CD4+ Memory T-Cell Formation during Type 1 Immune Responses

Lack of memory recall in human CD4 T cells elicited by the first encounter with SARS-CoV-2

The studies reported here focus on the impact of pre-existing CD4 T cell immunity on the first encounter with SARS-CoV-2. They leverage PBMC samples from plasma donors collected after a first SARS-CoV-2 infection, prior to vaccine availability and compared to samples collected prior to the emergence of SARS-CoV-2. Analysis of CD4 T cell specificity across the entire SARS-CoV-2 proteome revealed that the recognition of SARS-CoV-2-derived epitopes by CD4 memory cells prior to the pandemic are enriched for reactivity toward non-structural proteins conserved across endemic CoV strains. However, CD4 T cells after primary infection with SARS-CoV-2 focus on epitopes from structural proteins. We observed little evidence for preferential recall to epitopes conserved between SARS-CoV-2 and seasonal CoV, a finding confirmed through use of selectively curated conserved and SARS-unique peptides. Our data suggest that SARS-CoV-2 CD4 T cells elicited by the first infection are primarily established from the naive CD4 T cell pool.

Construction of a prognostic model based on memory CD4+ T cell-associated genes for lung adenocarcinoma and its applications in immunotherapy

The association between memory CD4+ T cells and cancer prognosis is increasingly recognized, but their impact on lung adenocarcinoma (LUAD) prognosis remains unclear. In this study, using the cell-type identification by estimating relative subsets of RNA transcripts algorithm, we analyzed immune cell composition and patient survival in LUAD. Weighted gene coexpression network analysis helped identify memory CD4+ T cell-associated gene modules. Combined with module genes, a five-gene LUAD prognostic risk model (HOXB7, MELTF, ABCC2, GNPNAT1, and LDHA) was constructed by regression analysis. The model was validated using the GSE31210 data set. The validation results demonstrated excellent predictive performance of the risk scoring model. Correlation analysis was conducted between the clinical information and risk scores of LUAD samples, revealing that LUAD patients with disease progression exhibited higher risk scores. Furthermore, univariate and multivariate regression analyses demonstrated the model independent prognostic capability. The constructed nomogram results demonstrated that the predictive performance of the nomogram was superior to the prognostic model and outperformed individual clinical factors. Immune landscape assessment was performed to compare different risk score groups. The results revealed a better prognosis in the low-risk group with higher immune infiltration. The low-risk group also showed potential benefits from immunotherapy. Our study proposes a memory CD4+ T cell-associated gene risk model as a reliable prognostic biomarker for personalized treatment in LUAD patients.

IL-15 Complex-Induced IL-10 Enhances Plasmodium-specific CD4+ T Follicular Helper Differentiation and Antibody Production

Malaria, which results from infection with Plasmodium parasites, remains a major public health problem. Although humans do not develop long-lived, sterilizing immunity, protection against symptomatic disease develops after repeated exposure to Plasmodium parasites and correlates with the acquisition of humoral immunity. Despite the established role Abs play in protection from malaria disease, dysregulated inflammation is thought to contribute to the suboptimal immune response to Plasmodium infection. Plasmodium berghei ANKA (PbA) infection results in a fatal severe malaria disease in mice. We previously demonstrated that treatment of mice with IL-15 complex (IL-15C; IL-15 bound to an IL-15Rα-Fc fusion protein) induces IL-10 expression in NK cells, which protects mice from PbA-induced death. Using a novel MHC class II tetramer to identify PbA-specific CD4+ T cells, in this study we demonstrate that IL-15C treatment enhances T follicular helper (Tfh) differentiation and modulates cytokine production by CD4+ T cells. Moreover, genetic deletion of NK cell-derived IL-10 or IL-10R expression on T cells prevents IL-15C-induced Tfh differentiation. Additionally, IL-15C treatment results in increased anti-PbA IgG Ab levels and improves survival following reinfection. Overall, these data demonstrate that IL-15C treatment, via its induction of IL-10 from NK cells, modulates the dysregulated inflammation during Plasmodium infection to promote Tfh differentiation and Ab generation, correlating with improved survival from reinfection. These findings will facilitate improved control of malaria infection and protection from disease by informing therapeutic strategies and vaccine design.

The Role of Oxidative Stress in Tumorigenesis and Progression

Oxidative stress refers to the imbalance between the production of reactive oxygen species (ROS) and the endogenous antioxidant defense system. Its involvement in cell senescence, apoptosis, and series diseases has been demonstrated. Advances in carcinogenic research have revealed oxidative stress as a pivotal pathophysiological pathway in tumorigenesis and to be involved in lung cancer, glioma, hepatocellular carcinoma, leukemia, and so on. This review combs the effects of oxidative stress on tumorigenesis on each phase and cell fate determination, and three features are discussed. Oxidative stress takes part in the processes ranging from tumorigenesis to tumor death via series pathways and processes like mitochondrial stress, endoplasmic reticulum stress, and ferroptosis. It can affect cell fate by engaging in the complex relationships between senescence, death, and cancer. The influence of oxidative stress on tumorigenesis and progression is a multi-stage interlaced process that includes two aspects of promotion and inhibition, with mitochondria as the core of regulation. A deeper and more comprehensive understanding of the effects of oxidative stress on tumorigenesis is conducive to exploring more tumor therapies.

