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Follicular helper NKT cells induce limited B cell responses and germinal center formation in the absence of CD4(+) T cell help.


ABSTRACT: B cells require MHC class II (MHC II)-restricted cognate help and CD40 engagement by CD4(+) T follicular helper (T(FH)) cells to form germinal centers and long-lasting Ab responses. Invariant NKT (iNKT) cells are innate-like lymphocytes that jumpstart the adaptive immune response when activated by the CD1d-restricted lipid ?-galactosylceramide (?GalCer). We previously observed that immunization of mice lacking CD4(+) T cells (MHC II(-/-)) elicits specific IgG responses only when protein Ags are mixed with ?GalCer. In this study, we investigated the mechanisms underpinning this observation. We find that induction of Ag-specific Ab responses in MHC II(-/-) mice upon immunization with protein Ags mixed with ?GalCer requires CD1d expression and CD40 engagement on B cells, suggesting that iNKT cells provide CD1d-restricted cognate help for B cells. Remarkably, splenic iNKT cells from immunized MHC II(-/-) mice display a typical CXCR5(hi)programmed death-1(hi)ICOS(hi)Bcl-6(hi) T(FH) phenotype and induce germinal centers. The specific IgG response induced in MHC II(-/-) mice has shorter duration than that developing in CD4-competent animals, suggesting that iNKT(FH) cells preferentially induce transient rather than long-lived Ab responses. Together, these results suggest that iNKT cells can be co-opted into the follicular helper function, yet iNKT(FH) and CD4(+) T(FH) cells display distinct helper features, consistent with the notion that these two cell subsets play nonredundant functions throughout immune responses.

SUBMITTER: Tonti E 

PROVIDER: S-EPMC3559029 | biostudies-literature | 2012 Apr

REPOSITORIES: biostudies-literature

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Follicular helper NKT cells induce limited B cell responses and germinal center formation in the absence of CD4(+) T cell help.

Tonti Elena E   Fedeli Maya M   Napolitano Anna A   Iannacone Matteo M   von Andrian Ulrich H UH   Guidotti Luca G LG   Abrignani Sergio S   Casorati Giulia G   Dellabona Paolo P  

Journal of immunology (Baltimore, Md. : 1950) 20120229 7


B cells require MHC class II (MHC II)-restricted cognate help and CD40 engagement by CD4(+) T follicular helper (T(FH)) cells to form germinal centers and long-lasting Ab responses. Invariant NKT (iNKT) cells are innate-like lymphocytes that jumpstart the adaptive immune response when activated by the CD1d-restricted lipid α-galactosylceramide (αGalCer). We previously observed that immunization of mice lacking CD4(+) T cells (MHC II(-/-)) elicits specific IgG responses only when protein Ags are  ...[more]

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