Monocyte:T-cell interaction regulates human T-cell activation through a CD28/CD46 crosstalk.

T-cell activation requires engagement of the T-cell receptor and of at least one costimulatory molecule. The key role of CD28 in inducing T-cell activation was reported several decades ago and the molecular mechanisms involved have now been well described. The complement regulator CD46 also acts as a costimulatory molecule for T cells but, in contrast to CD28, has the ability to drive T-cell differentiation from producing some IFNγ to secreting some potent anti-inflammatory IL-10, acquiring a so-called Type I regulatory phenotype (Tr1).