Distinct lymph node entry efficiencies for CD8+ and CD4+ T cells are eliminated during malnourishment

Previous work suggests that glucocorticoids upregulate expression of CD127, an IL-7 receptor component, on peripheral naïve T cells (NT), even though the total number of peripheral NT declines dramatically during malnourishment. We proposed that CD127 up-regulation contributes to peripheral NT reduction by increasing the scavenge rate of IL-7, providing a mechanism to rapidly adjust the total number of NTs during malnutrition. Each malnourished NT would then receive a larger dose of IL-7 than control NTs. We next wondered if this larger dose might confer additional energy-saving behaviors. NT migration across HEV’s may be a high energy-consuming activity. Thus, we compared lymph node entry rates of adoptively-transferred malnourished and control NT in malnourished and control recipients. Control CD4+ NTs migrated more efficiently than control CD8+ NT, but malnourished CD4+ and CD8+ NT migrated at equivalent rates, regardless of recipient diet. We next analyzed expression of proteins known to be involved in NT migration to uncover the currently unknown mechanisms responsible for these various migration patterns. Flow cytometry analysis revealed malnutrition significantly reduces expression of both components of LFA-1 (CD18 and CD11a), CD49d (a VLA-4 component), and S1PR1 in CD4+ and CD8+ NT. We also compared expression levels of ICAM-1 (CD54), a protein expressed in HEV’s which binds to LFA-1 on migrating NT, in malnourished and control lymph node tissue via confocal microscopy. Improved understanding of altered migration molecule expression during malnourishment should enhance our knowledge of the energy-conserving behavior of NT, as well as uncover strategies to improve vaccination responses in malnourished children.

CD38-NAD+Axis Regulates Immunotherapeutic Anti-Tumor T Cell Response

Heightened effector function and prolonged persistence, the key attributes of Th1 and Th17 cells, respectively, are key features of potent anti-tumor T cells. Here, we established ex vivo culture conditions to generate hybrid Th1/17 cells, which persisted long-term in vivo while maintaining their effector function. Using transcriptomics and metabolic profiling approaches, we showed that the enhanced anti-tumor property of Th1/17 cells was dependent on the increased NAD⁺-dependent activity of the histone deacetylase Sirt1. Pharmacological or genetic inhibition of Sirt1 activity impaired the anti-tumor potential of Th1/17 cells. Importantly, T cells with reduced surface expression of the NADase CD38 exhibited intrinsically higher NAD⁺, enhanced oxidative phosphorylation, higher glutaminolysis, and altered mitochondrial dynamics that vastly improved tumor control. Lastly, blocking CD38 expression improved tumor control even when using Th0 anti-tumor T cells. Thus, strategies targeting the CD38-NAD⁺ axis could increase the efficacy of anti-tumor adoptive T cell therapy.

Defining the mechanisms and cues that influence cytotoxic T cell homeostasis during malnourishment (LYM2P.727)

T cell homeostasis is clearly disrupted by malnutrition, but the precise cues and mechanisms through which it occurs are unknown. Short-term malnutrition reduces the size of the peripheral CD8+ T population in mice. Perhaps paradoxically, malnourished CD8+ T cells are less sensitive to death-by-neglect and express higher levels of CD127, a component of the IL-7 receptor. We aimed to identify whether vitamin and mineral deficiency or reduced caloric intake triggers these changes and to better understand the molecular mechanisms through which such changes occur. While vitamin and mineral deficiency is not sufficient to reduce total CD8+ T cell numbers or trigger CD127 up-regulation, it is sufficient to reduce CD8+ T cell sensitivity to death-by-neglect. Mechanistically, we have determined that the reduced sensitivity to death-by-neglect observed in malnourished CD8+ T cells is Foxo1-dependent. Given that CD127 is a transcriptional target of Foxo1, additional studies were conducted to determine if CD127 is up-regulated or if CD127low CD8+ T cells are simply out-competed in a malnourished environment. Our results suggest that during malnourishment, Foxo1 induces the up-regulation of CD127 on CD8+ T cells, which may relate to the cells’ reduced sensitivity to growth factor withdrawal. While different mechanisms may be triggered by calorie versus vitamin and mineral deficiency, both deficiencies reduce CD8+ T cell sensitivity to death-by-neglect.