Elimination of Chlamydia muridarum from the female reproductive tract is IL-12p40 dependent, but independent of Th1 and Th2 cells

Chlamydia vaccine approaches aspire to induce Th1 cells for optimal protection, despite the fact that there is no direct evidence demonstrating Th1-mediated Chlamydia clearance from the female reproductive tract (FRT). We recently reported that T-bet-deficient mice can resolve primary Chlamydia infection normally, undermining the potentially protective role of Th1 cells in Chlamydia immunity. Here, we show that T-bet-deficient mice develop robust Th17 responses and that mice deficient in Th17 cells exhibit delayed bacterial clearance, demonstrating that Chlamydia-specific Th17 cells represent an underappreciated protective population. Additionally, Th2-deficient mice competently clear cervicovaginal infection. Furthermore, we show that sensing of IFN-γ by non-hematopoietic cells is essential for Chlamydia immunity, yet bacterial clearance in the FRT does not require IFN-γ secretion by CD4 T cells. Despite the fact that Th1 cells are not necessary for Chlamydia clearance, protective immunity to Chlamydia is still dependent on MHC class-II-restricted CD4 T cells and IL-12p40. Together, these data point to IL-12p40-dependent CD4 effector maturation as essential for Chlamydia immunity, and Th17 cells to a lesser extent, yet neither Th1 nor Th2 cell development is critical. Future Chlamydia vaccination efforts will be more effective if they focus on induction of this protective CD4 T cell population.

CD4+ T cell memory

Specialized subpopulations of CD4+ T cells survey major histocompatibility complex class II-peptide complexes to control phagosomal infections, help B cells, regulate tissue homeostasis and repair or perform immune regulation. Memory CD4+ T cells are positioned throughout the body and not only protect the tissues from reinfection and cancer, but also participate in allergy, autoimmunity, graft rejection and chronic inflammation. Here we provide updates on our understanding of the longevity, functional heterogeneity, differentiation, plasticity, migration and human immunodeficiency virus reservoirs as well as key technological advances that are facilitating the characterization of memory CD4+ T cell biology.

Contribution of adaptive immunity to human COPD and experimental models of emphysema

The pathophysiology of chronic obstructive pulmonary disease (COPD) and the undisputed role of innate immune cells in this condition have dominated the field in the basic research arena for many years. Recently, however, compelling data suggesting that adaptive immune cells may also contribute to the progressive nature of lung destruction associated with COPD in smokers have gained considerable attention. The histopathological changes in the lungs of smokers can be limited to the large or small airways, but alveolar loss leading to emphysema, which occurs in some individuals, remains its most significant and irreversible outcome. Critically, however, the question of why emphysema progresses in a subset of former smokers remained a mystery for many years. The recognition of activated and organized tertiary T- and B-lymphoid aggregates in emphysematous lungs provided the first clue that adaptive immune cells may play a crucial role in COPD pathophysiology. Based on these findings from human translational studies, experimental animal models of emphysema were used to determine the mechanisms through which smoke exposure initiates and orchestrates adaptive autoreactive inflammation in the lungs. These models have revealed that T helper (Th)1 and Th17 subsets promote a positive feedback loop that activates innate immune cells, confirming their role in emphysema pathogenesis. Results from genetic studies and immune-based discoveries have further provided strong evidence for autoimmunity induction in smokers with emphysema. These new findings offer a novel opportunity to explore the mechanisms underlying the inflammatory landscape in the COPD lung and offer insights for development of precision-based treatment to halt lung destruction.

Subset-specific and temporal control of effector and memory CD4+ T cell survival

Following their proliferative expansion and differentiation into effector cells like Th1, Tfh, and T central memory precursors (Tcmp), most effector CD4+ T cells die, while some survive and become memory cells. Here, we explored how Bcl-2 family members controlled the survival of CD4+ T cells during distinct phases of mouse acute LCMV infection. During expansion, we found that Th1 cells dominated the response, downregulated expression of Bcl-2, and did not require Bcl-2 for survival. Instead, they relied on the anti-apoptotic protein, A1 for survival. Similarly, Th17 cells in an EAE model also depended on A1 for survival. However, after the peak of the response, CD4+ effector T cells required Bcl-2 to counteract Bim to aid their transition into memory. This Bcl-2 dependence persisted in established memory CD4+ T cells. Combined, these data show a temporal switch in Bcl-2 family-mediated survival of CD4+ T cells over the course of an immune response. This knowledge can help improve T cell survival to boost immunity and conversely, target pathogenic T cells.

