Single naive CD4+ T cells from a diverse repertoire produce different effector cell types during infection.

ABSTRACT

A naive CD4(+) T cell population specific for a microbial peptidemajor histocompatibility complex II ligand (pMHCII) typically consists of about 100 cells, each with a different T cell receptor (TCR). Following infection, this population produces a consistent ratio of effector cells that activate microbicidal functions of macrophages or help B cells make antibodies. We studied the mechanism that underlies this division of labor by tracking the progeny of single naive T cells. Different naive cells produced distinct ratios of macrophage and B cell helpers but yielded the characteristic ratio when averaged together. The effector cell pattern produced by a given naive cell correlated with the TCR-pMHCII dwell time or the amount of pMHCII. Thus, the consistent production of effector cell subsets by a polyclonal population of naive cells results from averaging the diverse behaviors of individual clones, which are instructed in part by the strength of TCR signaling.