Relationship of pregnancy-associated alpha2-glycoprotein (alpha2-PAG) to peripheral blood leucocytes

The high molecular weight plasma glycoprotein pregnancy-associated alpha2-glycoprotein (alpha2-PAG) can be demonstrated on the surface of blood leucocytes and is synthesized by oestrogen-stimulated cells in culture. By the use of an indirect immunofluorescence technique, pretreatment of leucocytes with anti-alpha2-PAG IgG revealed alpha2-PAG on C3 rosette-forming cells and monocytes but not on E rosettes. Lymphocytes treated with anti-alpha2-PAG showed markedly diminished ability to form Fc rosettes. A percentage ranging from 15% to 20% of leucocytes from normal adults of both sexes, pregnant and oestrogen-treated females were positive for alpha2-PAG but no obvious correlatin was observed between the incidence of alpha2-PAG bearing cells and plasma levels of the protein.