Intraepithelial Lymphocytes of the Intestine.

The intestinal epithelium, which segregates the highly stimulatory lumen from the underlying tissue, harbors one of the largest lymphocyte populations in the body, intestinal intraepithelial lymphocytes (IELs). IELs must balance tolerance, resistance, and tissue protection to maintain epithelial homeostasis and barrier integrity. This review discusses the ontogeny, environmental imprinting, T cell receptor (TCR) repertoire, and function of intestinal IELs. Despite distinct developmental pathways, IEL subsets share core traits including an epithelium-adapted profile, innate-like properties, cytotoxic potential, and limited TCR diversity. IELs also receive important developmental and functional cues through interactions with epithelial cells, microbiota, and dietary components. The restricted TCR diversity of IELs suggests that a limited set of intestinal antigens drives IEL responses, with potential functional consequences. Finally, IELs play a key role in promoting homeostatic immunity and epithelial barrier integrity but can become pathogenic upon dysregulation. Therefore, IELs represent intriguing but underexamined therapeutic targets for inflammatory diseases and cancer.

TGF-ß Regulation of T Cells.

Transforming growth factor ß (TGF-ß) is a key cytokine regulating the development, activation, proliferation, differentiation, and death of T cells. In CD4+ T cells, TGF-ß maintains the quiescence and controls the activation of naive T cells. While inhibiting the differentiation and function of Th1 and Th2 cells, TGF-ß promotes the differentiation of Th17 and Th9 cells. TGF-ß is required for the induction of Foxp3 in naive T cells and the development of regulatory T cells. TGF-ß is crucial in the differentiation of tissue-resident memory CD8+ T cells and their retention in the tissue, whereas it suppresses effector T cell function. In addition, TGF-ß also regulates the generation or function of natural killer T cells, γδ T cells, innate lymphoid cells, and gut intraepithelial lymphocytes. Here I highlight the major findings and recent advances in our understanding of TGF-ß regulation of T cells and provide a personal perspective of the field.

Chronic Inflammation Permanently Reshapes Tissue-Resident Immunity in Celiac Disease.

Tissue-resident lymphocytes play a key role in immune surveillance, but it remains unclear how these inherently stable cell populations respond to chronic inflammation. In the setting of celiac disease (CeD), where exposure to dietary antigen can be controlled, gluten-induced inflammation triggered a profound depletion of naturally occurring Vγ4+/Vδ1+ intraepithelial lymphocytes (IELs) with innate cytolytic properties and specificity for the butyrophilin-like (BTNL) molecules BTNL3/BTNL8. Creation of a new niche with reduced expression of BTNL8 and loss of Vγ4+/Vδ1+ IELs was accompanied by the expansion of gluten-sensitive, interferon-γ-producing Vδ1+ IELs bearing T cell receptors (TCRs) with a shared non-germline-encoded motif that failed to recognize BTNL3/BTNL8. Exclusion of dietary gluten restored BTNL8 expression but was insufficient to reconstitute the physiological Vγ4+/Vδ1+ subset among TCRγδ+ IELs. Collectively, these data show that chronic inflammation permanently reconfigures the tissue-resident TCRγδ+ IEL compartment in CeD. VIDEO ABSTRACT.

T Cell Receptor Is Required for Differentiation, but Not Maintenance, of Intestinal CD4+ Intraepithelial Lymphocytes.

The gut epithelium is populated by intraepithelial lymphocytes (IELs), a heterogeneous T cell population with cytotoxic and regulatory properties, which can be acquired at the epithelial layer. However, the role of T cell receptor (TCR) in this process remains unclear. Single-cell transcriptomic analyses revealed distinct clonal expansions between cell states, with CD4+CD8αα+ IELs being one of the least diverse populations. Conditional deletion of TCR on differentiating CD4+ T cells or of major histocompatibility complex (MHC) class II on intestinal epithelial cells prevented CD4+CD8αα+ IEL differentiation. However, TCR ablation on differentiated CD4+CD8αα+ IELs or long-term cognate antigen withdraw did not affect their maintenance. TCR re-engagement of antigen-specific CD4+CD8αα+ IELs by Listeria monocytogenes did not alter their state but correlated with reduced bacterial invasion. Thus, local antigen recognition is an essential signal for differentiation of CD4+ T cells at the epithelium, yet differentiated IELs are able to preserve an effector program in the absence of TCR signaling.