The forkhead transcription factor, Foxo1, may coordinate naïve CD8+ T cell homeostasis with energy availability in mice. (LYM4P.758)

The naïve CD8+ T cell population must be large enough so that sufficient diversity exists to respond to potential pathogens, yet not so large as to unnecessarily drain an organism’s resources. Thus, we propose that a molecular network links the size of the naïve CD8+ T cell pool with energy availability. We report that short-term calorie restriction in C57BL/6 mice resulted in reduced numbers of naïve CD8+ T cells which efficiently engaged survival signals and minimized energy usage. For example, calorie restricted naïve CD8+ T expressed higher levels of CD8 and CD127 than ad libitum cells, both of which are responsible for receiving homeostatic survival signals in vivo. Naïve CD8+ T cells isolated from calorie restricted mice also experienced less death-by-neglect and engaged in less glycolysis than cells isolated from mice fed ad libitum. Finally, neither the size of the naïve CD8+ T cell pool nor the sensitivity of those cells to death-by-neglect were affected by calorie restriction in the absence of the forkhead transcription factor, Foxo1, indicating that Foxo1 may be involved in synchronizing the size of the naïve CD8+ T cell pool with energy availability.

The forkhead transcription factor, Foxo1, fine-tunes sensitivity to homeostatic signals during calorie restriction in CD8+ cytotoxic T cells (P1292)

In addition to longevity enhancement, calorie restriction has been reported to slow the appearance of aging-related T cell abnormalities. However, the molecular mechanism underlying this phenomenon is ill-defined. We report that short-term calorie restriction in mice conferred protection to naïve CD8+ T cells from death-by-neglect, as compared to cells isolated from mice fed ad libitum. An ortholog of the forkhead transcription factor, Foxo1, is required for the longevity benefits of calorie restriction in C. elegans. Therefore, mice with a conditional, T cell-specific deficiency of Foxo1 were also subjected to calorie restriction. Calorie restriction in the absence of Foxo1 did not result in reduced naïve CD8+ T cell death by neglect. Naïve CD8+ T cells isolated from calorie restricted mice express higher levels of the cell surface receptors, CD8 and CD127, both of which are responsible for receiving homeostatic survival signals in vivo. Thus, Foxo1 coordinates an intrinsic transcriptional response to calorie restriction that alters the sensitivity of naïve CD8+ T cells to homeostatic signals. Additional studies revealed that full calorie restriction (as opposed to restricting one component of the diet) is required for this phenomenon. To our knowledge, Foxo1 is the first transcription factor identified to contribute to altered naïve CD8+ T cell homeostasis during calorie restriction in mice.

The forkhead transcription factor, Foxo1, coordinates an adaptive, pro-survival response to calorie restriction in T cells (47.3)

In addition to longevity enhancement, calorie restriction has been reported to slow the appearance of aging-related T cell abnormalities. However, the molecular mechanism underlying this phenomenon in T cells is ill-defined. We report that short-term calorie restriction in wild type mice inhibited the spontaneous apoptosis of naïve CD8+ T cells by approximately three fold, as compared to cells isolated from mice fed ad libitum. An ortholog of the forkhead transcription factor, Foxo1, is required for the longevity benefits of calorie restriction in C. elegans. Therefore, mice with a conditional, T cell-specific deficiency of Foxo1 (Foxo1 cKO) were also subjected to calorie restriction. Indeed, the pathway through which calorie restriction results in reduced naïve CD8+ T cell apoptosis appears to involve Foxo1, as calorie restriction in the absence of Foxo1 did not result in reduced naïve CD8+ T cell apoptosis. Instead, naïve CD8+ T cell apoptosis was similarly high for cells isolated from ad libitum wild type, ad libitum Foxo1 cKO, and calorie restricted Foxo1 cKO mice. Thus, Foxo1 coordinates an adaptive, pro-survival transcriptional response to calorie restriction. To our knowledge, Foxo1 is the first transcription factor identified to contribute to this process in mice.

