In this study, we asked whether exposure to different physiologically relevant temperatures (33°C, 37°C, and 39.5°C) could affect subsequent antigen-specific, activation-related events of naive CD8(+) T cells. We observed that temporary exposure of CD62L(hi)CD44(lo) Pmel-1 CD8(+) cells to 39.5°C prior to their antigen-dependent activation with gp100(25-33) peptide-pulsed C57BL/6 splenocytes resulted in a greater percentage of cells, which eventually differentiated into CD62L(lo)CD44(hi) effector cells compared with cells incubated at 33°C and 37°C. However, the proliferation rate of naive CD8(+) T cells was not affected by mild heating. While exploring these effects further, we observed that mild heating of CD8(+) T cells resulted in the reversible clustering of GM1(+) CD-microdomains in the plasma membrane. This could be attributable to a decrease in line tension in the plasma membrane, as we also observed an increase in membrane fluidity at higher temperatures. Importantly, this same clustering phenomenon was observed in CD8(+) T cells isolated from spleen, LNs, and peripheral blood following mild whole-body heating of mice. Further, we observed that mild heating also resulted in the clustering of TCRβ and the CD8 coreceptor but not CD71R. Finally, we observed an enhanced rate of antigen-specific conjugate formation with APCs following mild heating, which could account for the difference in the extent of differentiation. Overall, these novel findings may help us to further understand the impact of physiologically relevant temperature shifts on the regulation of antigen-specific CD8(+) T cell activation and the subsequent generation of effector cells.

Natural killer cells (NK cells) are the first line of the innate immune defense system, primarily located in peripheral circulation and lymphoid tissues. They kill virally infected and malignant cells through a balancing play of inhibitory and stimulatory receptors. In pre-clinical investigational studies, NK cells show promising anti-tumor effects and are used in adoptive transfer of activated and expanded cells, ex-vivo. NK cells express co-stimulatory molecules that are attractive targets for the immunotherapy of cancers. Recent clinical trials are investigating the use of CAR-NK for different cancers to determine the efficiency. Herein, we review NK cell therapy approaches (NK cell preparation from tissue sources, ways of expansion ex-vivo for “off-the-shelf” allogeneic cell-doses for therapies, and how different vector delivery systems are used to engineer NK cells with CARs) for cancer immunotherapy.

There is increasing documentation of significant survival benefits achieved in cancer patients treated with hyperthermia in combination with radiation and/or chemotherapy. Most evidence collected regarding the mechanisms by which hyperthermia positively influences tumor control has centered on in vitro data showing the ability of heat shock temperatures (usually above 42 degrees C) to result in radio- or chemosensitization. However, these high temperatures are difficult to achieve in vivo, and new thermometry data in patients reveal that much of the tumor and surrounding region is only heated to 40-41 degrees C or less as a result of vascular drainage from the target zone of the heated tumor. Thus, there is now a growing appreciation of a role for mild hyperthermia in the stimulation of various arms of the immune system in contributing to long term protection from tumor growth. Indeed, a review of recent literature suggests the existence of an array of thermally sensitive functions which may exist naturally to help the organism to establish a new "set point" of immune responsiveness during fever. This review summarizes recent literature identifying complex effects of temperature on immune cells and potential cellular mechanisms by which increased temperature may enhance immune surveillance.

SUMMARY T cells compete with malignant cells for limited nutrients within the solid tumor microenvironment. We found that effector memory CD4 T cells respond distinctly from other T cell subsets to limiting glucose and can maintain high levels of interferon-γ (IFN-γ) production in a nutrient-poor environment. Unlike naive (TN) or central memory T (TCM) cells, effector memory T (TEM) cells fail to upregulate fatty acid synthesis, oxidative phosphorylation, and reductive glutaminolysis in limiting glucose. Interference of fatty acid synthesis in naive T cells dramatically upregulates IFN-γ, while increasing exogenous lipids in media inhibits production of IFN-γ by all subsets, suggesting that relative ratio of fatty acid metabolism to glycolysis is a direct predictor of T cell effector activity. Together, these data suggest that effector memory T cells are programmed to have limited ability to synthesize and metabolize fatty acids, which allows them to maintain T cell function in nutrient-depleted microenvironments.

Abbreviations: APC, antigen-presenting cell; CD28, cluster of differentiation 28; CD3, cluster of differentiation 3; CD4, cluster of differentiation 4; CD8, cluster of differentiation 8; CTLA-4, cytotoxic T-lymphocyte-associated protein 4; CTxB, cholera toxin B subunit; Ct, cycle threshold; ELISA, enzyme-linked immunosorbant assay; EtOH, ethanol; FITC, fluoroisothiocyanate; GM1, monosialotetrahexosylganglioside; IDEAS, imagestream data exploration and analysis software; IL-2, interleukin 2; LA, latrunculin A;MbCD, methyl-b-cyclodextrin; PD-1, Programmed cell death-1; PMA, phorbol 12-myristate 13-acetate; pMHC, peptide-major histocompatibility complexes; qRT-PCR, quantitative reverse transcription polymerase chain reaction; TCR, T cell receptor; TDI, time delay integration; TMA-DPH, trimethylammonium diphenylhexatriene; WBH, whole body hyperthermia.Maintenance of normal core body temperature is vigorously defended by long conserved, neurovascular homeostatic mechanisms that assist in heat dissipation during prolonged, heat generating exercise or exposure to warm environments. Moreover, during febrile episodes, body temperature can be significantly elevated for at least several hours at a time. Thus, as blood cells circulate throughout the body, physiologically relevant variations in surrounding tissue temperature can occur; moreover, shifts in core temperature occur during daily circadian cycles. This study has addressed the fundamental question of whether the threshold of stimulation needed to activate lymphocytes is influenced by temperature increases associated with physiologically relevant increases in temperature. We report that the need for co-stimulation of CD4C T cells via CD28 ligation for the production of IL-2 is significantly reduced when cells are exposed to fever-range temperature. Moreover, even in the presence of sufficient CD28 ligation, provision of extra heat further increases IL-2 production. Additional in vivo and in vitro data (using both thermal and chemical modulation of membrane fluidity) support the hypothesis that the mechanism by which temperature modulates co-stimulation is linked to increases in membrane fluidity and membrane macromolecular clustering in the plasma membrane. Thermally-regulated changes in plasma membrane organization in response to physiological increases in temperature may assist in the geographical control of lymphocyte activation, i.e., stimulating activation in lymph nodes rather than in cooler surface regions, and further, may temporarily and reversibly enable CD4C T cells to become more quickly and easily activated during times of infection during fever.