Opportunities for Improving Biopsy and Non-Biopsy-Based Diagnosis of Celiac Disease.

The accumulating data regarding a non-biopsy diagnosis of celiac disease has led to its adoption in certain scenarios, although debate on whether and when to use non-biopsy criteria in clinical practice is ongoing. Despite the growing popularity and evidence basis for a biopsy-free approach to diagnosis in the context of highly elevated serologies, there will continue to be a role for a biopsy in some groups. This review summarizes the current evidence supporting a non-biopsy approach and arguments supporting continued reliance on biopsy, and focuses on opportunities to improve both approaches.

Advances in Nonresponsive and Refractory Celiac Disease.

Nonresponsive celiac disease (CeD) is relatively common. It is generally attributed to persistent gluten exposure and resolves after correction of diet errors. However, other complications of CeD and disorders clinically mimicking CeD need to be excluded. Novel therapies are being evaluated to facilitate mucosal recovery, which might benefit patients with nonresponsive CeD. Refractory CeD (RCeD) is rare and is divided into 2 types. The etiology of type I RCeD is unclear. A switch to gluten-independent autoimmunity is suspected in some patients. In contrast, type II RCeD represents a low-grade intraepithelial lymphoma. Type I RCeD remains a diagnosis of exclusion, requiring ruling out gluten intake and other nonmalignant causes of villous atrophy. Diagnosis of type II RCeD relies on the demonstration of a clonal population of neoplastic intraepithelial lymphocytes with an atypical immunophenotype. Type I RCeD and type II RCeD generally respond to open-capsule budesonide, but the latter has a dismal prognosis due to severe malnutrition and frequent progression to enteropathy-associated T-cell lymphoma; more efficient therapy is needed.

Activation of mucosal insulin receptor exacerbates intestinal inflammation by promoting tissue resident memory T cells differentiation through EZH2.

BACKGROUND: Inflammatory Bowel Diseases (IBD), an autoimmune disease characterised by abnormal intestinal immunity, are related to vital morbidity around the world. However, therapeutic agents for IBD have not achieved desired benefit. Exploring new therapeutic targets for IBD, especially based on its abnormally intestinal immunity, could alleviate the flare-up and worsening of IBD. Tissue resident memory T cells (TRM) are core of multiple autoimmune diseases, including IBD. However, the mechanism of TRM differentiation remains to be investigated. METHODS: The alterations in mRNA and lncRNA profile of intestinal intraepithelial lymphocytes (IELs), the largest component of intestinal TRM, were analyzed in DSS-induced chronic colitis. Based on it, we examined the function of rectal insulin instillation in a dextran sodium sulfate (DSS) induced chronic colitis. Furthermore, we investigated the downstream-target of the insulin pathway-EZH2 and the crucial role of EZH2 in intestinal tissue resident memory T cell differentiation by utilizing EZH2fl/flCD4cre mice. RESULTS: Insulin receptor (INSR) expression was found to be significantly reduced. Activation of mucosal insulin pathway by rectal insulin instillation exacerbated colitis by disrupting IELs subgroups and up-regulating TNF-ɑ and IL-17 expression. Rectal insulin instillation promoted EZH2 expression and EZH2 inhibition alleviated chronic colitis. EZH2fl/flCD4cre mice restored the normal IEL subgroups and suppressed TNF-ɑ and IL-17 expression, exhibiting alleviated colitis. IELs from EZH2fl/flCD4cre mice exhibit significant changes in TRM related phenotype. CD4+TRM was significantly increased in chronic colitis and decreased in EZH2fl/flCD4cre mice. CONCLUSION: Insulin receptor of intestinal mucosal T-cells could promote intestinal TRM differentiation via EZH2. Our discoveries suggest that therapies targeting colonic INSR and EZH2 could be potential treatment for IBD based on its regulatory effects on TRM. Insulin receptor inhibitors rather than insulin should be applied during colitis-active phase. In addition, EZH2 shows to be a downstream signal of the insulin pathway and EZH2 inhibitor could alleviating intestinal inflammation. However, the critical role of EZH2 in TRM differentiation restricts the anti-tumor effects of EZH2 inhibitor in vivo.