Successful integration of practical flow cytometric experience into undergraduate education. (51.4)

Flow cytometry is an essential tool in almost every discipline of cell biology, and is increasingly utilized in a variety of other associated yet diverse fields, including molecular biology, bioengineering, microbiology and marine biology. For many years, access to the use of flow cytometers as teaching tools, even in large universities, was limited to graduate programs, due to the cost of instrument purchase and maintenance, and to the complexity of operation. Recently, several affordable, bench-top flow cytometers have appeared on the market. The affordability and user-friendly nature of these instruments have made them attractive to the faculty of various departments at medium- and small-sized universities and colleges for use both as teaching tools and in faculty research projects. We have compiled information here on the funding sources for both purchase and maintenance of these instruments at our various institutions, and share information on applications, protocols and lab exercises that have worked well with our students. Example protocols described include applications such as immunophenotyping, apoptosis (annexin/propidium iodide), monocytic phagocytosis, intracellular and mitochondrial reactive oxygen species detection, and detection of fluorescent protein expression in bacteria.

Investigating the involvement of Foxo1 in T cell repertoire diversity (160.8)

Advanced age is associated with increased susceptibility to and mortality from infectious diseases, especially influenza and pneumonia; and vaccination responses in the elderly are diminished. Declining resistance to infection in aging individuals is correlated with a progressive decline in the size and repertoire of the T cell pool. A better understanding of the mechanisms underlying age-related deterioration of T cell immunity could inform therapies that enhance general immune function and vaccination effectiveness in this vulnerable population. The forkhead transcription factor, Foxo1, has recently been identified as a major regulator of naïve T cell homeostasis. Moreover, a Foxo1 homolog, DAF-16, promotes longevity in C. elegans. Therefore, these studies documented the repertoire diversity of splenic CD4+ and CD8+ T cells in mice selectively deficient for Foxo1 in the T cell compartment (Foxo1 cKO mice). Our studies indicate that T cell-specific Foxo1 deficiency impacts TCR diversity in both the CD4+ and CD8+ splenic T cell populations of young mice. These observations suggest the intriguing possibility that in mice, Foxo1 may participate in aging-related changes in T cell diversity.

Investigating the involvement of Foxo1 in T cell ageing (132.1)

Advanced age is associated with increased susceptibility to and mortality from infectious diseases, especially influenza and pneumonia; and vaccination responses in the elderly are diminished. Declining resistance to infection in aging individuals is correlated with a progressive decline in the size and functionality of the naïve T cell pool. A better understanding of the mechanisms underlying age-related deterioration of T cell immunity could inform therapies that enhance general immune function and vaccination effectiveness in this vulnerable population. The forkhead transcription factor, Foxo1, has recently been identified as a major regulator of naïve T cell homeostasis. Moreover, a Foxo1 homolog, DAF-16, promotes longevity in C. elegans. Therefore, these studies documented the decline of the naïve T cell pool in mice selectively deficient for Foxo1 in the T cell compartment (Foxo1 cKO mice) to determine the involvement of Foxo1 in ageing T cells. Our studies indicate that naïve CD8+ CD122- T cells decline at a more rapid rate in the blood of Foxo1 cKO mice as compared to WT controls. Together, these observations suggest the intriguing possibility that in mice, Foxo1 may be involved in retarding age-related deterioration of T cell immunity.

