Human Intraepithelial Lymphocytes Research Articles

Intraepithelial lymphocytes in the pig intestine: T cell and innate lymphoid cell contributions to intestinal barrier immunity.

Intraepithelial lymphocytes (IELs) include T cells and innate lymphoid cells that are important mediators of intestinal immunity and barrier defense, yet most knowledge of IELs is derived from the study of humans and rodent models. Pigs are an important global food source and promising biomedical model, yet relatively little is known about IELs in the porcine intestine, especially during formative ages of intestinal development. Due to the biological significance of IELs, global importance of pig health, and potential of early life events to influence IELs, we collate current knowledge of porcine IEL functional and phenotypic maturation in the context of the developing intestinal tract and outline areas where further research is needed. Based on available findings, we formulate probable implications of IELs on intestinal and overall health outcomes and highlight key findings in relation to human IELs to emphasize potential applicability of pigs as a biomedical model for intestinal IEL research. Review of current literature suggests the study of porcine intestinal IELs as an exciting research frontier with dual application for betterment of animal and human health.

Osteopontin promotes survival of intestinal intraepithelial lymphocytes and protects against colitis

Abstract Intestinal intraepithelial lymphocytes (IEL) comprise a diverse population of cells that reside in the epithelium at the interface between the contents of the intestinal lumen and the sterile environment of the lamina propria. Because of this anatomical location, IEL are considered critical components of intestinal immune responses. Indeed, IEL are involved in many different immunological processes ranging from pathogen control to tissue stability. However, maintenance of IEL homeostasis is incompletely understood. In this report, we present evidence that osteopontin, a glycophosphoprotein with diverse roles in biomineralization, cell-mediated immunity, and inflammation, is important for maintaining normal levels of IEL. Mice in which the osteopontin gene (Spp-1) is disrupted present decreased levels of IEL subtypes, such as TCRαβ and TCRγδ IEL in the intestine, an effect not observed for lymphocytes in other immune compartments such as spleen or lamina propria, indicating an epithelium-specific effect. In vitro experiments show that mouse and human IEL survival is improved by culture with recombinant osteopontin. In vivo and in vitro IEL survival studies show that CD44, a ligand for osteopontin, is critical for the capacity of osteopontin to promote IEL survival. Adoptive transfer of total T cells (including Tregs) from wild type mice into Spp-1−/−Rag-2−/− mice results in the development of exacerbated intestinal inflammation, as compared with Rag-2−/− recipient mice. Further analyses show that osteopontin-deficiency results in decreased survival of Foxp3-expressing T cells. These findings support osteopontin’s critical role in IEL homeostasis and make it a potential target for curbing intestinal inflammation.

Human intraepithelial lymphocytes.

The location of intraepithelial lymphocytes (IEL) between epithelial cells, their effector memory, cytolytic and inflammatory phenotype positions them to kill infected epithelial cells and protect the intestine against pathogens. Human TCRαβ+CD8αβ+ IEL have the dual capacity to recognize modified self via natural killer (NK) receptors (autoreactivity) as well as foreign antigen via the T cell receptor (TCR), which is accomplished in mouse by two cell subsets, the naturally occurring TCRαβ+CD8αα+ and adaptively induced TCRαβ+CD8αβ+ IEL subsets, respectively. The private/oligoclonal nature of the TCR repertoire of both human and mouse IEL suggests local environmental factors dictate the specificity of IEL responses. The line between sensing of foreign antigens and autoreactivity is blurred for IEL in celiac disease, where recognition of stress ligands by induced activating NK receptors in conjunction with inflammatory signals such as IL-15 can result in low-affinity TCR/non-cognate antigen and NK receptor/stress ligand interactions triggering destruction of intestinal epithelial cells.