Interferon regulatory factor-2 is required for the establishment of the gut intraepithelial T-cell compartment.

CD8αα+ intestinal intraepithelial lymphocytes (iIELs) are known for their unique role in keeping the integrity of the intestinal epithelial barrier, but factors affecting the development of these cells have not been thoroughly understood. Here, we found that the transcriptional regulator interferon regulatory factor-2 (IRF-2) plays a cell-intrinsic, indispensable role in establishing iIEL populations. CD8αα+, but not CD8αß+, iIELs bearing TCRαß or TCRγδ were severely reduced in numbers in mice lacking this factor (Irf2-/- mice). Moreover, the majority of residual CD8αα+TCRαß+ iIELs in these mice was immature as judged from their Thy1.2high phenotype and inefficient T-bet expression. Thymic IEL precursors isolated from Irf2-/- mice failed to efficiently generate CD8αα+TCRαß+ and TCRγδ+ IELs upon transfer in vivo and CD8αα+TCRαß+ cells in response to IL-15 in vitro. Double mutant mice lacking both interleukin-15 (IL-15) and IRF-2 showed an even more severe iIEL defect than in mice lacking IL-15 alone. Upon increasing agonistic TCR signal strength through OT-II TCR transgenesis, CD8αα+TCRαß+ iIELs became more abundant but remained immature on the Irf2-/- background. Our current observations, thus, revealed the unique bimodal role that IRF-2 plays in promoting not only generation of IEL progenitors in the thymus but also maturation of iIELs in the periphery in IL-15-dependent and -independent manners.

CD4+CD8αα+ is the dominant phenotype of intraepithelial lymphocytes and regulated by ThPOK and Runx3 in Oral lichen planus.

BACKGROUND: Oral lichen planus (OLP) is a common T cell-mediated oral mucosal immune inflammatory disease. Intraepithelial lymphocytes (IELs) are a unique subset of T cells that play an important role in regulating immune response. This study aims to investigate the phenotype and the differentiation mechanism of IELs in OLP. METHODS: The expression of CD4, CD8α, CD8ß, T-helper-inducing POZ/Krueppel-like factor (ThPOK), and RUNX family transcription factor 3 (Runx3) in the epithelium and peripheral blood mononuclear cells (PBMCs) of OLP was determined by immunofluorescence and immunohistochemistry. Then, the correlations among them were analyzed. Naïve CD4+ T cells were sorted from blood of OLP patients and stimulated with retinoic acid (RA) and transforming growth factor-ß1 (TGF-ß1). Then the expression of CD4, CD8α, CD8ß, ThPOK, and Runx3 was investigated by immunocytochemistry. RESULTS: CD8α expression and CD8αα+ cells were upregulated in the epithelium of OLP, whereas they were downregulated in PBMCs of OLP. CD8ß was not expressed in the epithelium of OLP. CD4, CD8α, and Runx3 expression and CD4+CD8α+ cells were increased, whereas ThPOK expression was decreased in the epithelium of OLP. CD8α expression was positively correlated with Runx3 expression, whereas ThPOK expression was negatively correlated with Runx3 expression. After RA and TGF-ß1 stimulation, CD8α and Runx3 expression was upregulated, and ThPOK expression was downregulated in naïve CD4+ T cells. CONCLUSION: CD4+CD8αα+ IELs may be the dominant phenotype of IELs in OLP, and the differentiation of CD4+CD8αα+ IELs in OLP is negatively regulated by ThPOK and positively regulated by Runx3.