Female and male sex hormones differentially regulate expression of Ifi202, an interferon-inducible lupus susceptibility gene within the Nba2 interval

Increased expression of IFN-inducible Ifi202 gene in certain strains of female mice is associated with susceptibility to systemic lupus erythematosus (SLE). Although, the development of SLE is known to have a strong sex bias, the molecular mechanisms remain unknown. Here we report that in vivo treatment of orchiectomized (NZB x NZW)F(1) male mice with the female sex hormone 17beta-estradiol significantly increased steady-state levels of Ifi202 mRNA in splenic cells, whereas treatment with the male hormone dihydrotestosterone decreased the levels. Moreover, increased expression of Ifi202 in B6.Nba2 B cells and reduced expression in T cells were associated with increased levels of estrogen receptor-alpha (ERalpha) and androgen receptor, respectively. Furthermore, the steady-state levels of Ifi202 mRNA were higher in splenic cells from C57BL/6, B6.Nba2, NZB, and (NZB x NZW)F(1) female mice as compared with males. 17beta-estradiol treatment of B cells and WT276 cells increased Ifi202 mRNA levels, whereas treatment with dihydrotestosterone decreased the levels. Interestingly, overexpression of ERalpha in WT276 cells increased the expression of Ifi202 and stimulated the activity of the 202-luc-reporter through the c-Jun/AP-1 DNA-binding site. Accordingly, ERalpha preferentially associated with the regulatory region of the Ifi202 gene in female B6.Nba2 B cells than in males. Furthermore, Ifi202 mRNA levels were detectable in splenic cells of wild-type (Esr1(+/+)), but not null (Esr1(-/-)), (NZB x NZW)F(1) female mice. Collectively, our observations demonstrate that the female and male sex hormones differentially regulate the expression of Ifi202, thus providing support for the role of Ifi202 in sex bias in SLE.

Mechanisms of PDL1-mediated regulation of autoimmune diabetes

The PD-1-PDL1 pathway plays a critical role in regulating autoimmune diabetes as blockade or deficiency of PD-1 or PDL1 results in accelerated disease in NOD mice. We explored the cellular mechanisms involved in the regulation of these autoimmune responses by investigations involving various gene-deficient mice on the NOD background. Administration of blocking anti-PDL1 antibody to CD4+ T cell-deficient, CD8+ T cell-deficient and B cell-deficient mice demonstrated that PDL1-mediated regulation of autoreactive CD4+ and CD8+ T cells is critical for diabetes development. This concept was confirmed by adoptive transfer studies utilizing lymphocytes from BDC2.5 and 4.1 (CD4+) TCR transgenic mice and 8.3 (CD8+) TCR transgenic mice; efforts showing increased proliferation of both CD4+ and CD8+ T cells following PDL1 blockade in vivo. Furthermore, we observed that anti-PDL1-mediated acceleration is dependent upon events occurring in the pancreatic lymph nodes during early disease stages, but becomes independent of the pancreatic lymph nodes during later disease stages. These data provide strong evidence that PDL1 regulates autoimmune diabetes by limiting the expansion of CD4+ and CD8+ autoreactive T cells, and define the timing and locale of PDL1-mediated regulation of type 1 diabetes.

Insulin-induced remission in new-onset NOD mice is maintained by the PD-1-PD-L1 pathway

The past decade has seen a significant increase in the number of potentially tolerogenic therapies for treatment of new-onset diabetes. However, most treatments are antigen nonspecific, and the mechanism for the maintenance of long-term tolerance remains unclear. In this study, we developed an antigen-specific therapy, insulin-coupled antigen-presenting cells, to treat diabetes in nonobese diabetic mice after disease onset. Using this approach, we demonstrate disease remission, inhibition of pathogenic T cell proliferation, decreased cytokine production, and induction of anergy. Moreover, we show that robust long-term tolerance depends on the programmed death 1 (PD-1)-programmed death ligand (PD-L)1 pathway, not the distinct cytotoxic T lymphocyte-associated antigen 4 pathway. Anti-PD-1 and anti-PD-L1, but not anti-PD-L2, reversed tolerance weeks after tolerogenic therapy by promoting antigen-specific T cell proliferation and inflammatory cytokine production directly in infiltrated tissues. PD-1-PD-L1 blockade did not limit T regulatory cell activity, suggesting direct effects on pathogenic T cells. Finally, we describe a critical role for PD-1-PD-L1 in another powerful immunotherapy model using anti-CD3, suggesting that PD-1-PD-L1 interactions form part of a common pathway to selectively maintain tolerance within the target tissues.