Surface expression of immunoglobulin isotypes on primary human B cells: no evidence for glycosyl-phosphatidylinositol linkage.
Surface expression of membrane(m) IgM molecules requires the association of two disulphide-linked transmembrane (TM) glycoproteins, encoded by the B-cell-specific genes mb-1 and B29. We have shown that mIgM, mIgD and mIgG are associated with structurally related heterodimers on primary human B cells. Transfection studies in murine plasmacytoma cells, however, have demonstrated mb-1-independent expression of both mIgD and mIgG. The recent finding that mIgD is expressed on these cells through glycosyl-phosphatidylinositol (GPI) linkage may be interesting in view of the function of mIgD on primary B cells. We therefore investigated whether GPI linkage serves as an additional mechanism for expression of mIgD and the other mIg isotypes on primary human B cells. However, we were unable to demonstrate the release of mIg molecules upon treatment with phosphatidylinositol-specific phospholipase C (PI-PLC) in either immunofluorescence analysis or Ig heavy (H) chain-specific enzyme-linked immunosorbent assay (ELISA). We conclude that primary human B cells, which constitutively express the mb-1 and B29 genes, do not express the mIg isotypes in a GPI-linked manner.
Lankester
A C
AC
Department of Clinical Viro-Immunology, Central Laboratory of the Netherlands Red Cross Blood Transfusion Service, Amsterdam.
van Noesel
C J
CJ
van Schijndel
G M
GM
van Lier
R A
RA
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D002460:Cell Line; D002462:Cell Membrane / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D017261:Glycosylphosphatidylinositols / Q000276:immunology*; D007072:Immunoglobulin D / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology; D007075:Immunoglobulin M / Q000276:immunology; D007136:Immunoglobulins / Q000276:immunology*; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D054801:Phosphoinositide Phospholipase C; D010727:Phosphoric Diester Hydrolases / Q000276:immunology
D017261:Glycosylphosphatidylinositols; D007072:Immunoglobulin D; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D007136:Immunoglobulins; D010727:Phosphoric Diester Hydrolases; D054801:Phosphoinositide Phospholipase C; D043265:Phosphatidylinositol Diacylglycerol-Lyase