Characterization of a 75,000 mol. wt glycoprotein synthesized by guinea-pig T-lymphocytes: a possible homologue of Lyt-1 antigen

Chicken thymocyte-specific antigen identified by monoclonal antibodies: ontogeny, tissue distribution and biochemical characterization

Two monoclonal antibodies, CT-1 (IgG1, kappa) and CT-1a (IgG3, kappa) were prepared against chicken thymocytes. The antigen identified by these antibodies was found to be a glycoprotein with a major polypeptide component having an apparent molecular weight of 63 000 and a minor polypeptide component of approximately 103 000. Immunoprecipitation and blocking experiments revealed that the two antibodies react with different antigenic determinants of the molecule. Ontogenic studies employing immunofluorescence failed to reveal the antigenic determinants on cells from the embryo or embryonic yolk sac on days 3 and 6 of incubation. The number of embryonic thymocytes bearing the molecules detected by these antibodies increased from 6% on day 12 to 54% on day 13; the frequency of thymocytes expressing this glycoprotein reached adult levels (greater than 90%) by the 15th day of embryonic age. In contrast, the CT-1 and CT-1a antibodies reacted with only 2-5% of blood and splenic cells and less than 0.05% of cells from bursa or bone marrow of young adult chickens. In the quail CT-1 reacted with cortical, but not medullary, thymocytes, while the CT-1a antibody was unreactive with quail thymocytes. The surface glycoproteins detected by these discriminating monoclonal antibodies may provide an important discriminating marker for thymic lymphocytes in the chicken and the quail.

Identification of a sulfate-bearing molecule associated with HLA class II antigens

The human Ia antigens (DR, DS, and SB), determined by genes contained within the HLA complex on chromosome 6, are glycoprotein heterodimers consisting of a Mr approximately equal to 34,000 alpha chain and a Mr approximately equal to 28,000 beta chain. As a result of studies exploring the possibility that alpha or beta (or both) might be sulfated, a unique component of the oligomeric Ia antigen complex was discovered. When anti-Ia immunoprecipitates from Nonidet P-40 lysates of [35S]sulfate-labeled lymphoid cells were analyzed by NaDodSO4/PAGE, a molecule of considerable size heterogeneity (Mr 40,000-70,000) was observed. This component was present in both anti-DR and anti-DS immunoprecipitates prepared from both human tonsil cells and lymphoblastoid B-cell lines but was not observed in control precipitates or in association with immunoglobulin or class I HLA molecules. Preliminary biochemical studies indicate that this Mr 40,000-70,000 molecule is polyanionic, disperse in molecular weight, and sensitive to protease digestion. The sulfate-bearing moiety of this component was resistant to Pronase but sensitive to chondroitinase ABC, indicating that this molecule belongs to the chondroitin sulfate class of proteoglycans.