Lymphoid-enhancing factor functions

LEFl lymphoid enhancer-binding factor lisa 48-kDa nuclear protein expressed in pre-B and T cells. LEFl binds to a functionally important site in the T-cell receptor-alpha enhancer and confers maximal enhancer activity. LEFl belongs to a family of regulatory proteins that share homology with high mobility group protein-1. 

Thus, the bulk of evidence available to date would suggest at least in mice that the spleen contains a population of thymic hormone-responsive lymphoid cells that functions mainly in the suppression of immune responses, perhaps masking concomitant helper effects. In the thymus, the predominant effects of thymic peptides appear to be the induction of functional helper cells, possibly by the enhancement of lymphokine production. The effects of thymulin, thymosin, or other thymic factors on IL-2 production may indeed represent a major function of the endocrine thymus, since IL-2 has been shown to be a potent physiological promoter of T cell maturation (Ruscetti and Gallo, 1981). 

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