Identification of pregnancy-associated alpha-macroglobulin on the surface of peripheral blood leucocyte populations

Pregnancy-associated alpha-macroglobulin (PAM) was identified on the surface membranes of human peripheral blood leucocytes by immunofluorescent staining. Subjects having a high serum-level of the glycoprotein (pregnant and contraceptive steroid-treated women) were shown to possess a significantly greater proportion of PAM-positive cells than those (normal males) with a low concentration. However, no correlation was found between the serum values and the percentage of PAM-associated leucocytes. Studies employing purified leucocyte-types and the simultaneous detection of PAM and lymphocyte surface markers indicated that only subpopulations of T lymphocytes (23%) and monocytes (40%) were associated with this serum protein.