Early steps of IgA B cell differentiation.
The overall picture of IgA B cell differentiation to emerge from these studies is that sIgM-bearing 'virgin' B cells entering the Peyer's patches are subject to a microenvironment (most probably organ-specific stromal cells) which brings about initial or primary IgA switch differentiation. For reasons mentioned, this probably does not involve TGF-beta, which instead appears to operate on a cell, such as the CH12.LX B cell, which has already undergone the initial steps of IgA isotype switching. The next stage of IgA B cell differentiation involves a cell which expressed both sIgM and sIgA simultaneously and appears to produce C mu and C alpha mRNA transcripts in the absence of a deletional rearrangement. Whether this involves a 'transplicing' mechanism or some other mechanism has yet to be determined. Finally, committed IgA B cells emerge from the dual-bearing cell population which express only sIgA. These cells can migrate out of Peyer's patches and respond to various terminal differentiation factors such as IL-5, IL-6 and IFN-gamma.
Strober
W
W
Mucosal Immunity Section, LCI, National Institute of Allergy and Infectious Diseases, Bethesda, Md.
Harriman
G R
GR
Kunimoto
D R
DR
D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology* / Q000276:immunology*; D002454:Cell Differentiation; D007070:Immunoglobulin A / Q000096:biosynthesis* / Q000235:genetics; D007075:Immunoglobulin M / Q000096:biosynthesis / Q000235:genetics; D007134:Immunoglobulin Switch Region; D008213:Lymphocyte Activation; D051379:Mice; D016212:Transforming Growth Factor beta / Q000494:pharmacology
D007070:Immunoglobulin A; D007075:Immunoglobulin M; D016212:Transforming Growth Factor beta