Single-cell TCR repertoire analysis reveals highly polyclonal composition of human intraepithelial CD8+ αß T lymphocytes in untreated celiac disease.

We compared the αß T-cell receptor repertoires of CD8+ αß intraepithelial lymphocytes from celiac disease patients and healthy subjects by single-cell sequencing. We demonstrate that the repertoires of untreated celiac disease patients were more polyclonal and more diverse than what was observed in both treated patients and healthy subjects.

Interleukin-6 absence triggers intestinal microbiota dysbiosis and mucosal immunity in mice.

Interleukin-6 (IL-6) in mucosal immune cells is involved in post-injury intestinal regeneration, inflammation responses, and gastric homeostasis. However, the interaction between IL-6 and the dynamic balance of gut microbiota (GM) remains unexplored. Intestinal pathology was assessed by hematoxylin and eosin and periodic acid-Schiff staining in wild-type (WT) and IL-6 gene knockout (KO) C57BL/6J mice. GM profiles were established via high-throughput sequencing of the fecal bacterial 16S rRNA gene. Intestinal α- and ß-defensins were measured by quantitative real-time PCR; further, flow cytometry was performed to analyze isolated intraepithelial lymphocytes (IELs). Compared with the WT, IL-6 KO did not obviously change gut structures, but significantly reduced GM diversity, resulting in reduced metabolic pathways with decreased gram-positive but elevated gram-negative bacteria. More taxa alterations included differences at the phyla (e.g., increased Verrucomicrobia and decreased Firmicutes) and genera (e.g., increased Akkermansia and decreased Lactobacillus) levels. Absence of IL-6 also significantly increased intestinal expression of defensins α3 and α4 (Defa3 and Defa4) and the percentage of natural TCRγδ+ IELs, providing a molecular basis for triggering mucosal immune response. Therefore, IL-6 loss remodels GM composition and alters IEL maintenance, identifying IL-6 as a crucial cytokine for GM dysbiosis and mucosal immunity.

Modulation of lymphocyte subpopulations in the small intestine of mice treated with probiotic bacterial strains and infected with Trichinella spiralis.

AIMS: To study the local intestinal lymphocyte immunity in mice with trichinellosis affected by probiotic bacteria. METHODS AND RESULTS: Enterococcus faecium CCM8558, Enterococcus durans ED26E/7, Limosilactobacillus fermentum CCM7421 and Lactiplantibacillus plantarum 17 L/1 were administered daily (109  CFU ml-1 ) and mice were infected with Trichinella spiralis (400 larvae) on the 7th day of treatment. T. spiralis infection significantly inhibited lymphocyte subpopulations from 5 to 25 days postinfection (dpi). L. fermentum CCM7421 and L. plantarum 17 L/1 restored the CD4+ T cell numbers in the epithelium and lamina propria at the control level from 11 dpi. All strains stimulated the CD8+ T cells numbers in infected mice, which were restored in the lamina propria on 11 dpi and in the epithelium only on 32 dpi. B cells (CD19+ ) inhibition after T. spiralis infection was not affected by treatment till 25 dpi. CONCLUSIONS: The strain-specific immunomodulatory effect of tested bacteria was confirmed. L. fermentum CCM7421 and L. plantarum 17 L/1 showed the greatest immunomodulatory potential on CD4+ and CD8+ T lymphocytes in trichinellosis. E. faecium CCM8558 and E. durans ED26E/7 activated only CD8+ T cells in the lamina propria. SIGNIFICANCE AND IMPACT OF THE STUDY: Positive modulation of the gut lymphocyte immunity in T. spiralis infection with bacterial strains showed their beneficial effect with the host's antiparasitic defence.

The molecular basis and cellular effects of distinct CD103 expression on CD4 and CD8 T cells.

