Detection and isolation of an Ia glycoprotein antigen from mouse serum

Partial purification and characterization of chicken immune-associated antigen in serum coded for by the major histocompatibility complex

Chicken serum contains 3 molecular species of immune-associated (Ia) antigen coded for by the major histocompatibility complex (MHC). These molecules are named B-L alloantigens [1]. They vary in electrophoretic migration velocity and molecular size [2]. The aim of this study was to characterize one of the antigen species - the low molecular size form. Therefore, we performed a partial purification by: (i) affinity chromatography; and (ii) ammonium sulfate precipitation of serum B-L antigen from the chicken plasma. Since the MHC-antigens were known to be glycoproteins, the purification was based on lectin affinity chromatography, as previously used for the membrane-bound MHC-antigens [3]. Electro-immunochemical analysis using rabbit antibodies against the chicken lymphocyte plasma membrane and the partially purified antigen were employed to monitor the purification and to characterize the different molecular forms of the Ia molecules. The partially purified preparation was then analyzed to elucidate the biochemical structure of the serum B-L antigen. Finally, rabbit antiserum was raised against this preparation to evaluate its level of purity and to follow further purification of this molecule.

Immunological tolerance in the chicken. III. Partial physiochemical characterization of two suppressive fractions from serum of chickens tolerant to bovine serum albumin

Two soluble non-specific suppressive factors were isolated by gel chromatography from the serum of chickens tolerant to bovine serum albumin (BSA). Fraction I was found by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) to contain five proteins with mol. wts from 200,000 to 900,000 unreduced and six proteins that ranged from 70,000 to 180,000 when reduced. The composition was primarily protein, with a small amount of carbohydrate and lipid. One component was identified as IgM, one as a lipoprotein. The others remain unidentified. No evidence of the tolerogen, BSA, was found. The second factor, fraction III of both tolerant and normal serum, was found by SDS-PAGE to have two proteins with mol. wts of 54,000 and 78,000 in the unreduced form and contained a very small amount of protein, a large amount of carbohydrate, and no detectable lipid. Normal fraction III had two proteins with mol wts of 54,000 and 65,000 when reduced, whereas reduction did not affect tolerant fraction III. A soluble suppressive factor, secreted by cultured adherent cells of tolerant chickens, was found to be comparable to fraction III in molecular weight. Comparison of these results with those of other reported suppressive factors is made and possible identities of the suppressive components of fractions I and II are discussed.

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.