CD18 Is Required for Intestinal T Cell Responses at Multiple Immune Checkpoints

KMT2D regulates activation, localization, and integrin expression by T-cells

Individuals with Kabuki syndrome present with immunodeficiency; however, how pathogenic variants in the gene encoding the histone-modifying enzyme lysine methyltransferase 2D (KMT2D) lead to immune alterations remain poorly understood. Following up on our prior report of KMT2D-altered integrin expression in B-cells, we performed targeted analyses of KMT2D's influence on integrin expression in T-cells throughout development (thymocytes through peripheral T-cells) in murine cells with constitutive- and conditional-targeted Kmt2d deletion. Using high-throughput RNA-sequencing and flow cytometry, we reveal decreased expression (both at the transcriptional and translational levels) of a cluster of leukocyte-specific integrins, which perturb aspects of T-cell activation, maturation, adhesion/localization, and effector function. H3K4me3 ChIP-PCR suggests that these evolutionary similar integrins are under direct control of KMT2D. KMT2D loss also alters multiple downstream programming/signaling pathways, including integrin-based localization, which can influence T-cell populations. We further demonstrated that KMT2D deficiency is associated with the accumulation of murine CD8+ single-positive (SP) thymocytes and shifts in both human and murine peripheral T-cell populations, including the reduction of the CD4+ recent thymic emigrant (RTE) population. Together, these data show that the targeted loss of Kmt2d in the T-cell lineage recapitulates several distinct features of Kabuki syndrome-associated immune deficiency and implicates epigenetic mechanisms in the regulation of integrin signaling.

Identification and classification of distinct surface markers of T regulatory cells

Background

Regulatory T (Treg) cells have emerged as key players in the maintenance of immune homeostasis. Although significant progress has been made in recent years to define the Treg surface markers involved with or identifying their suppressive function, there remains much to be elucidated, and many questions persist. This study determined the expression of surface markers on human peripheral Treg cells and conventional T (Tconv) cells in a steady state and after activation to gain insight into their mechanism of action and more precisely characterize this regulatory population in humans.

Methods

To screen Treg and Tconv cells, peripheral blood mononuclear cells (PBMCs) were isolated from volunteers, stained with a commercially available lyophilized antibody array comprising 371 surface antigens, and analyzed by flow cytometry. To compare Treg cells with activated Tconv cells, PBMCs were stimulated with PMA and further stained similar to freshly isolated cells.

Results

Treg and Tconv cells were positive for 135 and 168 of the 371 antigens, respectively. Based on the frequency distribution, all of the most highly expressed markers identified were shared by both Treg and Tconv cells and participate in T cell activation, act as costimulatory and signaling molecules, or exhibit adhesion and migratory functions. Additionally, we identified several differences in marker expression between Treg and Tconv cells, with most found in the expression of co-stimulatory (ICOS, GITR, 4-1BB) and co-inhibitory (TIGIT, CTLA-4) molecules, as well as chemokine receptors (CXCR4, CXCR5, CCR4, CCR5, CCR7, CCR8, and CXCR7). Furthermore, post-activation expression of surface molecules identified molecules capable of discriminating Treg cells from activated Tconv cells (GITR, 4-1BB, TIGIT, CD120b, and CD39); however, almost all of these markers were also expressed in a small fraction of activated Tconv cells.

Conclusions

These results offer insight into the biology of Tregs and contribute to their accurate identification and characterization in variety of immunological diseases as well as physiological processes.

Leukocyte inflammatory phenotype and function in migraine patients compared with matched non-migraine volunteers: a pilot study

Background

Migraine is a neurological condition characterized by chronic inflammation. However, not much is known about the potential role of peripheral blood immune cells in the pathophysiology of migraine.

Methods

We investigated the status of peripheral blood immune cells of 15 adults with frequent episodic or chronic migraine recruited chronologically from a randomized clinical trial (RCT) on Nutrition for Migraine (NCCIH 5R01AT007813-05) and 15 non-migraine, healthy volunteers (control) matched by age, gender, and Body Mass Index (BMI).