Integrin CD103 mediates the adhesion and tissue retention of T cells by binding to E-cadherin which is abundant on epithelial cells. Notably, CD103 is highly expressed on CD8 T cells but conspicuously absent on most CD4 T cells. The mechanism controlling such lineage-specific expression of CD103 remains unclear. Using a series of genetically engineered mouse models, here, we demonstrate that the regulatory mechanism of CD103 expression is distinct between CD4 and CD8 T cells, and that the transcription factor Runx3 plays an important but not an essential role in this process. We further found that the availability of integrin ß7 which heterodimerizes with CD103 was necessary but also constrained the surface expression of CD103. Notably, the forced surface expression of CD103 did not significantly alter the thymic development of conventional T cells but severely impaired the generation of MHC-II-restricted TCR transgenic T cells, revealing previously unappreciated aspects of CD103 in the selection and maturation of CD4 T cells. Unlike its effect on CD4 T cell development, however, CD103 overexpression did not significantly affect CD4 T cells in peripheral tissues. Moreover, the frequency and number of CD4 T cells in the small intestine epithelium did not increase even though E-cadherin is highly expressed in this tissue. Collectively, these results suggest that most mature CD4 T cells are refractory to the effects of CD103 expression, and that they presumably utilize CD103-independent pathways to control their tissue retention and residency.

Dihydromyricetin Attenuates High-Intensity Exercise-Induced Intestinal Barrier Dysfunction Associated with the Modulation of the Phenotype of Intestinal Intraepithelial Lymphocytes.

BACKGROUND: Exercise-induced gastrointestinal syndrome (GIS) has symptoms commonly induced by strenuous sports. The study aimed to determine the effect of dihydromyricetin (DHM) administration on high-intensity exercise (HIE)-induced intestinal barrier dysfunction and the underlying mechanism involved with intestinal intraepithelial lymphocytes (IELs). METHODS: The HIE model was established with male C57BL/6 mice using a motorized treadmill for 2 weeks, and DHM was given once a day by oral gavage. After being sacrificed, the small intestines of the mice were removed immediately. RESULTS: We found that DHM administration significantly suppressed HIE-induced intestinal inflammation, improved intestinal barrier integrity, and inhibited a HIE-induced increase in the number of IELs and the frequency of CD8αα+ IELs. Meanwhile, several markers associated with the activation, gut homing and immune functions of CD8αα+ IELs were regulated by DHM. Mechanistically, luciferase reporter assay and molecular docking assay showed DHM could activate the aryl hydrocarbon receptor (AhR). CONCLUSIONS: These data indicate that DHM exerts a preventive effect against HIE-induced intestinal barrier dysfunction, which is associated with the modulation of the quantity and phenotype of IELs in the small intestine. The findings provide a foundation to identify novel preventive strategies based on DHM supplementation for HIE-induced GIS.

Intestinal Intraepithelial Lymphocytes: Sentinels of the Mucosal Barrier.

Intestinal intraepithelial lymphocytes (IELs) are a large and diverse population of lymphoid cells that reside between the intestinal epithelial cells (IECs) that form the intestinal mucosal barrier. Although IEL biology has traditionally focused on T cells, recent studies have identified several subsets of T cell receptor (TCR)-negative IELs with intriguing properties. New insight into the development, homeostasis, and functions of distinct IEL subsets has recently been provided. Additional studies have revealed intricate interactions between different IEL subsets, reciprocal interactions between IELs and IECs, and communication of IELs with immune cells that reside outside the intestinal epithelium. We review here sentinel functions of IELs in the maintenance of the mucosal barrier integrity, as well as how dysregulated IEL responses can contribute to pathology.

Diagnostic and therapeutic challenge of unclassifiable enteropathies with increased intraepithelial CD103+ CD8+ T lymphocytes: a single center case series.

