Functional analysis of complement receptor 1 using a new monoclonal antibody, KuN241.
A monoclonal antibody (MAb), KuN241, recognized an antigen present on all monocytes, polymorphonuclear leukocytes (PMNs), B cells, and a subpopulation of T cells. Cell surface expression pattern and immunoprecipitation studies indicated the molecule recognized by KuN241 to be complement receptor 1 (CR1). This was confirmed by sequential immunoprecipitation using E11, a CR1-specific monoclonal, and by immunoprecipitation analysis of a truncated transfection product of CR1. In vivo activation of PBLs for 7 days with pokeweed mitogen (PWM) abrogated surface expression of CR1 on B cells. Overnight culture with phorbol 12-myristate 13-acetate (PMA) downregulated the expression of CR1 detected by KuN241 both on PMNs and monocytes. Addition of MAb KuN241 to purified PMN and monocytes resulted in a transient increase in intracellular calcium ([Ca2+]i). This was blocked by the Fab fragment of MAb KuFc79 directed against the Fc gamma receptor. Further, Fab fragment of KuN241 cross-linked with F(ab')2 goat anti-mouse Ig failed to increase [Ca2+]i levels. Taken together, these results suggested a novel mechanism for transmembrane signaling events by dual binding of KuN241, the Fab region to CR1 and the Fc region of Fc gamma RII.
Mathew
J M
JM
Department of Surgery, Washington University School of Medicine, St. Louis, Missouri 63110.
Naziruddin
B
B
Duffy
B
B
Krych
M
M
Mohanakumar
T
T
D000818:Animals; D000911:Antibodies, Monoclonal; D001402:B-Lymphocytes / Q000276:immunology; D002118:Calcium / Q000378:metabolism; D015536:Down-Regulation; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D009000:Monocytes / Q000276:immunology / Q000378:metabolism; D009504:Neutrophils / Q000276:immunology / Q000378:metabolism; D017463:Receptors, Complement 3b / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D017452:Receptors, IgG / Q000378:metabolism; D015398:Signal Transduction; D016176:T-Lymphocyte Subsets / Q000276:immunology
D000911:Antibodies, Monoclonal; D017463:Receptors, Complement 3b; D017452:Receptors, IgG; D002118:Calcium