CXCR5+ CD8 T Cells: Protective or Pathogenic?

Follicular CD8+ T cells promote immunoglobulin production and demyelination in multiple sclerosis and a murine model

Emerging evidence underscores the importance of CD8+ T cells in the pathogenesis of multiple sclerosis (MS), but the precise mechanisms remain ambiguous. This study intends to elucidate the involvement of a novel subset of follicular CD8+ T cells (CD8+CXCR5+ T) in MS and an experimental autoimmune encephalomyelitis (EAE) murine model. The expansion of CD8+CXCR5+ T cells was observed in both MS patients and EAE mice during the acute phase. In relapsing MS patients, higher frequencies of circulating CD8+CXCR5+ T cells were positively correlated with new gadolinium-enhancement lesions in the central nervous system (CNS). In EAE mice, frequencies of CD8+CXCR5+ T cells were also positively correlated with clinical scores. These cells were found to infiltrate into ectopic lymphoid-like structures in the spinal cords during the peak of the disease. Furthermore, CD8+CXCR5+ T cells, exhibiting high expression levels of ICOS, CD40L, IL-21, and IL-6, were shown to facilitate B cell activation and differentiation through a synergistic interaction between CD40L and IL-21. Transferring CD8+CXCR5+ T cells into naïve mice confirmed their ability to enhance the production of anti-MOG35-55 antibodies and contribute to the disease progression. Consequently, CD8+CXCR5+ T cells may play a role in CNS demyelination through heightening humoral immune responses.

Lombana C, Beiting D, Novais F, P. Carvalho L, M. Carvalho E, Scott P. CCR5 promotes the migration of pathological CD8+ T cells to the leishmanial lesions

Cytolytic CD8+ T cells mediate immunopathology in cutaneous leishmaniasis without controlling parasites. Here, we identify factors involved in CD8+ T cell migration to the lesion that could be targeted to ameliorate disease severity. CCR5 was the most highly expressed chemokine receptor in patient lesions, and the high expression of CCL3 and CCL4, CCR5 ligands, was associated with delayed healing of lesions. To test the requirement for CCR5, Leishmania-infected Rag1-/- mice were reconstituted with CCR5-/- CD8+ T cells. We found that these mice developed smaller lesions accompanied by a reduction in CD8+ T cell numbers compared to controls. We confirmed these findings by showing that the inhibition of CCR5 with maraviroc, a selective inhibitor of CCR5, reduced lesion development without affecting the parasite burden. Together, these results reveal that CD8+ T cells migrate to leishmanial lesions in a CCR5-dependent manner and that blocking CCR5 prevents CD8+ T cell-mediated pathology.

Bridging the gender gap in autoimmunity with T-cell-targeted biomaterials

Autoimmune diseases are caused by malfunctions of the immune system and generally impact women at twice the frequency of men. Many of the most serious autoimmune diseases are accompanied by a dysregulation of T-cell phenotype, both regarding the ratio of CD4+ to CD8+ T-cells and proinflammatory versus regulatory phenotypes. Biomaterials, in the form of particles and hydrogels, have shown promise in ameliorating this dysregulation both in vivo and ex vivo. In this review, we explore the role of T-cells in autoimmune diseases, particularly those with high incidence rates in women, and evaluate the promise and efficacy of innovative biomaterial-based approaches for targeting T-cells.

An angel or a devil? Current view on the role of CD8+ T cells in the pathogenesis of myasthenia gravis

BACKGROUND

Myasthenia gravis (MG) and the experimental autoimmune MG (EAMG) animal model are characterized by T-cell-induced and B-cell-dominated autoimmune diseases that affect the neuromuscular junction. Several subtypes of CD4+ T cells, including T helper (Th) 17 cells, follicular Th cells, and regulatory T cells (Tregs), contribute to the pathogenesis of MG. However, increasing evidence suggests that CD8+ T cells also play a critical role in the pathogenesis and treatment of MG.

MAIN BODY

Herein, we review the literature on CD8+ T cells in MG, focusing on their potential effector and regulatory roles, as well as on relevant evidence (peripheral, in situ, cerebrospinal fluid, and under different treatments), T-cell receptor usage, cytokine and chemokine expression, cell marker expression, and Treg, Tc17, CD3+CD8+CD20+ T, and CXCR5+ CD8+ T cells.

CONCLUSIONS

Further studies on CD8+ T cells in MG are necessary to determine, among others, the real pattern of the Vβ gene usage of autoantigen-specific CD8+ cells in patients with MG, real images of the physiology and function of autoantigen-specific CD8+ cells from MG/EAMG, and the subset of autoantigen-specific CD8+ cells (Tc1, Tc17, and IL-17+IFN-γ+CD8+ T cells). There are many reports of CD20-expressing T (or CD20 + T) and CXCR5+ CD8 T cells on autoimmune diseases, especially on multiple sclerosis and rheumatoid arthritis. Unfortunately, up to now, there has been no report on these T cells on MG, which might be a good direction for future studies.

T-cell subset changes during the first year of pre-seasonal allergoid allergen-specific immunotherapy

Allergen-specific immunotherapy (AIT) is the only treatment for type I allergy, which achieves long-lasting effects. Repeated subcutaneous applications of allergen extracts cause a protective antibody response and an immune deviation of T cells. In AIT with allergoids, chemically modified allergen extracts are injected. During a so-called special pre-seasonal application scheme, after the initial phase of applying increased doses of allergoids is followed by natural allergen exposure as a maintenance phase. The effectiveness of allergoid vaccines has been described regarding the improvement of clinical symptoms and the development of protective humoral responses. In this longitudinal observational study, we sought to investigate changes at the T cell level in pre-seasonal AIT with allergoid. Different subsets within CD4+ and CD8+ T cells were monitored by flow cytometry in PBMC of patients known to possess protective antibody responses. Compared to before treatment, a small early boost among allergenic Th cells was observed after 4 months of AIT. In line, a slight Th2 bias was observed after 4 months within circulating T follicular T cells, Tfh and Tfc, representing pre-existing memory Th2 cells. Furthermore, it was demonstrated that responsiveness of CD8+ T cells to allergen stimulation decreased during the course of treatment. Apart from that, we found an influence of the meteorological season on the activation profile of Tfh and Tfc over the course of the treatment. Together, this is the first study investigating changes of different T cell subsets over the course of an allergoid AIT against airborne allergens. Our findings match previous reports on conventional AIT, especially the initial increase of Th2 responses. However, the observed changes were less pronounced which may be either due to the modification of allergens or to the reduced maintenance dose provided by natural allergen exposure compared to a perennial protocol.

