Differential regulation of C alpha 1 and C alpha 2 germ-line and mature mRNA transcripts in human peripheral blood B cells.
In this study, we investigated the regulation of germ-line and mature C alpha mRNA transcript expression in human peripheral blood B cells. In initial studies, we found that C alpha germ-line and mature transcripts were constitutively expressed in total peripheral blood B cells but not in high density surface IgM+ (surface IgA-) B cells; the latter cells were therefore used in subsequent studies. Focusing first on regulation of germ-line (I alpha-C alpha) transcripts, we showed that C alpha 1 germ-line transcripts are induced by TGF-beta 1 alone but such induction is enhanced by Staphylococcus aureus, Cowan I (SAC). In contrast, C alpha 2 germ-line transcripts are optimally induced by TGF-beta 1 in the absence of a B cell stimulus. In addition, although SAC alone induced both C alpha 1 and C alpha 2 germ-line transcripts, such induction is dependent on endogenous (B cell-derived) TGF-beta 1 production, because no induction is detected in cells cultured in the presence of neutralizing anti-TGF-beta 1. Turning next to mature (VDJ-C alpha) transcripts we showed that SAC plus TGF-beta 1 induces mature C alpha 1 transcripts, and such induction is IL-10 dependent because it is enhanced by exogenous IL-10 and abrogated by the presence of anti-IL-10. In contrast, SAC plus TGF-beta 1 does not induce C alpha 2 mature transcripts, even in the presence of exogenous IL-10; such transcripts are induced, however, by T cell stimuli such as anti-CD40 (presented by CDw32-transfected L cells) in the presence of TGF-beta 1/IL-10 or by PWM-activated T cells. In summary, these studies show that C alpha 1 and C alpha 2 germ-line transcript induction is differentially regulated, in keeping with previous studies of differences in germ-line CH transcript induction in the first and second IgH duplication units. Furthermore, C alpha 1 and C alpha 2 mature transcript induction is also differentially regulated, with C alpha 2 requiring a T cell signal such as that delivered by the CD40 ligand. Finally, IL-10 appears to be uniquely supportive of the induction of both C alpha 1 and C alpha 2 mature transcripts.
Kitani
A
A
Mucosal Immunity Section, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892.
Strober
W
W
D001402:B-Lymphocytes / Q000502:physiology*; D001483:Base Sequence; D017931:DNA Primers / Q000737:chemistry; D005786:Gene Expression Regulation; D015332:Gene Rearrangement, alpha-Chain T-Cell Antigen Receptor; D005803:Genes, Immunoglobulin; D005812:Genes, Switch; D006801:Humans; D007137:Immunoglobulin alpha-Chains / Q000235:genetics*; D016753:Interleukin-10 / Q000494:pharmacology; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000494:pharmacology
D017931:DNA Primers; D007137:Immunoglobulin alpha-Chains; D012333:RNA, Messenger; D011947:Receptors, Antigen, B-Cell; D016212:Transforming Growth Factor beta; D016753:Interleukin-10