Immunoglobulin D (IgD)-deficient mice reveal an auxiliary receptor function for IgD in antigen-mediated recruitment of B cells.
To assess the role of immunoglobulin D (IgD) in vivo we generated IgD-deficient mice by gene targeting and studied B cell development and function in the absence of IgD expression. In the mutant animals, conventional and CD5-positive (B1) B cells are present in normal numbers, and the expression of the surface markers CD22 and CD23 in the compartment of conventional B cells indicates acquisition of a mature phenotype. As in wild-type animals, most of the peripheral B cells are resting cells. The IgD-deficient mice respond well to T cell-independent and -dependent antigens. However, in heterozygous mutant animals, B cells expressing the wild type IgH locus are overrepresented in the peripheral B cell pool, and T cell-dependent IgG1 responses are further dominated by B cells expressing the wild-type allele. Similarly, in homozygous mutant (IgD-deficient) animals, affinity maturation is delayed in the early primary response compared to control animals, although the mutants are capable of generating high affinity B cell memory. Thus, rather than being involved in major regulatory processes as had been suggested, IgD seems to function as an antigen receptor optimized for efficient recruitment of B cells into antigen-driven responses. The IgD-mediated acceleration of affinity maturation in the early phase of the T cell-dependent primary response may confer to the animal a critical advantage in the defense against pathogens.
Roes
J
J
Institute for Genetics, University of Cologne, FRG.
Rajewsky
K
K
D000818:Animals; D000941:Antigens / Q000276:immunology*; D015703:Antigens, CD / Q000032:analysis; D000944:Antigens, Differentiation, B-Lymphocyte / Q000032:analysis; D001402:B-Lymphocytes / Q000502:physiology*; D015815:Cell Adhesion Molecules; D005260:Female; D007072:Immunoglobulin D / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D037102:Lectins; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D012333:RNA, Messenger / Q000378:metabolism; D016692:Receptors, Antigen, T-Cell, gamma-delta / Q000032:analysis; D017455:Receptors, IgE / Q000032:analysis; D051918:Sialic Acid Binding Ig-like Lectin 2; D013601:T-Lymphocytes / Q000502:physiology
D000941:Antigens; D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; C497868:Cd22 protein, mouse; D015815:Cell Adhesion Molecules; D007072:Immunoglobulin D; D037102:Lectins; D012333:RNA, Messenger; D016692:Receptors, Antigen, T-Cell, gamma-delta; D017455:Receptors, IgE; D051918:Sialic Acid Binding Ig-like Lectin 2