The LTi cell, an immunologic chameleon

Abstract

Lymphoid tissue inducer (LTi) cells are key components of the machinery required for the construction of the lymphoid structures underlying immune responses. In this issue of Immunity, Vonarbourg et. al. (2010) describe how these cells assume several different guises, each associated with different LTi functions.

Figure 1. Changes in Intenstinal LTi Populations during Maturation

In the fetal gut, the LTα₁β₁⁺ LTi cell is an RORγt⁺ cell that does not yet express NKp46; this cell is potentially capable of producing IL-17 and IL-22 but may not do so because of low IL-23 concentration at this stage. In the neonatal gut lumenal microbiota are present and the LTi cell now expresses NKp46 and becomes an NKR-LTi cell; this cell produces mainly IL-22 in response to IL-23. Finally, in the postnatal period, LTi cells lose RORγt expression and become an LTi-derived NK cells; these cells can produce IFN-γ in response to IL-23 stimulation. Although this diagram describes the progression of LTi changes over time, in reality, these various cells may coexist in the postnatal gut.