minor impurity (50,000 d) in the alpha 1-microglobulin or protein HC preparations could be absorbed from anti-alpha 1-microglobulin with normal leukocytes and a lymphoid cell line.