CCR5 promotes the migration of CD8+ T cells to the leishmanial lesions

Cytolytic CD8+ T cells mediate immunopathology in cutaneous leishmaniasis without controlling parasites. Here, we identify factors involved in CD8+ T cell migration to the lesion that could be targeted to ameliorate disease severity. CCR5 was the most highly expressed chemokine receptor in patient lesions, and the high expression of CCL3 and CCL4, CCR5 ligands, was associated with delayed healing of lesions. To test the requirement for CCR5, Leishmania-infected Rag1-/- mice were reconstituted with CCR5-/- CD8+ T cells. We found that these mice developed smaller lesions accompanied by a reduction in CD8+ T cell numbers compared to controls. We confirmed these findings by showing that the inhibition of CCR5 with maraviroc, a selective inhibitor of CCR5, reduced lesion development without affecting the parasite burden. Together, these results reveal that CD8+ T cells migrate to leishmanial lesions in a CCR5-dependent manner and that blocking CCR5 prevents CD8+ T cell-mediated pathology.

Dissecting the Protective Effect of CD8+ T Cells in Response to SARS-CoV-2 mRNA Vaccination and the Potential Link with Lymph Node CD8+ T Cells

SARS-CoV-2 vaccines have played a crucial role in effectively reducing COVID-19 disease severity, with a new generation of vaccines that use messenger RNA (mRNA) technology being administered globally. Neutralizing antibodies have featured as the heroes of vaccine-induced immunity. However, vaccine-elicited CD8⁺ T cells may have a significant impact on the early protective effects of the mRNA vaccine, which are evident 12 days after initial vaccination. Vaccine-induced CD8⁺ T cells have been shown to respond to multiple epitopes of SARS-CoV-2 and exhibit polyfunctionality in the periphery at the early stage, even when neutralizing antibodies are scarce. Furthermore, SARS-CoV-2 mRNA vaccines induce diverse subsets of memory CD8⁺ T cells that persist for more than six months following vaccination. However, the protective role of CD8⁺ T cells in response to the SARS-CoV-2 mRNA vaccines remains a topic of debate. In addition, our understanding of CD8⁺ T cells in response to vaccination in the lymph nodes, where they first encounter antigen, is still limited. This review delves into the current knowledge regarding the protective role of polyfunctional CD8⁺ T cells in controlling the virus, the response to SARS-CoV-2 mRNA vaccines, and the contribution to supporting B cell activity and promoting immune protection in the lymph nodes.

IL-21, Inflammatory Cytokines and Hyperpolarized CD8+ T Cells Are Central Players in Lupus Immune Pathology

Systemic lupus erythematous (SLE) is a chronic autoimmune disorder, broadly characterized by systemic inflammation along with heterogeneous clinical manifestations, severe morbidity, moribund organ failure and eventual mortality. In our study, SLE patients displayed a higher percentage of activated, inflamed and hyper-polarized CD8⁺ T cells, dysregulated CD8⁺ T cell differentiation, significantly elevated serum inflammatory cytokines and higher accumulation of cellular ROS when compared to healthy controls. Importantly, these hyper-inflammatory/hyper-polarized CD8⁺ T cells responded better to an antioxidant than to an oxidant. Terminally differentiated Tc1 cells also showed plasticity upon oxidant/antioxidant treatment, but that was in contrast to the SLE CD8⁺ T cell response. Our studies suggest that the differential phenotype and redox response of SLE CD8⁺ T cells and Tc1 cells could be attributed to their cytokine environs during their respective differentiation and eventual activation environs. The polarization of Tc1 cells with IL-21 drove hyper-cytotoxicity without hyper-polarisation suggesting that the SLE inflammatory cytokine environment could drive the extreme aberrancy in SLE CD8⁺ T cells.

Follicular CD8+ T Cells Are Elevated in HIV Infection and Induce PD-L1 on B Cells

Follicular CD8+CXCR5+ T cells are a specialized CD8+ T cell subset with unique follicular-homing capabilities that have been reported to display effector functions in viral immunity, tumor immunity, and autoimmunity. CD8+CXCR5+ T cells exhibit B cell helper functions and express CD40L, ICOS, programmed cell death protein 1 (PD-1), and BCL-6, the transcriptional regulator of CD4+CXCR5+ T follicular helper cells and of germinal center B cells. HIV is known to be sequestered in lymphoid follicles, and CD8+CXCR5+ T cell frequency is a marker for disease severity, given that HIV-infected patients with lower numbers of circulating CD8+CXCR5+ T cells display lower CD4+ T cell counts. Likewise, several groups have reported a direct correlation between the quantity of CD8+CXCR5+ T cells and suppression of HIV viral load. In this study, we observed elevated absolute numbers of CD8+CXCR5+ and CD8+CXCR5+BCL-6+PD-1+ T cells in the blood of HIV-infected participants of the Multicenter AIDS Cohort Study. We further demonstrated in vitro that activated human CD8+CXCR5+ T cells isolated from peripheral blood and tonsil from healthy donors show increased CD40L expression and induce the production of PD ligand 1 (PD-L1)+IgG+ B cells. Moreover, absolute numbers of CD8+CXCR5+ T cells significantly and positively correlated with numbers of PD-L1+ B cells found in blood of HIV-infected individuals. Altogether, these results show that activated CD8+CXCR5+ T cells have the ability to activate B cells and increase the percentage of PD-L1+ and PD-L1+IgG+ B cells, which provides insights into the early events of B cell activation and differentiation and may play a role in disease progression and lymphomagenesis in HIV-infected individuals.

Characterization of C-X-C chemokine receptor type 5 in the cornea and role in the inflammatory response after corneal injury

