Interleukin-12-responding asialoGM1+CD8+ central memory-type T cells as precursor cells for interferon-gamma-producing killer T cells

Senescent CD8+ T cells acquire NK cell-like innate functions to promote antitumor immunity

It has been suggested that aging of the immune system (immunosenescence) results in a decline in the acquired immune response, which is associated with an increase in age-related tumorigenesis. T-cell senescence plays a critical role in immunosenescence and is involved in the age-related decline of the immune function, which increases susceptibility to certain cancers. However, it has been shown that CD8⁺ T cells with the senescent T-cell phenotype acquire an natural killer (NK) cell-like function and are involved in tumor elimination. Therefore, the role of senescent CD8⁺ T cells in tumor immunity remains to be elucidated. In this study, we investigated the role of senescent CD8⁺ T cells in tumor immunity. In a murine model of transferred with B16 melanoma, lung metastasis was significantly suppressed in aged mice (age ≥30 weeks) in comparison to young mice (age 6-10 weeks). We evaluated the cytotoxic activity of CD8⁺ T cells in vitro and found that CD8⁺ T cells from aged mice activated in vitro exhibited increased cytotoxic activity in comparison to those from young mice. We used Menin-deficient effector T cells as a model for senescent CD8⁺ T cells and found that cytotoxic activity and the expression of NK receptors were upregulated in Menin-deficient senescent CD8⁺ T cells. Furthermore, Menin-deficient CD8⁺ T cells can eliminate tumor cells in an antigen-independent manner. These results suggest that senescent effector CD8⁺ T cells may contribute to tumor immunity in the elderly by acquiring NK-like innate immune functions, such as antigen-independent cytotoxic activity.

In vivo regulation of experimental autoimmune encephalomyelitis by NK cells: alteration of primary adaptive responses

Innate immune responses provide the host with its first line of defense against infections. Signals generated by subsets of lymphocytes, including NK cells, NKT cells, and APC during this early host response determine the nature of downstream adaptive immune responses. In the present study, we have examined the role of innate NK cells in an autoimmune model through the use of primary immunization with the myelin oligodendrocyte glycoprotein peptide to induce experimental autoimmune encephalomyelitis (EAE). Our studies have shown that in vivo depletion of NK cells can affect the adaptive immune responses, because NK cells were found to regulate the degree of clinical paralysis and to alter immune adaptive responses to the myelin oligodendrocyte glycoprotein peptide. The requirement for NK cells was reflected by changes in the T cell responses and diminished clinical disease seen in mice treated with anti-NK1.1, anti-asialo GM1, and selected Ly49 subtype-depleted mice. In addition to alteration in T cell responses, the maturational status of dendritic cells in lymph nodes was altered both quantitatively and qualitatively. Finally, examination of TCR Vbeta usage of the brain lymphocytes from EAE mice indicated a spectra-type change in receptor expression in NK- depleted mice as compared with non-NK-depleted EAE mice. These findings further establish a recently postulated link between NK cells and the generation of autoreactive T cells.

CC-chemokine ligand 17 gene therapy induces tumor regression through augmentation of tumor-infiltrating immune cells in a murine model of preexisting CT26 colon carcinoma

Chemokines, which regulate leukocyte trafficking and infiltration of local sites, are attractive candidates for improving the efficacy of cancer immunotherapy by enhancing the accumulation of immune cells in tumor tissue. Herein, we evaluated the antitumor effects of intratumoral injection of RGD fiber-mutant adenoviral vectors (AdRGDs) encoding the chemokines CCL17, CCL19, CCL20, CCL21, CCL22, CCL27, XCL1 or CX3CL1 in a murine model of preexisting CT26 colon carcinoma. Among these 8 chemokine-expressing AdRGDs, injection of AdRGD-CCL17 most effectively induced tumor regression and generated specific immunity in rechallenge experiments. Tumor elimination activity by intratumoral injection of AdRGD-CCL17 depended on both the vector dose and the number of injections, and mainly required CD8+ CTLs in an effector phase as confirmed by analysis using BALB/c nude mice and an in vivo depletion assay. In addition, CCL17 gene transduction induced significant increases in the number of infiltrating macrophages and CD8+ T cells in CT26 tumors, and changed the tumor microenvironment to an immunologic activation state in which there was enhanced expression of lymphocyte activation markers and cell adhesion molecules. Thus, our data provide evidence that CCL17 gene transduction of local tumor sites is a promising approach for the development of a cancer immunogene therapy that can recruit activated tumor-infiltrating immune effector cells.