CD19 is functionally and physically associated with surface immunoglobulin.
The pan-B and B cell-specific sIg and CD19 antigens are functionally and physically associated in the presence of anti-Ig mAb. Incubation of B cells with anti-Ig antibodies causes rapid, specific, reversible, concentration-dependent, and unidirectional comodulation of CD19 on every mature B cell studied. Comodulation is produced by mAbs specific for the gamma, mu, kappa, and lambda chains of Ig, and by at least one idiotype-specific mAb. Comodulation is observed using 15 CD19-specific mAbs that detect at least three different CD19 epitopes. Of 18 surface antigens studied, only CD19 is comodulated. Loss of sIg and CD19 occurs concurrently during anti-Ig modulation and demonstrates a comparable dependence on anti-Ig concentration, suggesting that these are parallel rather than serial events. Incubation with anti-Ig specifically cocaps and suggests internalization of anti-CD19 mAb. Comodulation of sIg and CD19 by anti-Ig but not anti-CD19 mAbs suggests that ligand binding enables sIg to then interact with CD19. We propose that CD19 is a component of the B cell antigen receptor and suggest that it could facilitate signal transduction by sIg-antigen complexes.
Pesando
J M
JM
Biomembrane Institute, Seattle, Washington 98119.
Bouchard
L S
LS
McMaster
B E
BE
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D018941:Antigens, CD19; D000944:Antigens, Differentiation, B-Lymphocyte / Q000502:physiology*; D001402:B-Lymphocytes / Q000276:immunology*; D051379:Mice; D011947:Receptors, Antigen, B-Cell / Q000502:physiology*; D015398:Signal Transduction
D000911:Antibodies, Monoclonal; D018941:Antigens, CD19; D000944:Antigens, Differentiation, B-Lymphocyte; D011947:Receptors, Antigen, B-Cell