CD1d-restricted help to B cells by human invariant natural killer T lymphocytes

Grazia Galli, Sandra Nuti, Simona Tavarini, Luisa Galli-Stampino, Claudia De Lalla, Giulia Casorati, Paolo Dellabona, Sergio Abrignani

Research output: Contribution to journalArticlepeer-review


Invariant natural killer T (NKT) cells are a highly conserved subset of T lymphocytes expressing a semi-invariant T cell receptor (TCR), which is restricted to CDld and specific for the glycosphingolipid antigen α-galactosylceramide. Their ability to secrete a variety of cytokines, which in turn modulate the activation of cells of both innate and acquired immune responses, suggests that invariant NKT cells exert a regulatory role mainly via indirect mechanisms. A relevant question is whether invariant NKT cells can directly help B cells. We document here that human invariant NKT cells are as efficient as conventional CD4+ Th0 lymphocytes in promoting proliferation of autologous memory and naive B lymphocytes in vitro, and in inducing immunoglobulin production. Help to B cells by invariant NKT cells is CD1d-dependent and delivered also in the absence of α-galactosylceramide, suggesting that NKT cells recognize an endogenous ligand presented by CD1d on B cells. The two major subsets of invariant NKT cells, CD4+ and double negative (CD4-CD8-), express comparable levels of CD40 ligand and cytokines, but differ in helper functions. Indeed, both subsets induce similar levels of B cell proliferation, whereas CD4+ NKT cells induce higher levels of immunoglobulin production. These results suggest a direct role for invariant NKT cells in regulating B lymphocyte proliferation and effector functions.

Original languageEnglish
Pages (from-to)1051-1057
Number of pages7
JournalJournal of Experimental Medicine
Issue number8
Publication statusPublished - Apr 21 2003


  • α-galactosylceramide
  • Antibodies
  • Autoreactivity
  • Cytokine
  • Helper assay

ASJC Scopus subject areas

  • Immunology


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