Lymph node stromal cells acquire peptide-MHCII complexes from dendritic cells and induce antigen-specific CD4⁺ T cell tolerance.
Bottom Line: Although LNSCs express MHCII, it is unknown whether they can also impact CD4(+) T cell functions.We show that the promoter IV (pIV) of class II transactivator (CIITA), the master regulator of MHCII expression, controls endogenous MHCII expression by LNSCs.Our data reveals a novel, alternative mechanism where LN-resident stromal cells tolerize CD4(+) T cells through the presentation of self-antigens via transferred peptide-MHCII complexes of DC origin.
Affiliation: Department of Pathology and Immunology, University of Geneva Medical School, 1211 Geneva, Switzerland.Show MeSH
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Mentions: To study the impact of pMHCII transfer from DCs to LNSCs on CD4+ T cells in vivo, we took advantage of the mouse model CD11cDOG (CD11cDTR-OVA-eGFP) in which OVA protein is exclusively expressed by DCs (Hochweller et al., 2008; Fig. 7 A). In contrast to DCs, LNSCs purified from CD11cDOG mice did not express OVA mRNA (Fig. 7 B), excluding the possibility that in this model, LNSCs endogenously express and may directly present OVA to T cells. Next, LNSCs and DCs were sorted from either WT or CD11cDOG mice and incubated for 3 d with CFSE-labeled OT-II CD4+ T cells. As expected, T cells proliferated well after culture with CD11cDOG but not WT DCs (Fig. 7 C). Although we did not observe any significant proliferation when OT-II cells were incubated with WT or CD11cDOG LECs, BECs, or FRCs, Annexin V staining revealed that more T cells became apoptotic when co-cultured with CD11cDOG LECs compared with WT LECs (Fig. 7 C). Thus, consistent with published studies showing that LECs can induce T cell deletion (Lund et al., 2012; Tewalt et al., 2012) and correlating with the higher expression of PD-L1 by LECs compared with other LNSC populations observed (Fig. 7 D), our data suggest that under steady state, LECs acquire pMHCII complexes from DCs and promote CD4+ T cell apoptosis in an antigen-specific manner.
Affiliation: Department of Pathology and Immunology, University of Geneva Medical School, 1211 Geneva, Switzerland.