OBJECTIVES: Chronic diarrhea, villous atrophy and/or increased intraepithelial T-lymphocytes (IEL) occur in many inflammatory disorders including celiac disease (CD). However, a definite diagnosis is difficult to make in some patients despite an extensive diagnostic work-up. Clinical outcomes and histological phenotypes of such patients we refer to as unclassifiable enteropathy (UEP) remain unclear. MATERIAL AND METHODS: We performed a retrospective single-center analysis of patients with chronic diarrhea, weight loss and increased IEL. Patients with defined etiologies including infections, CD, drugs, immunodeficiencies or neoplasms were excluded. Clinical and histologic/immunophenotypic parameters were analyzed. RESULTS: Nine patients with UEP were identified. Small intestinal damage ranged from minor villous abnormalities to complete atrophy while all patients displayed high numbers of CD103+ CD8+ IELs. In contrast to CD, these CD8+ T cells were not confined to the surface epithelium, but also infiltrated the crypts. Additional histological features included apoptotic crypt epithelial cells and mixed inflammatory infiltrates in the tunica propria. Involvement of other segments of the gastrointestinal tract was observed in 7/9 patients. A clonal intestinal T-cell lymphoproliferative disorder developed in 2 patients, one of which had a fatal disease course. The majority of patients responded to corticosteroids, while response to immunosuppressive medications yielded heterogeneous results. CONCLUSIONS: We report a patient population with 'difficult-to-classify' enteropathies characterized by various degrees of villous atrophy and strongly increased intraepithelial CD103+ CD8+ T cells in the small intestine which harbor an increased risk for T-cell lymphoproliferative disorders. Clinical course, histology, and response to immunosuppressive therapy all suggest an autoimmune pathogenesis.

Dynamic Imaging of IEL-IEC Co-Cultures Allows for Quantification of CD103-Dependent T Cell Migration.

Intraepithelial lymphocytes (IEL) are widely distributed within the small intestinal epithelial cell (IEC) layer and represent one of the largest T cell pools of the body. While implicated in the pathogenesis of intestinal inflammation, detailed insight especially into the cellular cross-talk between IELs and IECs is largely missing in part due to lacking methodologies to monitor this interaction. To overcome this shortcoming, we employed and validated a murine IEL-IEC (organoids) ex vivo co-culture model system. Using livecell imaging we established a protocol to visualize and quantify the spatio-temporal migratory behavior of IELs within organoids over time. Applying this methodology, we found that IELs lacking CD103 (i.e., integrin alpha E, ITGAE) surface expression usually functioning as a retention receptor for IELs through binding to E-cadherin (CD324) expressing IECs displayed aberrant mobility and migration patterns. Specifically, CD103 deficiency affected the ability of IELs to migrate and reduced their speed during crawling within organoids. In summary, we report a new technology to monitor and quantitatively assess especially migratory characteristics of IELs communicating with IEC ex vivo. This approach is hence readily applicable to study the effects of targeted therapeutic interventions on IEL-IEC cross-talk.

[The role of intraepithelial lymphocytes in pathogenesis of small intestinal bacterial overgrowth syndrome]. / Rola limfocytów sródnablonkowych w patogenezie zespolu przerostu bakteryjnego jelita cienkiego.

Small intestinal bacterial overgrowth (SIBO) is a frequent cause of chronic abdominal complaints. So far, a lot information has been gathered on its pathogenesis but are still doubts that raise question why its causes chronic diarrhea in some and constipation in other patients. AIM: The aim of the study was to assess the number of endothelial lymphocytes (IELs) in the duodenal and ileum mucosa in patients with SIBO with dominant diarrhea (SIBO-D) and dominant constipation (SIBO-C). MATERIALS AND METHODS: The study was performed in 30 healthy patients (group I) and 40 patients with SIBO and diarrhoea (group II), and in 4o patients with constipation (group III). To diagnose SIBO the lactulose hydrogen breath test (LHBT) was performed. To determine the number of intraepithelial lymphocytes in duodenal and jejunal mucosa the histological assessment was performed using haematoxylin-eosin staining. Moreover, immunochistochemical method was used to assess the number of enterochromatoffin cells (EC, chromogranin A - LK-2H10) in these some parts of the gut. RESULTS: The results of LHBT were similar in group II and III - 75,6±18,1 ppm and 66,9±16,2 ppm(p>0,05). The number of IELs in duodenal mucosa in controls was 14,6±4,1/100 EN, in group II - 28,3±6,8/100 EN (p<0.01), and in group III - 23,0±9,9/100 EN (p<0,05), and similar differences were in jejunal mucosa. The number of EC in both parts of the gut was higher in SIBO compared to controls. Furthermore, in patients with SIBO-D the number of IELs in duodenum, as well as in jejunum, was positively correlated with the number of EC cells ( p<0,05, p=0,056, respectively). CONCLUSIONS: In patients with SIBO, particularly with SIBO-D, increased number of IELs I EC cells may be a cause of diverse abdominal symptoms.