Intraepithelial lymphocytes in celiac disease immunopathology

Celiac disease is a T cell-mediated immune disorder induced by dietary gluten that is characterized by the development of an inflammatory anti-gluten CD4 T cell response, anti-gluten antibodies, and autoantibodies against tissue transglutaminase 2 and the activation of intraepithelial lymphocytes (IELs) leading to the destruction of the intestinal epithelium. Intraepithelial lymphocytes represent a heterogeneous population of T cells composed mainly of cytotoxic CD8 T cells residing within the epithelial layer, whose main role is to maintain the integrity of the epithelium by eliminating infected cells and promoting epithelial repair. Dysregulated activation of IELs is a hallmark of CD and is critically involved in epithelial cell destruction and the subsequent development of villous atrophy. In this review, we compare and contrast the phenotype and function of human and mouse small intestinal IELs under physiological conditions. Furthermore, we discuss how conditions of epithelial distress associated with overexpression of IL-15 and non-classical MHC class I molecules induce cytotoxic IELs to become licensed killer cells that upregulate activating NKG2D and CD94/NKG2C natural killer receptors, acquiring lymphokine killer activity. Pathways leading to dysregulated IEL activation could eventually be targeted to prevent villous atrophy and treat patients who respond poorly to gluten-free diet.

IL-15 triggers an antiapoptotic pathway in human intraepithelial lymphocytes that is a potential new target in celiac disease–associated inflammation and lymphomagenesis

Enteropathy-associated T cell lymphoma is a severe complication of celiac disease (CD). One mechanism suggested to underlie its development is chronic exposure of intraepithelial lymphocytes (IELs) to potent antiapoptotic signals initiated by IL-15, a cytokine overexpressed in the enterocytes of individuals with CD. However, the signaling pathway by which IL-15 transmits these antiapoptotic signals has not been firmly established. Here we show that the survival signals delivered by IL-15 to freshly isolated human IELs and to human IEL cell lines derived from CD patients with type II refractory CD (RCDII) - a clinicopathological entity considered an intermediary step between CD and enteropathy-associated T cell lymphoma - depend on the antiapoptotic factors Bcl-2 and/or Bcl-xL. The signals also required IL-15Rbeta, Jak3, and STAT5, but were independent of PI3K, ERK, and STAT3. Consistent with these data, IELs from patients with active CD and RCDII contained increased amounts of Bcl-xL, phospho-Jak3, and phospho-STAT5. Furthermore, incubation of patient duodenal biopsies with a fully humanized human IL-15-specific Ab effectively blocked Jak3 and STAT5 phosphorylation. In addition, treatment with this Ab induced IEL apoptosis and wiped out the massive IEL accumulation in mice overexpressing human IL-15 in their gut epithelium. Together, our results delineate the IL-15-driven survival pathway in human IELs and demonstrate that IL-15 and its downstream effectors are meaningful therapeutic targets in RCDII.

CD8 and CD103 Are Highly Expressed in Asthmatic Bronchial Intraepithelial Lymphocytes

Background: Although characteristics of intraepithelial lymphocytes (IELs) in mucosal immunity have been well defined in the intestine, bronchial IELs have been little investigated. Recently, we showed that bronchial IELs have a distinct function that partly resembles that of intestinal IELs; however, surface antigen expression of bronchial IELs and the relationship of that expression to airway disease have not been studied. Methods: We analyzed phenotypic profiles of human bronchial IELs and lamina propria lymphocytes (LPLs) by double-staining immunohistochemistry using full-thickness bronchial specimens (10 nonasthmatic controls and 7 asthmatics) from lung resections. Results: In controls, the percentage of CD4+ cells was lower, and the percentage of CD8+ cells was higher in IELs compared to LPLs (CD4: median 50.0% in IELs vs. 65.9% in LPLs, p = 0.01; CD8: 50.9% in IELs vs. 34.4% in LPLs, p = 0.007). The percentage of cells positive for CD103 (αE-integrin) was higher in IELs than that in LPLs (median 60.1% in IELs vs. 16.9% in LPLs; p < 0.001). In IELs from asthmatics, these characteristics were particularly significant (CD4: median 26.2%, p = 0.008; CD8: 79.8%, p = 0.007; CD103: 76.2%, p = 0.019; all compared with IELs from nonasthmatics). Conclusions: These results suggest that human bronchial IELs have roles distinct from subsets of other lymphocytes, and that CD8+ cells and CD103+ cells have potentially important functions in the bronchial epithelium.

