Functional Heterogeneity of CD4 Tumor-Infiltrating Lymphocytes With a Resident Memory Phenotype in NSCLC.

Resident memory T cells (T) inhabit peripheral tissues and are critical for protection against localized infections. Recently, it has become evident that CD103 T are not only important in combating secondary infections, but also for the elimination of tumor cells. In several solid cancers, intratumoral CD103CD8 tumor infiltrating lymphocytes (TILs), with T properties, are a positive prognostic marker. To better understand the role of T in tumors, we performed a detailed characterization of CD8 and CD4 TIL phenotype and functional properties in non-small cell lung cancer (NSCLC). Frequencies of CD8 and CD4 T cell infiltrates in tumors were comparable, but we observed a sharp contrast in T ratios compared to surrounding lung tissue. The majority of both CD4 and CD8 TILs expressed CD69 and a subset also expressed CD103, both hallmarks of T. While CD103CD8 T cells were enriched in tumors, CD103CD4 T cell frequencies were decreased compared to surrounding lung tissue. Furthermore, CD103CD4 and CD103CD8 TILs showed multiple characteristics of T, such as elevated expression of CXCR6 and CD49a, and decreased expression of T-bet and Eomes. In line with the immunomodulatory role of the tumor microenvironment, CD8 and CD4 TILs expressed high levels of inhibitory receptors 2B4, CTLA-4, and PD-1, with the highest levels found on CD103 TILs. Strikingly, CD103CD4 TILs were the most potent producers of TNF-α and IFN-γ, while other TIL subsets lacked such cytokine production. Whereas, CD103CD4PD-1 TILs produced the most effector cytokines, CD103CD4PD-1 and CD69CD4PD-1 TILs produced CXCL13. Furthermore, a large proportion of TILs expressed co-stimulatory receptors CD27 and CD28, unlike lung T, suggesting a less differentiated phenotype. Agonistic triggering of these receptors improved cytokine production of CD103CD4 and CD69CD8 TILs. Our findings thus provide a rationale to target CD103CD4 TILs and add co-stimulation to current therapies to improve the efficacy of immunotherapies and cancer vaccines.