A single population of tolerogenic APC induce two types of CD4+ Treg cells by two different mechanisms. (P1054)

Abstract

Abstract Anterior chamber associated immune deviation,ACAID, is an animal model developed to study immune privileged mechanisms of the eye. The in vitro correlate of ACAID is traditionally used to study the cellular and molecular mechanism of the Treg cell development. Tolerogenic antigen-presenting cells (TolAPC) are required to express F4/80 for induction of efferent CD8+ Treg cells. We wondered if F480 is required for the development of afferent CD4+ Treg cells subpopulations. CD4+ Treg cells from cultures containing F4/80 deficient TolAPC cells partially inhibited an in vivo proliferative response to antigen. The depletion of CD25+ T cells after (but not before) exposure to TolAPC in vitro removed all inhibitory activity of the T cells in vivo. Thus, CD4+CD25+ Treg cells generated in vitro are not dependent on F4/80 but do require PDL-1 expression by the TolAPC . Since the F4/80 dependent CD4+ CD25- Treg cells express LAP-1 and PD-1, but not FoxP3, and the F4/80 independent CD4+ CD25+ Treg cells express FoxP3, PD-1, PD-L1, but not LAP-1, they resemble the mucosally-defined Th3 and inducible (i)Treg cells, respectively. Flow cytometry analyses showed that rather than two subpopulations of TolAPC, a single population of F4/80+PD-L1+TolAPC was generated by TGFβ and antigen pretreatment. Together, these data suggest that two subpopulations of afferent CD4+ Treg cells are induced by a single population of TolAPC in vitro.