Enhancement and suppression of signaling by the conserved tail of IgG memory-type B cell antigen receptors.
Immunological memory is characterized by heightened immunoglobulin (Ig) G antibody production caused in part by enhanced plasma cell formation conferred by conserved transmembrane and cytoplasmic segments in isotype-switched IgG B cell receptors. We tested the hypothesis that the IgG tail enhances intracellular B cell antigen receptor (BCR) signaling responses to antigen by analyzing B cells from Ig transgenic mice with IgM receptors or chimeric IgMG receptors containing the IgG tail segment. The IgG tail segment enhanced intracellular calcium responses but not tyrosine or extracellular signal-related kinase (ERK) phosphorylation. Biochemical analysis and crosses to CD22-deficient mice established that IgG tail enhancement of calcium and antibody responses, as well as marginal zone B cell formation, was not due to diminished CD22 phosphorylation or inhibitory function. Microarray profiling showed no evidence for enhanced signaling by the IgG tail for calcium/calcineurin, ERK, or nuclear factor kappaB response genes and little evidence for any enhanced gene induction. Instead, almost half of the antigen-induced gene response in IgM B cells was diminished 50-90% by the IgG tail segment. These findings suggest a novel "less-is-more" hypothesis to explain how switching to IgG enhances B cell memory responses, whereby decreased BCR signaling to genes that oppose marginal zone and plasma cell differentiation enhances the formation of these key cell types.
Horikawa
Keisuke
K
Immunogenomics Laboratory, The Australian Phenomics Facility, The John Curtin School of Medical Research, The Australian National University, Canberra 0200, Australia.
Martin
Stephen W
SW
Pogue
Sarah L
SL
Silver
Karlee
K
Peng
Kaiman
K
Takatsu
Kiyoshi
K
Goodnow
Christopher C
CC
D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002454:Cell Differentiation; D017124:Conserved Sequence; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D007075:Immunoglobulin M / Q000276:immunology; D007156:Immunologic Memory / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D019000:Phosphotyrosine / Q000378:metabolism; D011947:Receptors, Antigen, B-Cell / Q000737:chemistry* / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D017452:Receptors, IgG / Q000737:chemistry* / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D051918:Sialic Acid Binding Ig-like Lectin 2 / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology; D015533:Transcriptional Activation
D007075:Immunoglobulin M; D011947:Receptors, Antigen, B-Cell; D017452:Receptors, IgG; D051918:Sialic Acid Binding Ig-like Lectin 2; D019000:Phosphotyrosine; D048049:Extracellular Signal-Regulated MAP Kinases; D002118:Calcium