Renal tubular epithelial cells are constitutive non-cognate stimulators of resident T cells.

Understanding the roles of different cell types in regulating T cell homeostasis in various tissues is critical for understanding adaptive immunity. Here, we show that RTECs (renal tubular epithelial cells) are intrinsically programmed to polyclonally stimulate proliferation of kidney αβ T cells by a cell-cell contact mechanism that is major histocompatibility complex (MHC) independent and regulated by CD155, αVβ3-integrin, and vitronectin. Peripheral CD4 and CD8 are resistant to RTEC-mediated stimulation, while the minor subset of double-negative (DN) T cells are responsive. This functional property of RTEC is discovered by using a coculture system that recapitulates spontaneous in vivo polyclonal proliferation of kidney T cells, which are mainly comprised of central memory T (T) and effector memory T (T) cells. This robust cell-intrinsic stimulatory role of RTECs could be underlying the steady-state spontaneous proliferation of kidney T cells. The results have conceptual implications for understanding roles of different cell types in regulating systemic and organ-specific T cell homeostasis.