Differential effect of transforming growth factor-{beta}1 on the activation of human naive and memory CD4+ T lymphocytes

Transforming growth factor-ß1 (TGF-ß1) canhave stimulatory or inhibitory effects on cell growth. For severalcell types, the effect of TGF-ß1 was found to correlatewith the differentiation stage of the cells and the presenceof other cytoklnes. We have studied here the influence of TGF-ß1on CD4⁺ T cell activation in relation to the differentiationstage of the cells by evaluating the effect of TGF-ß1on the prollferatlve responses of purified CD4⁺CD45RA⁺ (unprfmed)and CD4⁺CD45RO⁺ (primed) lymphocytes. Under certain conditions,TGF-ß1 exerted a co-stlmulatory effect on peripheralblood CD4⁺CD45RA⁺ T cells whereas the outgrowth of CD4⁺CD45RO⁺T cells was suppressed in any activation system tested. Theenhancement of prollferatlve responses by TGF-ß1 inTCR/CD3 or CD2 stimulated cultures of CD45RA⁺ cells involvedup-regulatlon of CD25 expression and was dependent on the presenceof exogenous IL-2 or CD28 mAbs; IL-7 driven proliferatlve responseswere suppressed by TGF-ß1. These observations wereconfirmed in experiments with purified cord blood (CB) CD4⁺T cells inasmuch as addition of TGF-ß1 caused a 2-to 7-fold increase in IL-2 driven proliferatlve responses ofthese cells. Finally we show that, in contrast to the effectof TGF-ß1 during primary stimulation of CB CD4⁺ Tcells, TGF-ß1 suppressed T cell proliferation for40% in secondary cultures of these cell. Our findings indicatethat TGF-ß1 Is a blfunctlonal regulator of CD4⁺ Tcell growth in vitro, with co-stimulatory capacities duringCD45RA⁺ T cell mediated primary responses and growth suppresslveeffects during secondary responses of CD45RO⁺ T cells.