The membrane IgM-associated heterodimer on human B cells is a newly defined B cell antigen that contains the protein product of the mb-1 gene.
7/8embrane IgM (mIgM) on human B lymphocytes is noncovalently associated with a disulfide-linked dimer that contains phosphoproteins of 47 and 37 kDa. In this study, the biochemical properties and the identity of these Ag receptor-associated components have been addressed. Both subunits carry N-linked carbohydrate groups. After deglycosylation, the 47-kDa and 37-kDa proteins have similar molecular masses, of about 23 kDa, and relatively acidic but different isoelectric points. The accumulated data, together with a previously performed comparison of tryptic peptides, suggest that the two components are structurally distinct and possibly encoded by different genes. Indeed, a mAb, raised against a synthetic peptide that was made on the basis of the published carboxyl-terminal amino acid sequence of the human mb-1 gene product, specifically reacted with the 47-kDa but not the 37-kDa subunit. None of the established B cell-specific mAb characterized in the Fourth International Workshop on Leukocyte Antigens, including CD24, CD37, and CD72, detect the mIgM-linked heterodimer, which makes it a newly defined human B cell Ag.
van Noesel
C J
CJ
Central Laboratory of The Netherlands Red Cross Blood Transfusion Service, Amsterdam.
van Lier
R A
RA
Cordell
J L
JL
Tse
A G
AG
van Schijndel
G M
GM
de Vries
E F
EF
Mason
D Y
DY
Borst
J
J
D015703:Antigens, CD / Q000032:analysis; D000954:Antigens, Surface / Q000032:analysis*; D001402:B-Lymphocytes / Q000276:immunology*; D051925:CD79 Antigens; D002460:Cell Line; D006031:Glycosylation; D006801:Humans; D007075:Immunoglobulin M / Q000032:analysis*; D008562:Membrane Glycoproteins / Q000032:analysis* / Q000235:genetics; D008970:Molecular Weight; D011947:Receptors, Antigen, B-Cell
D015703:Antigens, CD; D000954:Antigens, Surface; D051925:CD79 Antigens; C497881:CD79A protein, human; D007075:Immunoglobulin M; D008562:Membrane Glycoproteins; D011947:Receptors, Antigen, B-Cell