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Vitamin A regulates proliferation and apoptosis of human T- and B-cells.

Blomhoff HK

Department of Biochemistry, Institute of Basic Medical Sciences, University of Oslo, P.O. Box 1112, Blindern, N-0317 Oslo, Norway. h.k.blomhoff@basalmed.uio.no

Vitamin A is known to protect against infections, but it is not established how vitamin A metabolites stimulate the immune system. We have investigated the effects of physiological levels of retinoic acid on the function of normal human T- and B-cells. Surprisingly, we found that the proliferation of B-cells was inhibited by retinoids, and that this was due to rapid inhibition of the cell cycle machinery regulating G(1)-to-S transition. In contrast, the proliferation of T-cells was enhanced by physiological levels of retinoic acid, and the effect was due to induction of IL-2 (interleukin 2). The 'non-death-receptor'-mediated apoptosis of normal T-cells induced by prolonged (but single) stimulation of the cells was also prevented by retinoid acid, and also this effect was mediated via enhanced production of IL-2. The induction of IL-2 was at the transcriptional level, and all the effects of vitamin A on both B-and T-cells were mediated via the nuclear retinoic acid receptors (RARs), and not retinoid X receptors (RXRs).

Published 27 October 2004 in Biochem Soc Trans, 32: 982-4.
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