Characterization of anergic anti-DNA B cells: B cell anergy is a T cell-independent and potentially reversible process

Anti-single stranded DNA (ssDNA) and anti-double stranded DNA (dsDNA) a cel ls are regulated in non-autoimmune mice. In this report we show that while both anti-ssDNA and anti-dsDNA a cells are blocked in their ability to diff erentiate into antibody-secreting cells, other phenotypic and functional ch aracteristics distinguish them from one another. Splenic anti-ssDNA a cells are found distributed throughout the a cell follicle, and are phenotypical ly mature and long-lived. On the other hand, splenic anti-dsDNA B cells are short-lived, exhibit an immature and antigen-experienced phenotype, and lo calize to the T-B interface of the splenic follicle. Functionally, anti-ssD NA a cells proliferate, albeit suboptimally, in response to anti-Igm, lipop olysaccharide (LPS) and CD40L/IL-4 + anti-IgM stimulation, and tyrosine pho sphorylate intracellular proteins upon mIgM cross-linking. Anti-dsDNA a cel ls, on the other hand, are functionally unresponsive to anti-IgM and LPS st imulation, and do not phosphorylate intracellular proteins, including Syk, upon mig stimulation. Importantly, anti-DNA a cell anergy is maintained in the absence of T cells since both anti-ssDNA and anti-dsDNA B cells are as efficiently regulated in RAG2(-/-) mice as in their RAG2(+/+) counterparts. Interestingly, the severely anergic state of anti-dsDNA a cells is partial ly reversible upon stimulation with CD40 ligand and IL-4. In response to th ese signals, anti-dsDNA a cells remain viable, up-regulate cell surface exp ression of B7-2 and IgM, and restore their ability to proliferate and phosp horylate Syk upon mig cross-linking. Collectively, these data suggest that anti-DNA a cell anergy encompasses distinct phenotypes which, even in its m ost severe form, may be reversible upon stimulation with T cell-derived fac tors.