Interleukin 21 up‐regulates perforin‐mediated cytotoxic activity of human intra‐epithelial lymphocytes

Human intra-epithelial lymphocytes (IELs) are predominantly T-cell receptor-alphabeta(+) (TCR-alphabeta(+)) CD8(+) CD45RO(+) memory T cells located between intestinal epithelial cells. They respond to a greater extent to stimulation with interleukin (IL)-15 than to CD3/TCR triggering, suggesting that they react to the cytokine milieu in their local environment rather than to cognate antigen. A newly described member of the gammac cytokine family, IL-21, has potent antitumor effects. As IELs resemble lymphocytes infiltrating neoplastic lesions, their response to IL-21 may be relevant in vivo. Here, IL-21 was shown to increase perforin-mediated cytotoxicity and serine esterase release by IELs. This IL-21-mediated up-regulation occurred without changes in IEL survival or cell division. Interestingly, the effects of IL-21 occurred without increased phosphorylation of signal transducer and activator of transcription (STAT)1, STAT3, STAT4, STAT5, extracellular signal-regulated kinase (ERK), or p38. IL-21 had no effect on Fas ligand (FL)- or tumour necrosis factor-alpha (TNF-alpha)-mediated cytotoxicity, but it down-regulated IL-15-stimulated expression of CD25 and CD94, indicating that it has both positive and negative actions. This functional profile is unique to human IELs, emphasizing that they are a distinct compartment of lymphocytes and that IL-21 may promote their role in tumour immunosurveillance.

Human intestinal αβ IEL clones in celiac disease show reduced IL-10 synthesis and enhanced IL-2 production

Celiac disease is a gluten-induced T-cell mediated autoimmune process that results in the destruction of the intestinal mucosa and is associated with an expansion of CD8 + CD103 + TCRαβ intraepithelial lymphocytes (IELs) in the damaged epithelium. The role of this IEL population in the pathology is unknown. The aim of this work was to compare the cytokine profile and the cytotoxicity pattern from CD8 + IEL clones isolated from celiac (CD) and non-celiac (NCD) biopsies. We report that the number of IL-10 producing CD clones was significantly lower (26%) than that obtained from the NCD sample (62%). Instead, IL-2 was produced by more CD (44%) than NCD clones (26%). Cytotoxicity patterns against intestinal epithelial cell lines suggest different functional subsets of CD8 + IELs. CD clones capable of high cytotoxicity produced IL-2 whereas most cytotoxic NCD IELs produced IL-10. This clonal analysis indicates that an impaired immune regulation in celiac mucosa may be partially attributed to the low generation of regulatory CD8 + IELs that produce IL-10.

IL-4 down-regulates the responsiveness of human intraepithelial lymphocytes.

IL-4 is an important regulator of intestinal inflammation, yet little is known regarding its action on intestinal lymphocytes. Intestinal lymphocytes were isolated from jejunal mucosa of patients undergoing gastric bypass operations for morbid obesity. The impact of IL-4 was measured by its effects on proliferation using 3H-thymidine incorporation, IL-2 production using the CTLL assay, and IL-2 receptor generation using immunofluorescence. The production of IL-4 was measured by ELISA. IL-4 significantly inhibited the proliferation of intraepithelial lymphocytes (IEL) to a variety of stimuli as well as the development of lymphokine-activated killer (LAK) cells. In contrast, it had no effect on the proliferation of CD8+ T cells from peripheral blood. The inhibitory effect of IL-4 on IEL did not occur during activation, since IL-2 production and receptor expression were not altered. Rather, it occurred during cell cycling, since over 50% inhibition resulted whether IL-4 was added at the initiation of an IL-2-stimulated culture or after 24 or 48 h incubation. IL-4 was secreted by activated lamina propria lymphocytes (LPL) but not by IEL. IL-4, produced by activated LPL, may enter the epithelial compartment and down-regulate responsiveness of IEL.

Activation of human intraepithelial lymphocytes reduces CD3 expression.

