Lymphotoxin-beta receptor activation on macrophages ameliorates acute DSS-induced intestinal inflammation in a TRIM30α-dependent manner.

Our previous studies indicated that LTβR activation mainly by T cell derived LTα₁β₂ is crucial for the control and down-regulation of intestinal inflammation. In order to dissect the cellular and molecular role of LTβR activation in the experimental model of DSS-induced intestinal inflammation, we have generated cell type-specific LTβR-deficient mice with specific ablation of LTβR expression on macrophages/neutrophils (LTβR((flox/flox))×LysM-Cre). These mice develop an exacerbated intestinal inflammation in our experimental model indicating that LTβR expression on macrophages/neutrophils is responsible for the control and down-regulation of the inflammatory reaction. These results were verified by adoptive transfer experiments of BMDM from wild-type and LTβR-deficient mice. Furthermore, transfer of activated CD4+ T cells derived from wild-type mice, but not from LTβR ligand-deficient mice attenuated the signs of intestinal inflammation. Finally, we demonstrate that LTβR activation on BMDM results in induction of TRIM30α, a negative regulator of NFκB activation. Concordantly, ablation of LTβR signaling results in the inability to induce TRIM30α expression concomitant with an increased expression of pro-inflammatory cytokines in our experimental model. Taken together, our data demonstrate that LTβR activation on macrophages by CD4+ T cell derived LTαβ controls the pro-inflammatory response by activation of a TRIM30α-dependent signaling pathway, crucial for the down-regulation of the inflammatory response in this experimental model.