CD8αα+ T cells show amoeboid shape and frequent morphological change in vitro, and localize to small intestinal intraepithelial region in vivo.

Intraepithelial lymphocytes (IELs) are very unique in the intestinal immune system. They include γδT cells and CD4-CD8-TCRαß+T cells (double negative: DNT), both of which are specific for the intestine, in addition to CD4+ and CD8+ T cells. IELs exist within the monolayer of the intestinal epithelial cells and dynamically move between lamina propria (LP) and intraepithelial (IE) region. The localization and movement patterns of IEL subsets and the regulatory factors have been unknown. Here, we developed a novel in vitro live imaging system and quantified the motility and morphological changes among subsets of IELs. We identified CD8αα as the key regulatory factor. IELs, especially γδ and DNT cells, showed amoeboid shape and frequent morphological change, while most T cells in MLN or SP showed round shape in vitro. TCR signal, IL-15, gut microbes, CCL25, and integrin αEß7 expression were non-essential for IEL movement in vitro. CD8αα+ cells showed higher motility and larger morphological changes than CD8αα- cells. Adoptive transferred CD8αα+CD4-IELs localized to IE region of recipient NSG mice, while CD8αα-CD4-IELs localized to the LP. Our results showed that the CD8αα/TL signal is essential for the localization of IELs to IE region in vivo. CD8αα/TL may be an effective target to increase the number of IELs, which protects against intestinal infection, allergy, tumorigenesis or inflammation.

Cytotoxic T cell depletion with increasing epithelial abnormality in women with benign breast disease.

PURPOSE: We quantified cytotoxic T cells in nonmalignant breast tissues from women with and without subsequent breast cancer to assess evidence of whether immunosurveillance may be suppressed prior to tumor development. METHODS: We used an age-matched set of breast tissues from women with benign breast disease (BBD) who subsequently developed breast cancer (BBD with later BC), women with BBD who remained cancer free (BBD cancer-free), and normal Komen Tissue Bank (KTB) tissue donors (KTB controls). We evaluated terminal duct lobular units (lobules) for degree of epithelial abnormality and density of dual-positive CD8/CD103 T cells, as CD103+ cells are thought to be a subset of CD8+ cytotoxic T cells located primarily in the intraepithelial compartment. RESULTS: In 10 sets of age-matched women, 256 breast lobules were studied: 85 in BBD women with later BC, 85 in BBD cancer-free women, and 86 in KTB donors. The majority of all lobules were histologically normal (N = 143, 56%), with 65 (25%) nonproliferative fibrocystic change, and 48 (19%) proliferative epithelial change (with or without atypia). In BBD women with later BC, median CD8+/CD103+ cell density was 39.6, 31.7, and 10.5 cells/mm2 (p = 0.002) for normal, nonproliferative, and proliferative lobules. In BBD cancer-free women, median CD8+/CD103+ cell density values were 46.7, 14.3, and 0 cells/mm2 (p = 0.004) respectively. In KTB donors, CD8+/CD103+ cell density was not significantly different across the lobule types (medians 0, 5.8, 10.7, p = 0.43). CONCLUSION: In women with BBD, breast lobules with increasing epithelial abnormality show significant decreases in cytotoxic T cells as measured by CD8/CD103 staining, suggesting that impaired immunosurveillance may be a component of the earliest stages of breast cancer development.