C-X-C chemokine receptor type 5 (CXCR5) regulates inflammatory responses in ocular and non-ocular tissues. However, its expression and role in the cornea are still unknown. Here, we report the expression of CXCR5 in human cornea in vitro and mouse corneas in vivo, and its functional role in corneal inflammation using C57BL/6J wild-type (CXCR5^+/+) and CXCR5-deficient (CXCR5^-/-) mice, topical alkali injury, clinical eye imaging, histology, immunofluorescence, PCR, qRT-PCR, and western blotting. Human corneal epithelial cells, stromal fibroblasts, and endothelial cells demonstrated CXCR5 mRNA and protein expression in PCR, and Western blot analyses, respectively. To study the functional role of CXCR5 in vivo, mice were divided into four groups: Group-1 (CXCR5^+/+ alkali injured cornea; n = 30), Group-2 (CXCR5^-/- alkali injured cornea; n = 30), Group-3 (CXCR5^+/+ naïve cornea; n = 30), and Group-4 (CXCR5^-/- naïve cornea; n = 30). Only one eye was wounded with alkali. Clinical corneal evaluation and imaging were performed before and after injury. Mice were euthanized 4 h, 3 days, or 7 days after injury, eyes were excised and used for histology, immunofluorescence, and qRT-PCR. In clinical eye examinations, CXCR5^-/- mouse corneas showed ocular health akin to the naïve corneas. Alkali injured CXCR5^+/+ mouse corneas showed significantly increased mRNA (p < 0.001) and protein (p < 0.01 or p < 0.0001) levels of the CXCR5 compared to the naïve corneas. Likewise, alkali injured CXCR5^-/- mouse corneas showed remarkably amplified inflammation in clinical eye exams in live animals. The histological and molecular analyses of these corneas post euthanasia exhibited markedly augmented inflammatory cells in H&E staining and significant CD11b + cells in immunofluorescence (p < 0.01 or < 0.05); and tumor necrosis factor-alpha (TNFα; p < 0.05), cyclooxygenase 2 (COX-2; p < 0.0001), interleukin (IL)-1β (p < 0.0001), and IL-6 (p < 0.0001 or < 0.01) mRNA expression compared to the CXCR5^+/+ mouse corneas. Interestingly, CXCR5^-/- alkali injured corneas also showed altered mRNA expression of fibrotic alpha smooth muscle actin (α-SMA; p > 0.05) and angiogenic vascular endothelial growth factor (VEGF; p < 0.01) compared to the CXCR5^+/+ alkali injured corneas. In summary, the CXCR5 gene is expressed in all three major layers of the cornea and appears to influence corneal inflammatory and repair events post-injury in vivo. More studies are warranted to tease the mechanistic role of CXCR5 in corneal inflammation and wound healing.

Extensive Phenotypic Characterization of T Cells Infiltrating Liver Metastasis from Colorectal Cancer: A Potential Role in Precision Medicine

Colorectal cancer (CRC) is one of the most common cancers worldwide, with liver metastasis being its main cause of death. This study harvested fresh biological material from non-tumor and tumor tissue from 47 patients with CRC liver metastasis after surgery, followed by mechanical cellular extraction and stain-lyse-wash direct immunofluorescence technique. Here, 60 different T-cell populations were characterized by flow cytometry. Tumor samples were also subdivided according to their growth pattern into desmoplastic and non-desmoplastic. When we compared tumor versus non-tumor samples, we observed a significantly lower percentage of T-lymphocyte infiltration in the tumor in which the CD4⁺ T-cell density increased compared to the CD8⁺ T cells. T regulatory cells also increased within the tumor, even with an activated phenotype (HLA-DR⁺). A higher percentage of IL-17-producing cells was present in tumor samples and correlated with the metastasis size. In contrast, we also observed a significant increase in CD8⁺ follicular-like T cells (CD185⁺), suggesting a cytotoxic response to cancer cells. Additionally, most infiltrated T cells exhibit an intermediate activation phenotype (CD25⁺). In conclusion, our results revealed potential new targets and prognostic biomarkers that could take part in an algorithm for personalized medicine approaches improving CRC patients' outcomes.

CXCR5+CD8 T cells: Potential immunotherapy targets or drivers of immune-mediated adverse events?

CXCR5⁺CD8 T cells have attracted significant interest within multiple areas of immunology, cancer, and infection. This is in part due to their apparent dual functionality. These cells perform as cytotoxic cells in a variety of infection states including LCMV, HBV, HIV and SIV. However, CXCR5⁺CD8 T cells also associate with B cells in peripheral organs and function to stimulate B cell proliferation, antibody/B cell receptor class-switch, and antibody production. CXCR5⁺CD8 T cells are similar to CXCR5⁺CD4 T follicular helpers in their genetic make-up, B cell interactions, and functionality despite possessing elevated programmed cell death 1 and cytotoxic proteins. Within cancer CXCR5⁺CD8 T cells have risen as potential prognostic markers for overall survival and are functionally cytotoxic within tumor microenvironments. In inflammatory disease and autoimmunity, CXCR5⁺CD8 T cells are implicated in disease progression. During viral infection and cancer, CXCR5 expression on CD8 T cells generally is indicative of progenitor memory stem-like exhausted cells, which are more responsive to immune checkpoint blockade therapy. The use of immune checkpoint inhibitors to overcome immune exhaustion in cancer, and subsequent consequence of immune adverse events, highlights the dual nature of the cellular immune response. This review will detail the functionality of CXCR5⁺CD8 T cells in cancer and autoimmunity with potential repercussions during immune checkpoint blockade therapy discussed.

Heterogenous CD8+ T Cell Maturation and 'Polarization' in Acute and Convalescent COVID-19 Patients

BACKGROUND

The adaptive antiviral immune response requires interaction between CD8+ T cells, dendritic cells, and Th1 cells for controlling SARS-CoV-2 infection, but the data regarding the role of CD8+ T cells in the acute phase of COVID-19 and post-COVID-19 syndrome are still limited.

METHODS

. Peripheral blood samples collected from patients with acute COVID-19 (n = 71), convalescent subjects bearing serum SARS-CoV-2 N-protein-specific IgG antibodies (n = 51), and healthy volunteers with no detectable antibodies to any SARS-CoV-2 proteins (HC, n = 46) were analyzed using 10-color flow cytometry.

RESULTS

Patients with acute COVID-19 vs. HC and COVID-19 convalescents showed decreased absolute numbers of CD8+ T cells, whereas the frequency of CM and TEMRA CD8+ T cells in acute COVID-19 vs. HC was elevated. COVID-19 convalescents vs. HC had increased naïve and CM cells, whereas TEMRA cells were decreased compared to HC. Cell-surface CD57 was highly expressed by the majority of CD8+ T cells subsets during acute COVID-19, but convalescents had increased CD57 on 'naïve', CM, EM4, and pE1 2-3 months post-symptom onset. CXCR5 expression was altered in acute and convalescent COVID-19 subjects, whereas the frequencies of CXCR3+ and CCR4+ cells were decreased in both patient groups vs. HC. COVID-19 convalescents had increased CCR6-expressing CD8+ T cells. Moreover, CXCR3+CCR6- Tc1 cells were decreased in patients with acute COVID-19 and COVID-19 convalescents, whereas Tc2 and Tc17 levels were increased compared to HC. Finally, IL-27 negatively correlated with the CCR6+ cells in acute COVID-19 patients.

CONCLUSIONS

We described an abnormal CD8+ T cell profile in COVID-19 convalescents, which resulted in lower frequencies of effector subsets (TEMRA and Tc1), higher senescent state (upregulated CD57 on 'naïve' and memory cells), and higher frequencies of CD8+ T cell subsets expressing lung tissue and mucosal tissue homing molecules (Tc2, Tc17, and Tc17.1). Thus, our data indicate that COVID-19 can impact the long-term CD8+ T cell immune response.