Role of Th17 cells, Treg cells, and Th17/Treg imbalance in immune homeostasis disorders in patients with chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death worldwide, following strokes and cardiovascular diseases. Chronic lung inflammation is believed to play a role in the development of COPD. In addition, accumulating evidence shows that the immune system plays a crucial role in the pathogenesis of COPD. Significant advancements have been made in research on the pathogenesis of immune diseases and chronic inflammation in recent years, and T helper 17 (Th17) cells and regulatory T (Treg) cells have been found to play a crucial role in the autoimmune response. Th17 cells are a proinflammatory subpopulation that causes autoimmune disease and tissue damage. Treg cells, on the other hand, have a negative effect but can contribute to the occurrence of the same disease when their antagonism fails. This review mainly summarizes the biological characteristics of Th17 cells and Treg cells, their roles in chronic inflammatory diseases of COPD, and the role of the Th17/Treg ratio in the onset, development, and outcome of inflammatory disorders, as well as recent advancements in immunomodulatory treatment targeting Th17/Treg cells in COPD.

Control of Memory Phenotype T Lymphocyte Homeostasis: Role of Costimulation

Foxp3⁺ T regulatory cells (Tregs), CD4⁺Foxp3^- T cells, and CD8⁺ T cells are composed of naive phenotype (NP) and memory phenotype (MP) subsets. Ten to 20% of each MP T cell population are cycling (Ki-67⁺) in vivo. We investigated the contribution of costimulatory (CD28) and coinhibitory (CTLA-4, PD-1) receptors on MP T cell homeostatic proliferation in vivo in the mouse. Blockade of CD28-CD80/CD86 signaling completely abolished MP Tregs and profoundly inhibited MP CD4⁺Foxp3^- T cell proliferation, but it did not affect MP CD8⁺ T cell proliferation. Marked enhancement of homeostatic proliferation of MP Tregs and MP CD4⁺Foxp3^- T cells was seen after blocking CTLA4-CD80/CD86 interactions and PD-1-PD-L1/2 interactions, and greater enhancement was seen with blockade of both pathways. The CD28 pathway also played an important role in the expansion of Tregs and MP T cells after treatment of mice with agonistic Abs to members of the TNF receptor superfamily, which can act directly (anti-GITR, anti-OX40, anti-4-1BB) or indirectly (anti-CD40) on T cells. Induction of a cytokine storm by blocking the interaction of NK inhibitory receptors with MHC class I had no effect on Treg homeostasis, enhanced MP CD4⁺ proliferation, and expansion in a CD28-dependent manner, but it enhanced MP CD8⁺ T cell proliferation in a CD28-independent manner. Because MP T cells exert potent biologic effects primarily before the induction of adaptive immune responses, these findings have important implications for the use of biologic agents designed to suppress autoimmune disease or enhance T effector function in cancer that may have negative effects on MP T cells.

Making memories with Bcl-6

For over a decade, mutual antagonism between the transcriptional repressors Bcl-6 and Blimp-1 has been appreciated as a key mechanistic determinant of lymphoid differentiation programs. Now, in this issue of JEM, Ciucci et al. (2021. J. Exp. Med.https://doi.org/10.1084/jem.20202343) demonstrate that this relationship is "central" to the generation of T cell memory.

Identification and Validation of a Tumor Microenvironment-Related Gene Signature in Hepatocellular Carcinoma Prognosis

Background: Hepatocellular carcinoma (HCC) is a typical inflammatory-related malignant tumor with complex immune tolerance microenvironment and poor prognosis. In this study, we aimed to construct a novel immune-related gene signature for the prognosis of HCC patients, exploring tumor microenvironment (TME) cell infiltration characterization and potential mechanisms. Methods: A total of 364 HCC samples with follow-up information in the TCGA-LIHC dataset were analyzed for the training of the prognostic signature. The Least Absolute Shrinkage and Selector Operation (LASSO) regression based on the IRGs was conducted to identify the prognostic genes and establish an immune risk signature. The immune cell infiltration in TME was estimated via the CIBERSORT method. Gene Set Variation Analysis (GSVA) was conducted to compare the biological pathways involved in the low-risk and high-risk groups. Furthermore, paraffin sections of HCC tissue microarrays containing 77 patients from Fudan University Shanghai Cancer Center were used for IHC staining. The clinical characteristics of the 77 HCC patients were collected and summarized for survival analysis validation via the Kaplan-Meier (KM) method. Results: Three-gene signature with close immune correlation (Risk score = EPO * 0.02838 + BIRC5 * 0.02477 + SPP1 * 0.0002044) was constructed eventually and proven to be an effective prognostic factor for HCC patients. The patients were divided into a high-risk and a low-risk group according to the optimal cutoff, and the survival analysis revealed that HCC samples with high-risk immuno-score had significantly poorer outcomes than the low-risk group (p < 0.0001). The results of CIBERSORT suggested that the immune cell activation was relatively higher in the low-risk group with better prognosis. Besides, GSVA analysis showed multiple signaling differences between the high- and low-risk group, indicating that the three-gene prognostic model can affect the prognosis of patients by affecting immune-related mechanisms. Tissue microarray (TMA) results further confirmed that the expression of three genes in HCC tissues was closely related to the prognosis of patients, respectively. Conclusion: In this study, we constructed and validated a robust three-gene signature with close immune correlation in HCC, which presented a reliable performance in the prediction of HCC patients' survival.