Continuous variables were presented as means ± standard deviationas well as medians, and comparisons between patients and healthy volunteers were performed with non-parametric Wilcoxon signed rank tests. Statistical analysis was performed using Stata (StataCorp. 2019. Stata Statistical Software). Fluorescence-Activated Cell Sorting (FACS) data were processed using FlowJo software (Ashland, OR: Becton, Dickenson and Company; 2019).

Results

We observed that migraineurs had a significantly lower percentage of non-classical monocytes (CD14⁺CD16⁺⁺) in blood circulation, compared to the control group. In addition, Migraineurs also showed a significantly lower percentage of blood CD3⁺CD4⁺ helper T cells and CD4⁺CD25⁺ regulatory T cells, compared to controls. Differences in leukocyte surface markers between chronic migraine patients and their matched controls were more prominent than those between episodic migraine patients and their matched controls.

Conclusions

Our results suggest that migraine is associated with dysregulated peripheral immune homeostasis and that inflammation and autoimmunity may play a role in its pathophysiology.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-022-02781-4.

Not Just an Adhesion Molecule: LFA-1 Contact Tunes the T Lymphocyte Program

The α_Lβ₂ integrin LFA-1 is known to play a key role in T lymphocyte migration, which is necessary to mount a local immune response, and is also the main driver of autoimmune diseases. This migration-triggering signaling process in T cells is tightly regulated to permit an immune response that is appropriate to the local trigger, as well as to prevent deleterious tissue-damaging bystander effects. Emerging evidence shows that, in addition to prompting a diverse range of downstream signaling cascades, LFA-1 stimulation in T lymphocytes modulates gene-transcription programs, including genetic signatures of TGF-β and Notch pathways, with multifactorial biological outcomes. This review highlights recent findings and discusses molecular mechanisms by which LFA-1 signaling influence T lymphocyte differentiation into the effector subsets Th1, Th17, and induced regulatory T cells. We argue that LFA-1 contact with a cognate ligand, such as ICAM-1, independent of the immune synapse activates a late divergence in T cells' effector phenotypes, hence fine-tuning their functioning.

Impact of periodontal intervention on local inflammation, periodontitis, and HIV outcomes

OBJECTIVE

The aim of this study was to determine active periodontal disease status in HIV and to determine the impact of periodontal disease resolution on HIV status.

METHODS

In this longitudinal cohort study, 73 HIV-positive subjects received comprehensive dental care. AAP, CDC/AAP, and BGI case definitions determined periodontal classification. Likelihood and frequency of moderate/severe periodontal disease were assessed based on demographic variables. The influence of periodontal intervention was assessed at baseline, 12, and 24 months. IL-6 was measured in a subset of subjects.

RESULTS

Of the periodontal classifications, BGI demonstrated the highest percentage category improvement with the intervention (>50%). Moderate/severe periodontitis was positively associated with HIV regardless of race, smoking status, gender, income level, and age, and was associated with increased IL-6. At baseline, the majority of subjects had severe periodontal disease regardless of ART status. Subjects with suppressed viral load at baseline demonstrated a significant improvement in BGI classification (P = 0.026), increased CD4 counts (P = 0.027), and decreased IL-6 levels (P = 0.03).

CONCLUSIONS

Periodontal inflammation was prevalent regardless of ART status. In virologically suppressed subjects, the intervention decreased periodontitis with a concomitant IL-6 decrease and CD4 increase. These findings suggest a relationship between periodontal inflammation, oral microbial translocation, and HIV status.

Optimal T Cell Activation and B Cell Antibody Responses In Vivo Require the Interaction between Leukocyte Function-Associated Antigen-1 and Kindlin-3

Kindlin-3 is an important integrin regulator that is mutated in the rare genetic disorder, leukocyte adhesion deficiency type III, a disorder characterized by defective neutrophil trafficking and platelet function, leading to recurrent bacterial infections and bleeding. Kindlin-3 is also known to regulate T cell adhesion in vitro and trafficking in vivo, but whether the integrin/kindlin interaction regulates T or B cell activation in vivo is unclear. In this study, we used TTT/AAA β2-integrin knock-in (KI) mice and TCR-transgenic (OT-II) KI mice, in which the integrin/kindlin connection is disrupted, to investigate the role of the integrin/kindlin interaction in T cell activation. We show that basal T cell activation status in these animals in vivo is normal, but they display reduced T cell activation by wild-type Ag-loaded dendritic cells in vitro. In addition, T cell activation in vivo is reduced. We also show that basal Ab levels are normal in TTT/AAA β2-integrin KI mice, but B cell numbers in lymph nodes and IgG and IgM production after immunization are reduced. In conclusion, we show that the integrin/kindlin interaction is required for trafficking of immune cells, as well as for T cell activation and B cell Ab responses in vivo. These results imply that the immunodeficiency found in leukocyte adhesion deficiency type III patients, in addition to being caused by defects in neutrophil function, may be due, in part, to defects in lymphocyte trafficking and activation.