Development of an Effective Immune Response in Adults With Down Syndrome After Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Vaccination

BACKGROUND

Immune dysregulation in individuals with Down syndrome (DS) leads to an increased risk for hospitalization and death due to coronavirus disease 2019 (COVID-19) and may impair the generation of protective immunity after vaccine administration.

METHODS

The cellular and humoral responses of 55 individuals with DS who received a complete SARS-CoV-2 vaccination regime at 1 to 3 (visit [V 1]) and 6 (V2) months were characterized.

RESULTS

SARS-CoV-2-reactive CD4+ and CD8+ T lymphocytes with a predominant Th1 phenotype were observed at V1 and increased at V2. Likewise, an increase in SARS-CoV-2-specific circulating Tfh (cTfh) cells and CD8+ CXCR5+ PD-1hi lymphocytes was already observed at V1 after vaccine administration. Specific immunoglobulin G (IgG) antibodies against SARS-CoV-2 S protein were detected in 96% and 98% of subjects at V1 and V2, respectively, although IgG titers decreased significantly between both time points.

CONCLUSIONS

Our findings show that DS individuals develop an effective immune response to usual regimes of SARS-CoV-2 vaccination.

T-Follicular-Like CD8+ T Cell Responses in Chronic HIV Infection Are Associated With Virus Control and Antibody Isotype Switching to IgG

T cell responses are considered critical for the in vivo control of HIV, but the contribution of different T cell subsets to this control remains unclear. Using a boosted flow cytometric approach that is able to differentiate CD4+ and CD8+ T cell Th1/Tc1, Th2/Tc2, Th17/Tc17, Treg and Tfh/Tfc-like HIV-specific T cell populations, we identified CD8+ Tfc responses that were related to HIV plasma viral loads and associated with rate of antibody isotype class switching to IgG. This favorable balance towards IgG responses positively correlated with increased virus neutralization, higher avidity of neutralizing antibodies and more potent antibody-dependent cell cytotoxicity (ADCC) in PBMCs from HIV controllers compared to non-controllers. Our results identified the CD8+ Tfc-like T-cell response as a component of effective virus control which could possibly be exploited therapeutically.

Antibody-suppressor CXCR5+ CD8+ T cellular therapy ameliorates antibody-mediated rejection following kidney transplant in CCR5 KO mice

CCR5 KO kidney transplant (KTx) recipients are extraordinarily high alloantibody producers and develop pathology that mimics human antibody-mediated rejection (AMR). C57BL/6 and CCR5 KO mice (H-2^b ) were transplanted with A/J kidneys (H-2^a ); select cohorts received adoptive cell therapy (ACT) with alloprimed CXCR5⁺ CD8⁺ T cells (or control cells) on day 5 after KTx. ACT efficacy was evaluated by measuring posttransplant alloantibody, pathology, and allograft survival. Recipients were assessed for the quantity of CXCR5⁺ CD8⁺ T cells and CD8-mediated cytotoxicity to alloprimed IgG⁺ B cells. Alloantibody titer in CCR5 KO recipients was four-fold higher than in C57BL/6 recipients. The proportion of alloprimed CXCR5⁺ CD8⁺ T cells 7 days after KTx in peripheral blood, lymph node, and spleen was substantially lower in CCR5 KO compared to C57BL/6 recipients. In vivo cytotoxicity towards alloprimed IgG⁺ B cells was also reduced six-fold in CCR5 KO recipients. ACT with alloprimed CXCR5⁺ CD8⁺ T cells (but not alloprimed CXCR5^- CD8⁺ or third-party primed CXCR5⁺ CD8⁺ T cells) substantially reduced alloantibody titer, ameliorated AMR pathology, and prolonged allograft survival. These results indicate that a deficiency in quantity and function of alloprimed CXCR5⁺ CD8⁺ T cells contributes to high alloantibody and AMR in CCR5 KO recipient mice, which can be rescued with ACT.

Exhausted phenotype of circulating CD8+ T cell subsets in hepatitis B virus carriers

Background

Chronic hepatitis B virus (HBV) infection is characterized by the presence of dysfunctional exhausted CD8⁺ T cells that hamper viral control. We investigated the phenotypic heterogeneity of exhausted CD8⁺ T cells in HBV carriers.

Methods

We enrolled 31 HBV carriers and 23 healthy controls (HCs) in our study. Peripheral blood mononuclear cells (PBMCs) were isolated, and flow cytometry was used to determine the phenotypic distribution of CD8⁺ T cell subsets. Expression of cytokines such as TNF-α and IFN-γ was detected by quantitative reverse transcription–PCR, a fluorescence flow cytometry-based immunomicrobead assay and flow cytometry.

Results

There were no significant differences in the baseline characteristics between the 31 HBV carriers and the 23 sex- and age-matched HCs. CD8⁺ T cells exhibited higher levels of inhibitory receptors (TIM3 and PD1) in the HBV carriers than in the HCs (P < 0.05); in particular, Tfc cells (CXCR5⁺CD25⁻) expressed higher levels of TIM3 and PD1 than non-Tfc cells in the HBV carriers. In addition, among the subsets of Tc cells, the Tc17 (CXCR5⁻CD25⁻CCR6⁺) subset displayed increased expression of TIM3 and LAG3 in the HBV carriers. Our findings further showed that CD8⁺ T cells produced lower levels of IFN-γ, TNF-α, and Granzyme B. Paired analysis of the Tfc subset and the Tc subset indicated that higher levels of cytokines (IFN-γ and TNF-α) were produced by the Tfc subset in the HBV carriers. Among the Tc subsets, the Tc17 subset produced lower levels of cytokines.

Conclusion

The Tfc subset exhibited an enhanced exhausted phenotype but possessed some functional properties during chronic HBV infection, while the Tc subset showed a lower functional level. The identification of these unique subsets may provide a potential immunotherapeutic target in chronic HBV infection.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12865-022-00488-2.

The diagnostic role of PD-1+ CXCR5+ follicular helper CD8+ T cell in renal allograft dysfunction

BACKGROUND

The roles of PD-1⁺ CXCR5⁺ follicular helper CD8⁺ T cell were reported in different disease conditions, but their roles in transplantation are unclear. In this study, the association between PD-1⁺ CXCR5⁺ follicular helper CD8⁺ T cell and renal allograft dysfunction in kidney transplant recipients (KTRs) was investigated.

