CD4 + Th cells play a key role in orchestrating immune responses, but the identity of the CD4 + Th cells involved in the antitumor immune response remains to be defined. We analyzed the immune cell infiltrates of head and neck squamous cell carcinoma and colorectal cancers and identified a subset of CD4 + Th cells distinct from FOXP3 + Tregs that coexpressed programmed cell death 1 (PD-1) and ICOS. These tumor-infiltrating lymphocyte CD4 + Th cells (CD4 + Th TILs) had a tissue-resident memory phenotype, were present in MHC class II–rich areas, and proliferated in the tumor, suggesting local antigen recognition. The T cell receptor repertoire of the PD-1 + ICOS + CD4 + Th TILs was oligoclonal, with T cell clones expanded in the tumor, but present at low frequencies in the periphery. Finally, these PD-1 + ICOS + CD4 + Th TILs were shown to recognize both tumor-associated antigens and tumor-specific neoantigens. Our findings provide an approach for isolating tumor-reactive CD4 + Th TILs directly ex vivo that will help define their role in the antitumor immune response and potentially improve future adoptive T cell therapy approaches.

Mutations in nucleotide-binding oligomerization domain-containing protein 2 (NOD2) cause Blau syndrome, an inflammatory disorder characterized by uveitis. The antimicrobial functions of Nod2 are well-established, yet the cellular mechanisms by which dysregulated Nod2 causes uveitis remain unknown. Here, we report a non-conventional, T cell-intrinsic function for Nod2 in suppression of Th17 immunity and experimental uveitis. Reconstitution of lymphopenic hosts with Nod2−/− CD4+ T cells or retina-specific autoreactive CD4+ T cells lacking Nod2 reveals a T cell-autonomous, Rip2-independent mechanism for Nod2 in uveitis. In naive animals, Nod2 operates downstream of TCR ligation to suppress activation of memory CD4+ T cells that associate with an autoreactive-like profile involving IL-17 and Ccr7. Interestingly, CD4+ T cells from two Blau syndrome patients show elevated IL-17 and increased CCR7. Our data define Nod2 as a T cell-intrinsic rheostat of Th17 immunity, and open new avenues for T cell-based therapies for Nod2-associated disorders such as Blau syndrome.

Arthritis in a genetically susceptible SKG strain of mice models a theoretical paradigm wherein autoimmune arthritis arises because of interplay between preexisting autoreactive T cells and environmental stimuli. SKG mice have a point mutation in ZAP-70 that results in attenuated TCR signaling, altered thymic selection, and spontaneous production of autoreactive T cells that cause arthritis following exposure to microbial β-glucans. In this study, we identify Nod2, an innate immune receptor, as a critical suppressor of arthritis in SKG mice. SKG mice deficient in Nod2 (Nod2SKG) developed a dramatically exacerbated form of arthritis, which was independent of sex and microbiota, but required the mutation in T cells. Worsened arthritis in Nod2SKG mice was accompanied by expansion of Th17 cells, which to some measure coproduced TNF, GM-CSF, and IL-22, along with elevated IL-17A levels within joint synovial fluid. Importantly, neutralization of IL-17A mitigated arthritis in Nod2SKG mice, indicating that Nod2-mediated protection occurs through suppression of the Th17 response. Nod2 deficiency did not alter regulatory T cell development or function. Instead, Nod2 deficiency resulted in an enhanced fundamental ability of SKG CD4 T cells (from naive mice) to produce increased levels of IL-17 and to passively transfer arthritis to lymphopenic recipients on a single-cell level. These data reveal a previously unconsidered role for T cell-intrinsic Nod2 as an endogenous negative regulator of Th17 responses and arthritogenic T cells. Based on our findings, future studies aimed at understanding a negative regulatory function of Nod2 within autoreactive T cells could provide novel therapeutic strategies for treatment of patients with arthritis.

Microsatellite-stable (MSS) colorectal cancers are characterized by low mutation burden and limited immune-cell infiltration and thereby respond poorly to immunotherapy. Here, we report a case of metastatic MSS colorectal cancer with a robust anticancer immune response. The primary tumor was resected in 2012, and the patient received several cycles of chemotherapy until 2017. In 2018, the patient underwent a left hepatectomy to remove a new metastasis. Analysis of the metastatic tumor revealed a strong CD8+ T-cell response. A high frequency of CD8+ T cells coexpressed CD39 and CD103, a phenotype characteristic of tumor-reactive cells. Using whole-exome sequencing, we identified somatic mutations that generated peptides recognized by CD39+CD103+CD8+ T cells. The observed reactivity against the tumor was dominated by the response to a single mutation that emerged in the metastasis. Somatic mutations that were not immunogenic in the primary tumor led to robust CD8+ T-cell expansion later during disease progression. Our data suggest that the cytotoxic treatment regimen received by the patient might be responsible for this effect. Hence, the capacity of cytotoxic regimens to prime the immune system in colorectal cancer patients should be investigated further and might provide a rationale for combination with immunotherapy.