T cell-extrinsic CD18 attenuates antigen-dependent CD4+ T cell activation in vivo

The β2 integrins (CD11/CD18) are heterodimeric leukocyte adhesion molecules expressed on hematopoietic cells. The role of T cell-intrinsic CD18 in trafficking of naive T cells to secondary lymphoid organs and in Ag-dependent T cell activation in vitro and in vivo has been well defined. However, the T cell-extrinsic role for CD18, including on APC, in contributing to T cell activation in vivo is less well understood. We examined the role for T cell-extrinsic CD18 in the activation of wild-type CD4(+) T cells in vivo through the adoptive transfer of DO11.10 Ag-specific CD4(+) T cells into CD18(-/-) mice. We found that T cell-extrinsic CD18 was required for attenuating OVA-induced T cell proliferation in peripheral lymph nodes (PLN). The increased proliferation of wild-type DO11.10 CD4(+) T cells in CD18(-/-) PLN was associated with a higher percentage of APC, and these APC demonstrated an increased activation profile and increased Ag uptake, in particular in F4/80(+) APC. Depletion of F4/80(+) cells both reduced and equalized Ag-dependent T cell proliferation in CD18(-/-) relative to littermate control PLN, demonstrating that these cells play a critical role in the enhanced T cell proliferation in CD18(-/-) mice. Consistently, CD11b blockade, which is expressed on F4/80(+) macrophages, enhanced the proliferation of DO11.10 CD4(+) T cells in CD18(+/-) PLN. Thus, in contrast to the T cell-intrinsic essential role for CD18 in T cell activation, T cell-extrinsic expression of CD18 attenuates Ag-dependent CD4(+) T cell activation in PLN in vivo.

Roles of T cell-associated L-selectin and β7 integrins during induction and regulation of chronic colitis

BACKGROUND

L-selectin (CD62L) and β(7) integrins are important for trafficking of naive T cells under steady-state conditions. The objectives of this study were to dissect the requirements for T cell-associated CD62L and β(7) integrins during initiation, progression, and regulation of chronic colitis.

METHODS

Using the T-cell transfer model, we compared colitogenic potential between T cells lacking one or both of these molecules with wild-type T cells. To assess trafficking of cells to the secondary lymphoid tissue and the gut, we performed co-homing experiments.

RESULTS

Adoptive transfer of wild-type, CD62L(-/-) or β(7)(-/-) single-deficient T cells induced moderate to severe disease with slightly different kinetics. However, transfer of CD62L(-/-) β(7)(-/-) double-deficient (DKO) T cells produced significantly attenuated gut inflammation, which correlated with fewer T cells and reduced levels of proinflammatory cytokines in the colon lamina propria. Our subsequent experiments established that lack of colitogenic potential of these cells was due to inability of DKO T cells to home to the secondary lymphoid tissue. Furthermore, homing of in vitro-generated effector DKO T cells to the inflamed intestine was significantly impaired. Lastly, DKO regulatory T cells were ineffective at suppressing colitis induced by wild-type T cells.

CONCLUSIONS

We established that T cells can use either CD62L(-/-) or β(7)(-/-) integrins to induce chronic colitis, but lack of both abrogates their colitogenic potential. Effector T cells critically rely on β(7) integrin during their recruitment to the inflamed intestinal mucosa. Finally, regulation of intestinal inflammation by regulatory T cells requires one or both of these adhesion molecules.