METHODS

82 KTRs were enrolled in this study. 45 KTRs were included in the chronic allograft dysfunction (CAD) group, and 37 KTRs were included in the stable recipients group. Among the CAD group, 12 cases of antibody-mediated rejection (ABMR) and 4 cases of T cell-mediated rejection (TCMR) were diagnosed by biopsy. The percentage of CXCR5⁺ CD8⁺ T cells and the co-expression of signal transducers and activators of transcription 4 (STAT4), STAT5, and PD-1 in peripheral blood were determined by flow cytometry.

RESULTS

The expression of CXCR5 on CD3⁺ CD8⁺ T cells and the percentage of STAT5⁺ CXCR5⁺ cells in the CD3⁺ CD8⁺ T-cell population were significantly lower in the CAD group (p < 0.05), while the expression of PD-1⁺ CXCR5⁺ CD8⁺ T cells was significantly higher (p < 0.05). Through logistic regression analysis, we concluded that the percentage of PD-1⁺ CXCR5⁺ CD8⁺ T cells was an independent risk factor for renal dysfunction. Grouping by pathological type, PD-1⁺ CXCR5⁺ CD8⁺ T cells showed relatively good diagnostic efficacy for ABMR by ROC analysis.

CONCLUSIONS

Our results suggested that PD-1⁺ CXCR5⁺ CD8⁺ T cells were a promising biomarker for distinguishing renal allograft dysfunction and different allograft pathological types. Also, our findings may provide new ways of identifying and treating allograft rejection.

Intrapleural Injection of Anti-PD1 Antibody: A Novel Management of Malignant Pleural Effusion

Background

Malignant tumors accompanied with malignant pleural effusion (MPE) often indicate poor prognosis. The therapeutic effect and mechanism of intrapleural injection of anti-programmed cell death protein 1 (PD1) on MPE need to be explored.

Methods

A preclinical MPE mouse model and a small clinical study were used to evaluate the effect of intrapleural injection of anti-PD1 antibody. The role of immune cells was observed via flow cytometry, RNA-sequencing, quantitative PCR, western blot, immunohistochemistry, and other experimental methods.

Results

Intrathoracic injection of anti-PD1 monoclonal antibody (mAb) has significantly prolonged the survival time of mice (P = 0.0098) and reduced the amount of effusion (P = 0.003) and the number of cancer nodules (P = 0.0043). Local CD8+ T cells participated in intrapleural administration of anti-PD1 mAb. The proportion of CD69+, IFN-γ+, and granzyme B+ CD8+ T cells in the pleural cavity was increased, and the expression of TNF-α and IL-1β in MPE also developed significantly after injection. Local injection promoted activation of the CCL20/CCR6 pathway in the tumor microenvironment and further elevated the expression of several molecules related to lymphocyte activation. Clinically, the control rate of intrathoracic injection of sintilimab (a human anti-PD1 mAb) for 10 weeks in NSCLC patients with MPE was 66.7%. Local injection improved the activity and function of patients' local cytotoxic T cells (CTLs).

Conclusions

Intrapleural injection of anti-PD1 mAb could control malignant pleural effusion and the growth of cancer, which may be achieved by enhancing local CTL activity and cytotoxicity.

RvD1 treatment during primary infection modulates memory response increasing viral load during respiratory viral reinfection

Resolvin D1 (RvD1), which is biosynthesized from essential long-chain fatty acids, is involved in anti-inflammatory activity and modulation of T cell response. Memory CD8+ T cells are important for controlling tumor growth and viral infections. Exacerbated inflammation has been described as impairing memory CD8+ T cell differentiation. This study aimed to verify the effects of RvD1 on memory CD8+ T cells in vitro and in vivo in a respiratory virus infection model. Peripheral blood mononuclear cells were treated at different time points with RvD1 and stimulated with anti-CD3/anti-CD28 antibodies. Pre-treatment with RvD1 increases the expansion of memory CD8+ T cells. The IL-12 level, a cytokine described to control memory CD8+ T cells, was reduced with RvD1 pre-treatment. When the mTOR axis was inhibited, the IL-12 levels were restored. In a respiratory virus infection model, Balb/c mice were treated with RvD1 before infection or after 7 days after infection. RvD1 treatment after infection increased the frequency of memory CD8+ T cells in the lung expressing II4, II10, and Ifng. During reinfection, RvD1-treated and RSV-infected mice present a high viral load in the lung and lower antibody response in the serum. Our results show that RvD1 modulates the expansion and phenotype of memory CD8+ T cells but contributed to a non-protective response after RSV reinfection.

Measurement of SARS-CoV-2-Specific Humoral and Cellular Immunity in Coronavirus Disease 2019 Convalescent Health Care Workers in Iraq

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) belongs to the Coronaviridae family which led to a global pandemic. However, available knowledge on adaptive immunity in convalescent individuals is limited. The present study was conducted on 191 convalescent coronavirus disease 2019 (COVID-19) health care workers (HCW); moreover, it evaluated the cell-mediated immunity of 122 recovered HCW and the level of anti-receptor binding domain (RBD) IgG antibodies of 181 recovered HCW. Cellular and humoral immune responses were identified over time from one to eight months post recovery with varying disease severity using MTT proliferation assay and enzyme-linked immunosorbent assay. Analysis of lymphocyte proliferation with S1 protein in mild-moderate and severe HCW revealed an insignificant difference with an increase in the maximum and third quartile (Q3) from one to eight months after COVID-19 recovery. Antibody levels in mild-moderate and severe recovered HCW were insignificantly different from post-COVID 19 recovery (P>0.05); in addition, the median, maximum, and Q3 values of anti-RBD IgG were close to each other over the time intervals from one to eight months post recovery. These data suggest that many convalescent HCW enrolled in this study were re-exposed to the virus without the development of symptoms indicating the role of cell-mediated and humoral immunity in preventing symptomatic reinfection. This study reveals that a robust immunity developed after mild, moderate, and severe COVID-19 that could last for several months post recovery.

The landscape of tumor cell states and ecosystems in diffuse large B cell lymphoma

Biological heterogeneity in diffuse large B cell lymphoma (DLBCL) is partly driven by cell-of-origin subtypes and associated genomic lesions, but also by diverse cell types and cell states in the tumor microenvironment (TME). However, dissecting these cell states and their clinical relevance at scale remains challenging. Here, we implemented EcoTyper, a machine-learning framework integrating transcriptome deconvolution and single-cell RNA sequencing, to characterize clinically relevant DLBCL cell states and ecosystems. Using this approach, we identified five cell states of malignant B cells that vary in prognostic associations and differentiation status. We also identified striking variation in cell states for 12 other lineages comprising the TME and forming cell state interactions in stereotyped ecosystems. While cell-of-origin subtypes have distinct TME composition, DLBCL ecosystems capture clinical heterogeneity within existing subtypes and extend beyond cell-of-origin and genotypic classes. These results resolve the DLBCL microenvironment at systems-level resolution and identify opportunities for therapeutic targeting (https://ecotyper.stanford.edu/lymphoma).

