Differential surface expression and possible function of 9-O- and 7-O-acetylated GD3 (CD60 b and c) during activation and apoptosis of human tonsillar B and T lymphocytes
The disialoganglioside GD3 (CD60 a) and its O-acetylated variants have previously been described as surface molecules of human T lymphocytes of the peripheral blood system. Here we report the expression of the 9-O-, and 7-O-acetylated disialoglycans of GD3 (CD60 b and CD60 c respectively) on human tonsillar lymphocytes. CD60 b and c are surface-expressed on activated germinal centre B cells and colocalize in raft-like structures on the cell surface together with the cytoplasmic tyrosine kinase Lyn and Syk. Addition of CD60 b and c mAb together with anti-IgM/IL-4 to in vitro cultivated tonsillar B cells resulted in a costimulatory effect. During spontaneous and staurosporine-induced apoptosis a distinct population of activated annexin V+/CD60 b+/CD60 c- B cells was observed. CD60 b and c are also found on cells of the extrafollicular T cell area. On tonsillar T cells, CD60 b mAb had a costimulatory effect together with PHA while CD60 c mAb alone was sufficient to induce proliferation. In further contrast to B cells, during apoptosis a distinct CD60 b+ T cell subpopulation was not observed. Together, surface-expressed CD60 b and c are differently expressed on tonsillar B and T cells and may be involved in the regulation of activation and apoptosis of lymphocytes in secondary lymphatic tissue.
KeywordsGanglioside Germinal center Lipid rafts O-acetylated sialic acid Signal transduction
bovine serum albumin
cholera toxin subunit B
fetal calf serum
laser scan microscopy
phosphate buffered saline
Vibrio cholerae sialidase
We sincerely thank Dr. H. Spring, DKFZ, Heidelberg for performing the confocal laser scan microscopy of this study and Dr. R. Schauer, University of Kiel for critical reading of the manuscript.
This study was financially supported by the Tumorzentrum Heidelberg/Mannheim and a grant of the Deutsche Forschungsgemeinschaft (DFG) to R.S.-A. (Schw 381/4-1).
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