CD11a regulates effector CD8 T cell differentiation and central memory development in response to infection with Listeria monocytogenes

β2 (CD18) integrins with α-chains CD11a, -b, -c, and -d are important adhesion molecules necessary for leukocyte migration and cellular interactions. CD18 deficiency leads to recurrent bacterial infections and poor wound healing due to reduced migration of leukocytes to inflammatory sites. CD8 T cells also upregulate CD11a, CD11b, and CD11c upon activation. However, the role these molecules play for CD8 T cells in vivo is not known. To determine the function of individual β2 integrins, we examined CD8 T cell responses to Listeria monocytogenes infection in CD11a-, CD11b-, and CD11c-deficient mice. The absence of CD11b or CD11c had no effect on the generation of antigen-specific CD8 T cells. In contrast, the magnitude of the primary CD8 T cell response in CD11a-deficient mice was significantly reduced. Moreover, the response in CD11a(-/-) mice exhibited reduced differentiation of short-lived effector cells (KLRG1(hi) CD127(lo)), although cytokine and granzyme B production levels were unaffected. Notably, CD11a deficiency resulted in greatly enhanced generation of CD62L(+) central memory cells. Surprisingly, CD8 T cells lacking CD11a mounted a robust secondary response to infection. Taken together, these findings demonstrated that CD11a expression contributes to expansion and differentiation of primary CD8 T cells but may be dispensable for secondary responses to infection.

Role of LFA-1 in the activation and trafficking of T cells: implications in the induction of chronic colitis

INTRODUCTION

We have previously demonstrated that adoptive transfer of naïve CD4(+) T cells devoid of lymphocyte function-associated antigen-1-deficient (LFA-1; CD11a/CD18) into recombination activating gene-1 (RAG-1) deficient (RAG(-/-) ) mice fails to induce chronic colitis whereas transfer of wild type (WT) T-cells induces unrelenting and chronic disease.

METHODS

The objectives of this study were to assess the role of lymphocyte function-associated antigen-1 (LFA-1) in enteric antigen (EAg)-induced activation of T cells in vitro and in vivo and to define the importance of this integrin in promoting trafficking of T cells to the mesenteric lymph nodes (MLNs) and colon.

RESULTS

We found that EAg-pulsed dendritic cells (DCs) induced proliferation of LFA-1-deficient (CD11a(-/-) ) CD4(+) T cells that was very similar to that induced using WT T cells, suggesting that LFA-1 is not required for activation/proliferation of T cells in vitro. Coculture of WT or CD11a(-/-) T cells with EAg-pulsed DCs induced the generation of similar amounts of interferon-gamma, interleukin (IL)-4, and IL-10, whereas IL-17A production was reduced ≈ 2-fold in cocultures with CD11a(-/-) T cells. Short-term (20-22 hours) trafficking studies demonstrated that while both WT and CD11a(-/-) T cells migrated equally well into the spleen, liver, lungs, small intestine, cecum, and colon, trafficking of CD11a(-/-) T cells to the MLNs was reduced by 50% when compared to WT T cells. When the observation period was extended to 3-7 days posttransfer, we observed ≈ 2-3-fold more WT T cells within the MLNs and colon than CD11a(-/-) T cells, whereas T-cell proliferation (as measured by CFSE dilution) was comparable in both populations.

CONCLUSIONS

Taken together, our data suggest that LFA-1 is not required for EAg-induced activation of CD4(+) T cells in vitro or in vivo but is required for trafficking of T cells to the MLNs and homing of colitogenic effector cells to the colon where they initiate chronic gut inflammation.

Targeting T-cell migration in inflammatory bowel disease

Crohn's disease and ulcerative colitis are chronic inflammatory disorders of the gastrointestinal tract and are collectively referred to as inflammatory bowel disease (IBD). IBD is a major cause of lifetime morbidity, has a severe impact on quality of life of patients (equivalent to that of rheumatoid arthritis, asthma, migraine or diabetes) and constitutes a substantial economic burden to the healthcare system. The introduction of anti-tumour necrosis factor (TNF) antibodies has dramatically improved the treatment of IBD, but approximately one-third of patients are nonresponders and another 30-50% will eventually lose the therapeutic effect or become intolerant to these antibodies. Thus, there is an urgent and unmet need for new therapies. The aetiologies of the different forms of IBD have not been fully elucidated but there is strong evidence implicating T cells and T-cell migration to the gut in initiating and perpetuating the intestinal inflammatory process and tissue destruction. In recent years, progress in basic science has shed light on the mechanisms regulating T-cell migration to the gut and new therapeutics targeting these pathways have been developed. It is interesting that some of the factors directing the localization of T cells to the gut have been shown to be relatively organ specific, potentially enabling new T-cell-targeted treatments to demonstrate improved safety whilst preserving therapeutic efficacy. Here, fundamental aspects of the gut immune system, the generation of tissue-tropic effector T cells and the mechanisms of T-cell trafficking to the gut mucosa will be reviewed. In addition, the role of these processes in IBD and how they have been exploited for the development of novel therapies for IBD will be discussed.

