Tuesday 17 February, 2009 from 12.00 to 13.00
Fabienne ANDRIS

" Role of interleukine-6 in the regulation of humoral and Th2 responses"

The conditions leading to the activation / differentiation of T helper

(Th) cells dedicated for B cell antibody production are still poorly characterized. We now demonstrate that interleukin (IL)-6 promotes the differentiation of naïve T lymphocytes into helper cells able to promote B cell activation and antibody secretion. IL-6 driven- acquisition of B cell help capacity requires expression of the STAT3, but not STAT4 or

STAT6 transcription factors, suggesting that the ability to provide help to B cells is not restricted to a well-defined Th1 or Th2 effector population. T-cell specific STAT3-deficient mice displayed reduced humoral responses in vivo that could not be related to an altered expansion of CXCR5-expressing helper T cells. IL-6 was shown to promote

IL-21 secretion, a cytokine that was similarly found to promote the differentiation of naïve T cells into potent B cell helper cells.

Collectively these data indicate that the ability to provide B cell help is regulated by IL-6 / IL-21 through STAT3 activation, independently of Th1, Th2, Th17 or T_FH differentiation.