Localization-associated immune phenotypes of clonally expanded tumor-infiltrating T cells and distribution of their target antigens in rectal cancer

The degree and type of T cell infiltration influence rectal cancer prognosis regardless of classical tumor staging. We asked whether clonal expansion and tumor infiltration are restricted to selected-phenotype T cells; which clones are accessible in peripheral blood; and what the spatial distribution of their target antigens is. From five rectal cancer patients, we isolated paired tumor-infiltrating T cells (TILs) and T cells from unaffected rectum mucosa (T(UM)) using 13-parameter FACS single cell index sorting. TCRαβ sequences, cytokine, and transcription factor expression were determined with single cell sequencing. TILs and T(UM) occupied distinct phenotype compartments and clonal expansion predominantly occurred within CD8(+) T cells. Expanded TIL clones identified by paired TCRαβ sequencing and exclusively detectable in the tumor showed characteristic PD-1 and TIM-3 expression. TCRβ repertoire sequencing identified 49 out of 149 expanded TIL clones circulating in peripheral blood and 41 (84%) of these were PD-1(-) TIM-3(-). To determine whether clonal expansion of predominantly tumor-infiltrating T cell clones was driven by antigens uniquely presented in tumor tissue, selected TCRs were reconstructed and incubated with cells isolated from corresponding tumor or unaffected mucosa. The majority of clones exclusively detected in the tumor recognized antigen at both sites. In summary, rectal cancer is infiltrated with expanded distinct-phenotype T cell clones that either i) predominantly infiltrate the tumor, ii) predominantly infiltrate the unaffected mucosa, or iii) overlap between tumor, unaffected mucosa, and peripheral blood. However, the target antigens of predominantly tumor-infiltrating TIL clones do not appear to be restricted to tumor tissue

Type 2 T cell responses against distinct epitopes of the desmoglein 3 ectodomain in pemphigus vulgaris.

Pemphigus vulgaris (PV) is an autoimmune blistering disorder of the skin and/or mucous membranes caused by IgG autoantibodies which predominantly target two transmembrane desmosomal cadherins, desmoglein (Dsg)1 and Dsg3. Dsg-specific T cells play a central role in PV pathogenesis as they provide help to autoreactive B cells for autoantibody production. We here characterized Dsg3-specific peripheral T cells in a cohort of 52 PV patients and 41 healthy controls (HC) with regard to cytokine profile and epitope specificity. By ELISpot analysis, type 2 T cells reactive with the Dsg3 ectodomain were significantly increased in PV patients compared to HC. By dextramer analysis, CD4+ T cells specific for an epitope within the extracellular domain of Dsg3, Dsg3(206-220), were found at significantly higher frequencies in PV patients than in HLA-matched HC. T cell recognition of two distinct Dsg3 epitopes, i.e. Dsg3(206-220) and Dsg3(378-392), correlated significantly suggesting a synergistic effect in B cell help. Immunization of HLA-DRB1*04:02-transgenic PV mice with the same set of Dsg3 peptides induced pathogenic Dsg3-specific IgG antibodies which induced loss of keratinocyte adhesion in vitro. Thus, Dsg3 peptide-specific T cells are of particular interest as surrogate marker of disease activity and potential therapeutic targets in PV