Functional Th1-oriented T follicular helper cells that infiltrate human breast cancer promote effective adaptive immunity

We previously demonstrated that tumor-infiltrating lymphocytes (TIL) in human breast cancer sometimes form organized tertiary lymphoid structures (TLS) characterized by CXCL13-producing T follicular helper (Tfh) cells. The present study found that CD4+ Tfh TIL, CD8+ TIL, and TIL-B, colocalizing in TLS, all express the CXCL13 receptor CXCR5. An ex vivo functional assay determined that only activated, functional Th1-oriented Tfh TIL (PD-1hiICOSint phenotype) provide help for immunoglobulin and IFN-γ production. A functional Tfh TIL presence signals an active TLS, characterized by humoral (immunoglobulins, Ki-67+ TIL-B in active germinal centers) and cytotoxic (GZMB+CD8+ and GZMB+CD68+ TIL plus Th1 gene expression) immune responses. Analysis of active versus inactive TLS in untreated patients revealed that the former are associated with positive clinical outcomes. TLS also contain functional T follicular regulatory (Tfr) TIL, which are characterized by a CD25+CXCR5+GARP+FOXP3+ phenotype and a demethylated FOXP3 gene. Functional Tfr inhibited functional Tfh activities via a glycoprotein A repetitions predominant (GARP)-associated TGF-β-dependent mechanism. The activity of tumor-associated TLS was dictated by the relative balance between functional Tfh TIL and functional Tfr TIL. These data provide mechanistic insight into TLS processes orchestrated by functional Th1-oriented Tfh TIL, including TIL-B and CD8+ TIL activation and immunological memory generation. Tfh TIL, regulated by functional Tfr TIL, are an expected key target of PD-1/PD-L1 blockade.

CD8 follicular T cells localize throughout the follicle during germinal center reactions and maintain cytolytic and helper properties

Follicular CXCR5+ PD-1+ CD8 T cells (CD8 Tfc) arise in multiple models of systemic autoimmunity yet their functional contribution to disease remains in debate. Here we define the follicular localization and functional interactions of CD8 Tfc with B cells during autoimmune disease. The absence of functional T regulatory cells in autoimmunity allows for CD8 Tfc development that then expands with lymphoproliferation. CD8 Tfc are identifiable within the lymph nodes and spleen during systemic autoimmunity, but not during tissue-restricted autoimmune disease. Autoimmune CD8 Tfc cells are polyfunctional, producing helper cytokines IL-21, IL-4, and IFNγ while maintaining cytolytic proteins CD107a, granzyme B, and TNF. During autoimmune disease, IL-2-KO CD8 T cells infiltrate the B cell follicle and germinal center, including the dark zone, and in vitro induce activation-induced cytidine deaminase in naïve B cells via IL-4 secretion. CD8 Tfc represent a unique CD8 T cell population with a diverse effector cytokine repertoire that can contribute to pathogenic autoimmune B cell response.

CXCR5+CD8+ T Cells Shape Antibody Responses In Vivo Following Protein Immunisation and Peripheral Viral Infection

Crosstalk between T and B cells is crucial for generating high-affinity, class-switched antibody responses. The roles of CD4⁺ T cells in this process have been well-characterised. In contrast, regulation of antibody responses by CD8⁺ T cells is significantly less defined. CD8⁺ T cells are principally recognised for eliciting cytotoxic responses in peripheral tissues and forming protective memory. However, recent findings have identified a novel population of effector CD8⁺ T cells that co-opt a differentiation program characteristic of CD4⁺ T follicular helper (Tfh) cells, upregulate the chemokine receptor CXCR5 and localise to B cell follicles. While it has been shown that CXCR5⁺CD8⁺ T cells mediate the removal of viral reservoirs in the context of follicular-trophic viral infections and maintain the response to chronic insults by virtue of progenitor/stem-like properties, it is not known if CXCR5⁺CD8⁺ T cells arise during acute peripheral challenges in the absence of follicular infection and whether they influence B cell responses in vivo in these settings. Using the ovalbumin-specific T cell receptor transgenic (OT-I) system in an adoptive transfer-immunisation/infection model, this study demonstrates that CXCR5⁺CD8⁺ T cells arise in response to protein immunisation and peripheral viral infection, displaying a follicular-homing phenotype, expression of cell surface molecules associated with Tfh cells and limited cytotoxic potential. Furthermore, studies assessing the B cell response in the presence of OT-I or Cxcr5^-/- OT-I cells revealed that CXCR5⁺CD8⁺ T cells shape the antibody response to protein immunisation and peripheral viral infection, promoting class switching to IgG2c in responding B cells. Overall, the results highlight a novel contribution of CD8⁺ T cells to antibody responses, expanding the functionality of the adaptive immune system.

CXCR5+CD8+ T cells: A Review of their Antibody Regulatory Functions and Clinical Correlations

CD8⁺ T cells have conventionally been studied in relationship to pathogen or tumor clearance. Recent reports have identified novel functions of CXCR5⁺CD8⁺ T cells that can home to lymphoid follicles, a key site of antibody production. In this review we provide an in-depth analysis of conflicting reports regarding the impact of CXCR5⁺CD8⁺ T cells on antibody production and examine the data supporting a role for antibody-enhancement (B cell "helper") and antibody-downregulation (antibody-suppressor) by CXCR5⁺CD8⁺ T cell subsets. CXCR5⁺CD8⁺ T cell molecular phenotypes are associated with CD8-mediated effector functions including distinct subsets that regulate antibody responses. Co-inhibitory molecule PD-1, among others, distinguish CXCR5⁺CD8⁺ T cell subsets. We also provide the first in-depth review of human CXCR5⁺CD8⁺ T cells in the context of clinical outcomes and discuss the potential utility of monitoring the quantity of peripheral blood or tissue infiltrating CXCR5⁺CD8⁺ T cells as a prognostic tool in multiple disease states.

