Peripheral residence of naïve CD4 T cells induces MHC class II-dependent alterations in phenotype and function

Background As individual naive CD4 T lymphocytes circulate in the body after emerging from the thymus, they are likely to have individually varying microenvironmental interactions even in the absence of stimulation via specific target recognition. It is not clear if these interactions result in alterations in their activation, survival and effector programming. Naive CD4 T cells show unimodal distribution for many phenotypic properties, suggesting that the variation is caused by intrinsic stochasticity, although underlying variation due to subsets created by different histories of microenvironmental interactions remains possible. To explore this possibility, we began examining the phenotype and functionality of naive CD4 T cells differing in a basic unimodally distributed property, the CD4 levels, as well as the causal origin of these differences.