The large sialoglycoprotein of human lymphocytes

• L-LSGP is an abundant cell surface glycoprotein (a.m.w. intact 115—125 kdalton, desialylated 140—160 kdalton) restricted to lymphocytes in the hemopoietic system. The desialylated molecule can be selectively detected and isolated by the snail agglutinin, Helix pomatia A hemagglutinin after labeling of cell surface components, affinity chromatography to lectin- Sepharose, SDS-PAGE and autoradiography. Similarly, the intact molecule can be specifically isolated by Maclura pomifera agglutinin.Monospecific antibodies directed against desialylated L-LSGP of peripheral blood lymphocytes were produced in chicken and used in indirect immunofluorescence to investigate the distribution of L-LSGP among hemopoietic subsets. Circulating blood T cells contain considerably higher amounts of a more sialylated form of the molecule than thymocytes. The majority (90%) of mitogen activated T cell blasts bear L-LSGP. In contrast, about 50% of alloantigen activated (mixed leucocyte culture) T cell blasts bear L-LSGP. LLSGP is present on virtually all thymocytes and peripheral blood T cells. A subpopulation (25%) of normal blood and umbilical cord blood B cells also carry L-LSGP. Studies of different monoclonal B cell populations representing different stages in B cell ontogeny reveal the presence of both L-LSGP+ and L-LSGP- populations within each of the stages. Hence, L-LSGP+ B cells may represent a separate lineage within the B cell compartment.Analysis of amino acid composition and tryptic degradation patterns of L-LSGPs from thymocytes and peripheral blood lymphocytes of normal adults and B-CLL patients show that the molecules are closely related. The L-LSGPs are highly glycosylated, containing about 50% (w/w) carbohydrate. Most carbohydrate is probably 0-glycosidically linked to the peptide.L-LSGP appears to be a conservative molecule showing very little species specificity in mammals. Rabbit, rat and mouse lymphocytes contain a very similar glycoprotein. The function of L-LSGP is unknown. It is suggested that L-LSGPs may have an important role to maintain cell integrity during the circulatory life of the lymphocyte.

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NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

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