The PI-3-Kinase P110α Catalytic Subunit of T Lymphocytes Modulates Collagen-Induced Arthritis

The phosphatidylinositol 3-kinase (PI3K) family of enzymes plays a determinant role in inflammation and autoimmune responses. However, the implication of the different isoforms of catalytic subunits in these processes is not clear. Rheumatoid arthritis (RA) is a chronic, systemic autoimmune inflammatory disease that entails innate and adaptive immune response elements in which PI3K is a potential hub for immune modulation. In a mouse transgenic model with T-cell-specific deletion of p110α catalytic chain (p110α-/-ΔT), we show the modulation of collagen-induced arthritis (CIA) by this isoform of PI3K. In established arthritis, p110α-/-ΔT mice show decreased prevalence of illness than their control siblings, higher IgG1 titers and lower levels of IL-6 in serum, together with decreased ex vivo Collagen II (CII)-induced proliferation, IL-17A secretion and proportion of naive T cells in the lymph nodes. In a pre-arthritis phase, at 13 days post-Ag, T-cell-specific deletion of p110α chain induced an increased, less pathogenic IgG1/IgG2a antibodies ratio; changes in the fraction of naive and effector CD4+ subpopulations; and an increased number of CXCR5+ T cells in the draining lymph nodes of the p110α-/-ΔT mice. Strikingly, T-cell blasts in vitro obtained from non-immunized p110α-/-ΔT mice showed an increased expression of CXCR5, CD44 and ICOS surface markers and defective ICOS-induced signaling towards Akt phosphorylation. These results, plus the accumulation of cells in the lymph nodes in the early phase of the process, could explain the diminished illness incidence and prevalence in the p110α-/-ΔT mice and suggests a modulation of CIA by the p110α catalytic chain of PI3K, opening new avenues of intervention in T-cell-directed therapies to autoimmune diseases.

Single-cell RNA sequencing of psoriatic skin identifies pathogenic Tc17 cell subsets and reveals distinctions between CD8+ T cells in autoimmunity and cancer

BACKGROUND

Psoriasis is an inflammatory, IL-17-driven skin disease in which autoantigen-induced CD8⁺ T cells have been identified as pathogenic drivers.

OBJECTIVE

Our study focused on comprehensively characterizing the phenotypic variation of CD8⁺ T cells in psoriatic lesions.

METHODS

We used single-cell RNA sequencing to compare CD8⁺ T-cell transcriptomic heterogeneity between psoriatic and healthy skin.

RESULTS

We identified 11 transcriptionally diverse CD8⁺ T-cell subsets in psoriatic and healthy skin. Among several inflammatory subsets enriched in psoriatic skin, we observed 2 Tc17 cell subsets that were metabolically divergent, were developmentally related, and expressed CXCL13, which we found to be a biomarker of psoriasis severity and which achieved comparable or greater accuracy than IL17A in a support vector machine classifier of psoriasis and healthy transcriptomes. Despite high coinhibitory receptor expression in the Tc17 cell clusters, a comparison of these cells with melanoma-infiltrating CD8⁺ T cells revealed upregulated cytokine, cytolytic, and metabolic transcriptional activity in the psoriatic cells that differed from an exhaustion program.

CONCLUSION

Using high-resolution single-cell profiling in tissue, we have uncovered the diverse landscape of CD8⁺ T cells in psoriatic and healthy skin, including 2 nonexhausted Tc17 cell subsets associated with disease severity.

Intratumoral CXCR5+CD8+T associates with favorable clinical outcomes and immunogenic contexture in gastric cancer

Studies that examined an association between CD8⁺T and prognosis in gastric cancer are inconsistent, and a distinct population of CXCR5⁺CD8⁺T associated with better overall survival has been reported among various malignancies. Here, we show that the abundance of intratumoral CXCR5⁺CD8⁺T cells is associated with better overall survival in patients with gastric cancer. Patients with TNM II + III gastric cancer with higher intratumoral CXCR5⁺CD8⁺T cell infiltration are more likely to benefit from adjuvant chemotherapy. Microsatellite-unstable and Epstein–Barr virus positive tumors are enriched with CXCR5⁺CD8⁺T cells. Gastric cancer infiltrating CXCR5⁺CD8⁺T cells represent a specific subtype of stem-like CD8⁺T with effector memory feature. Identification of the clinical significance and phenotype of gastric cancer infiltrating CXCR5⁺CD8⁺T provides a roadmap for patient stratification and trials of targeted therapies.

The prognostic value of tumor infiltrating lymphocytes in gastric cancer remains controversial. Here the authors show a consistent association between higher density of intratumoral CXCR5+CD8+ T cells and longer overall survival in four different cohorts of patients with gastric cancer.

T cell signaling and Treg dysfunction correlate to disease kinetics in IL-2Rα-KO autoimmune mice

IL-2Rα, in part, comprises the high affinity receptor for IL-2, a cytokine important in immune proliferation, activation, and regulation. IL-2Rα deficient mice (IL-2Rα-KO) develop systemic autoimmune disease and die from severe anemia between 18 and 80 days of age. These mice develop kinetically distinct autoimmune progression, with approximately a quarter dying by 21 days of age and half dying after 30 days. This research aims to define immune parameters and cytokine signaling that distinguish cohorts of IL-2Rα-KO mice that develop early- versus late-stage autoimmune disease. To investigate these differences, we evaluated complete blood counts (CBC), antibody binding of RBCs, T cell numbers and activation, hematopoietic progenitor changes, and signaling kinetics, during autoimmune hemolytic anemia (AIHA) and bone marrow failure. We identified several alterations that, when combined, correlate to disease kinetics. Early onset disease correlates with anti-RBC antibodies, lower hematocrit, and reduced IL-7 signaling. CD8 regulatory T cells (Tregs) have enhanced apoptosis in early disease. Further, early and late end stage disease, while largely similar, had several differences suggesting distinct mechanisms drive autoimmune disease kinetics. Therefore, IL-2Rα-KO disease pathology rates, driven by T cell signaling, promote effector T cell activation and expansion and Treg dysfunction.

A Comprehensive Review of Biological Agents for Lupus: Beyond Single Target

Systemic lupus erythematosus (SLE) is an autoimmune disease that involves multiple immune cells. Due to its complex pathogenesis, the effectiveness of traditional treatment methods is limited. Many patients have developed resistance to conventional treatment or are not sensitive to steroid and immunosuppressant therapy, and so emerging therapeutic antibodies have become an alternative and have been shown to work well in many patients with moderate and severe SLE. This review summarizes the biological agents that are in the preclinical and clinical trial study of SLE. In addition to the various monoclonal antibodies that have been studied for a long time, such as belimumab and rituximab, we focused on another treatment for SLE, bispecific antibodies (BsAbs) such as tibulizumab, which simultaneously targets multiple pathogenic cytokines or pathways. Although the application of BsAbs in cancer has been intensively studied, their application in autoimmune diseases is still in the infant stage. This unique combined mechanism of action may provide a novel therapeutic strategy for SLE.