CD18 is required for optimal lymphopenia-induced proliferation of mouse T cells

Lymphocyte numbers are tightly regulated; with acute lymphopenia, T cell numbers are reestablished through lymphopenia-induced proliferation. In contrast to the costimulation requirements of antigen-driven proliferation, a number of costimulatory molecules are not required for lymphopenia-induced proliferation. However, the requirement for major histocompatibility complex (MHC)-T cell receptor (TCR) interactions and the enhanced lymphopenia-induced proliferation in T cells with higher TCR affinity argue for a role for surface molecules that contribute to efficient MHC-TCR interactions, in particular adhesion molecules. CD18 is an integrin that contributes to the activation of peripheral and intestinal T cells through adhesive and costimulatory mechanisms. We found that CD18 is required for optimal polyclonal and monoclonal CD4+ T cell lymphopenia-induced proliferation in recombination-activating gene 1-deficient (RAG-1-/-) mice; this requirement persisted over time. Uniquely, the dependency on CD18 in CD4+ T cells is in the rapid proliferation in RAG-1-/- recipients and in the slow homeostatic proliferation in irradiated Balb/c recipients. Consistent with the proposed role for intestinal microbiota in lymphopenia-induced rapid proliferation in RAG-/- mice, we observed a significant reduction in rapid proliferation upon treatment of mice with antibiotics; however, the dependency on CD18 for optimal lymphopenia-induced proliferation persisted. Moreover, the dependency for CD18 is maintained over a wide range of numbers of initially transferred T cells, including a low number of initially transferred T cells, when the drive for proliferation is very strong and proliferation is more rapid. Overall, these data argue for an essential and broad role for CD18 in lymphopenia-induced proliferation.

T-cell homing to the gut mucosa: general concepts and methodological considerations

Effector/memory T cells can migrate to most extra-lymphoid tissues in the body. However, migration to the intestinal mucosa requires the expression of very specific homing receptors on T cells, integrin α4β7 and chemokine receptor CCR9. These receptors are induced by all-trans retinoic acid (RA), a vitamin A metabolite that is specifically synthesized by gut-associated dendritic cells (DC), but not by extra-intestinal DC. Here we summarize some general concepts on T cell homing with an emphasis on the gut mucosa. We also discuss experimental strategies to generate gut-homing T cells in vivo and in vitro and the techniques to track gut-homing T cells.

Beta2 integrins separate graft-versus-host disease and graft-versus-leukemia effects

Graft-versus-host disease (GVHD) remains a major cause of morbidity and mortality in allogeneic hematopoietic stem cell transplantation. Migration of donor-derived T cells into GVHD target organs plays an essential role in the development of GVHD. beta2 integrins are critically important for leukocyte extravasation through vascular endothelia and for T-cell activation. We asked whether CD18-deficient T cells would induce less GVHD while sparing the graft-versus-leukemia (GVL) effect. In murine allogeneic bone marrow transplantation models, we found that recipients of CD18-/- donor T cells had significantly less GVHD morbidity and mortality compared with recipients of wild-type (WT) donor T cells. Analysis of alloreactivity showed that CD18-/- and WT T cells had comparable activation, expansion, and cytokine production in vivo. Reduced GVHD was associated with a significant decrease in donor T-cell infiltration of recipient intestine and with an overall decrease in pathologic scores in intestine and liver. Finally, we found that the in vivo GVL effect of CD18-/- donor T cells was largely preserved, because mortality of the recipients who received transplants of CD18-/- T cells plus tumor cells was greatly delayed or prevented. Our data suggest that strategies to target beta2 integrin have clinical potential to alleviate or prevent GVHD while sparing GVL activity.