Identification and validation of an excellent prognosis subtype of muscle-invasive bladder cancer patients with intratumoral CXCR5+ CD8+ T cell abundance

Bladder cancer is the ninth most frequent-diagnosed disease worldwide, bearing high morbidity and mortality rates. Studies have shown that a particular population of CXCR5⁺CD8⁺ T cells was associated with superior prognosis in various tumor types, and yet its role in muscle-invasive bladder cancer (MIBC) remains unclear. In this study, 662 MIBC patients from 3 cohorts (Zhongshan Hospital, n = 141; Shanghai Cancer Center, n = 108; The Cancer Genome Atlas, n = 403) were analyzed retrospectively. 11 fresh resected samples of MIBC were examined to characterize the phenotype of CXCR5⁺CD8⁺ T cells and 402 MIBC patients from TCGA were applied for bioinformatics analysis. It was explored that the abundance of intratumoral CXCR5⁺CD8⁺ T cells indicated superior overall survival and disease-free survival. Patients with a higher infiltration of CXCR5⁺CD8⁺ T cells in tumor tissue benefit more from adjuvant chemotherapy (ACT). Intratumoral CXCR5⁺CD8⁺ T cells displayed cytolytic and self-renewal features. Remarkably, CXCR5⁺CD8⁺ T cells were mainly presented in the basal and stromal-rich subtypes of MIBC and tumors with enriched CXCR5⁺CD8⁺ T cells showed limited FGFR3 signaling signature and activated immunotherapeutic and EGFR associated pathway. In conclusion, we identified an excellent prognosis and ACT sensitive subtype of MIBC with intratumoral CXCR5⁺CD8⁺ T cell abundance. Tumors with high density of CXCR5⁺CD8⁺ T cells possessed potential sensitivity to immunotherapy and EGFR-targeted therapy. CXCR5⁺CD8⁺ T cells provide a new potential biomarker as well as a therapeutic target in MIBC.

T follicular helper cells in germinal center B cell selection and lymphomagenesis

Germinal centers (GCs) are confined anatomic regions where rapidly proliferating B cells undergo somatic mutation and selection and eventual differentiation into memory B cells or long-lived plasma cells. GCs are also the origin of malignancy, namely follicular lymphoma (FL), GC B cell-diffuse large B cell lymphoma (GCB-DLBCL), and Burkitt lymphoma (BL). GC B cell lymphomas maintain their GC transcriptional signatures and sustain many features of the GC microenvironment, including CD4+ T follicular helper (Tfh) cells. Tfh cells are essential for the formation and maintenance of GCs, providing critical helper signals such as CD40L. Large-scale sequencing efforts have led to new insights about the tightly regulated selection mechanisms that are commonly targeted during GC B cell lymphomagenesis. For instance, HVEM, a frequently mutated surface molecule in GC-derived lymphomas, engages the inhibitory receptor BTLA on Tfh cells and loss of HVEM leads to exaggerated T cell help. Here, we review current understanding of how Tfh cells contribute to the selection of GC B cells, with a particular emphasis on how Tfh cell signals may contribute to lymphomagenesis. The possibility of targeting Tfh cells for the treatment of GC-derived lymphomas is discussed.

Inverse relationship between CD40L expression and cytolytic molecule expression by CD8+CXCR5+ T follicular cytotoxic cells in colorectal cancer

CXCR5⁺ CD8 T cells, sometimes termed T follicular cytotoxic (Tfc) cells, are characterized by high proinflammatory cytokine and cytolytic molecule expression and low exhaustion and checkpoint molecule expression. Additionally, Tfc cells could promote B cell responses and support Ig release. It is yet unclear how Tfc cells could help B cells when they have the potential to mediate cytotoxicity at the same time. In this study, we found that Tfc cells expressed significantly higher levels of CD40L than non-Tfc CD8 T cells. Interestingly, Tfc cells from colorectal cancer (CRC) patients presented significantly higher CD40L than Tfc cells from healthy controls in a manner that was associated with CRC stage. Coincubation of Tfc cells and autologous B cells resulted in higher CD40L expression in a time-dependent manner. Interestingly, activated Tfc cells, when incubated with B cells, presented rapid downregulation of perforin and granzyme B. In general, greater than 50% of tumor-infiltrating Tfc cells expressed CD40L. In addition, the level of CD40L in tumor-infiltrating Tfc cells was higher in stage IV CRC patients than in stage II and stage III CRC patients. Interestingly, the levels of perforin and granzyme B expression by tumor-infiltrating Tfc cells were inversely correlated with the level of CD40L expression by tumor-infiltrating Tfc cells. Overall, we demonstrated that an inverse association existed between CD40L and cytotoxic molecule expression in Tfc cells from CRC patients.

The elusive identity of CXCR5+ CD8 T cells in viral infection and autoimmunity: Cytotoxic, regulatory, or helper cells?

Our knowledge on the development and functions of CXCR5⁺ CD8 T cells is rudimentary when confronted to other extensively studied CD8 T cell subsets. A decade ago, it became apparent that CD8 T cells possess two additional and rather unexpected functional properties other than cytotoxicity, one involving what is known as B cell helper activity and the other involving suppression of self-reactive responses generally known as T cell regulation. Although these adaptive responses are well-known functions of CD4 T cells, they remain poorly understood in CD8 T cells. Thus far, three subsets of CXCR5⁺ CD8 T cells have been identified. The first subset of CXCR5⁺ CD8 T cells is present in chronic viral infections and is referred to as progenitors of exhausted T cells showing heightened proliferative and cytotoxic properties as compared to CXCR5^- CD8 T cells. The second subset of CXCR5⁺ CD8 T cells functions as regulatory T cells that inhibit CD4 T follicular helper (Tfh) humoral responses and the development of autoantibodies. The third subset of CXCR5⁺ CD8 T cells was identified in mice with mutations in immunoregulatory genes (i.e. FOXP3 and IL-2-deficient mice) and involves CD8 T cells with Tfh-like properties that promote humoral autoimmunity through interaction with B cells. This review summarizes the phenotype, function, and differentiation of CXCR5⁺ CD8 T cells.

Does B Cell Follicle Exclusion of CD8+ T Cells Make Lymph Nodes Sanctuaries of HIV Replication?

As we learn more about the HIV latent reservoir, we continue to discover that the viral reservoir is more complicated than just a pool of infected resting memory CD4+ T cells in peripheral blood. Evidence increasingly points to both certain tissues and certain types of cells as potential viral reservoirs. T follicular helper cells (T_FH) are prime targets of HIV infection-this creates a sanctuary for infected cells because CD8+ T cells generally do not enter lymph node follicles unless they express CXCR5, and are not as effective at killing infected CD4+ T cells as peripheral CD8+ T cells. In this review, we summarize the current state of research on T_FH cell infection in peripheral lymphoid tissues and focus on the question of whether CD8+ T cell exclusion from B cell follicles is responsible, at least in part, for establishing secondary lymphoid tissue B cell follicles as an anatomic site of HIV transcription and replication.