The aim of this study was to examine in detail the low functional capacity of human intraepithelial lymphocytes (IELs) in response to phytohaemagglutinin (PHA) and CD3 ligation. Human IELs were extracted from jejunal mucosa obtained from patients undergoing gastric bypass operations for morbid obesity and compared to peripheral blood (PB) lymphocytes composed predominantly of CD8+ T cells. Calcium influx ([Ca2+]i) was analysed using Fura-2-loaded cells; IL-2 receptor expression was measured by immunofluorescence and flow cytometry; IL-2 binding was determined using radiolabelled IL-2; IL-2 production was quantified by ELISA; and apoptosis was detected with Apo 2.7 staining. Compared to naive PB CD8+ T lymphocytes, calcium influx by IELs was only transient with CD3 ligation and low in amplitude with PHA. IL-2 receptor expression was reduced after CD3 ligation, yet normal in numbers and affinity after PHA stimulation. Both cell types secreted similar amounts of IL-2. CD3 expression on IELs, but not PB CD8+ T cells, declined upon activation, due partly to incomplete reexpression after modulation. Little apoptosis was found. The partial activation of IELs in response to PHA and CD3 ligation, as manifested by diminished [Ca2+]i, resulted in a decline in CD3 expression.

Inhibitory effects of transforming growth factor-beta (TGF-beta) on certain functions of intraepithelial lymphocytes.

Human intraepithelial lymphocytes (IEL), CD8+ lymphocytes located between epithelial cells, are likely to be influenced by the immunosuppressive cytokine, TGF-beta, secreted by epithelial cells. This study evaluates the effects of TGF-beta on IEL functions. IEL were derived from proximal jejunum of patients undergoing gastric bypass operations for morbid obesity. Proliferation was determined by 3H-thymidine incorporation; IL-2 production, by ELISA; expression of IL-2 receptor, CD2, HML1, CD16, and CD56, by immunofluorescence; binding, by adherence of radiolabelled cells; and cytotoxicity by 51Cr-release assay. TGF-beta (> or = 1 ng/ml) inhibited the mitosis of IEL to mitogens, IL-7, and stimuli of the CD2 and CD3 pathways. The blocking effect did not target the activation events of IL-2 production and receptor generation. Rather, it reduced cell division after activation when added 24 h after initiating the culture. Antibody neutralization of naturally occurring TGF-beta increased IEL proliferation to IL-2, but not to the other stimuli. Of the multiple surface markers tested, only CD2 and HML1 expression increased with TGF-beta and decreased with antibody to TGF-beta, although the cytokine and the neutralizing antibody had no effects on IEL binding to colon cancer. TGF-beta reduced the number of CD56+ IEL and the lymphokine-activated killing when co-cultured with IL-7 but not with IL-2 or IL-15. TGF-beta inhibits certain IEL functions: the reduction in cell division rather than activation and a decline in IL-7-mediated lysis of colon cancer due to a lowering of the number of natural killer cells.

URETHRAL RECURRENCE AFTER RADICAL RADIOTHERAPY FOR BLADDER CANCER

Following cystectomy for bladder cancer, orthotopic reconstruction may result in a decreased risk of urethral recurrence compared to cutaneous diversion. We evaluate the rate of urethral recurrence after radical external beam radiotherapy. We reviewed the records of 214 men who had received radical radiotherapy at a single center from 1990 to 1995. Patients treated with chemotherapy were excluded from study. A total of 214 men (median age 69 years, range 39 to 86) underwent radical radiotherapy for cure. Tumor stages were T1 in 7%, T2 in 41%, T3 in 42% and T4a in 10% of the patients. Median followup was 32 months (range 1 month to 8.4 years) and 5-year survival rate was 30%. Urethral recurrence developed in 7 (3.2%) cases and was detected within 18 months (median 10 months, range 3 months to 5 years) of followup in 5. In 2 of these 7 cases recurrence developed in the prostatic urethra, and when these 2 cases were excluded from analysis the recurrence rate decreased to 2.3%. A total of 64 men completed 5-year followup, with a 4.7% rate of urethral recurrence (3.1% excluding prostatic urethral recurrence). Multifocal disease, bladder neck involvement, prostatic disease and cis were possible risk factors for urethral recurrence. The risk of urethral recurrence after radical radiotherapy for transitional cell carcinoma of the bladder is comparable with that reported after orthotopic reconstruction. It is not possible to exclude completely that men at higher risk were offered cystectomy, but the data are consistent with the suggestion that continued contact with urine may be protective.

Characterization of epithelial chemoattractants for human intestinal intraepithelial lymphocytes

Although homing of intraepithelial lymphocytes (IEL) into intestinal epithelia seems to be guided by signals from epithelia, little is known concerning functional epithelial-derived chemoattractants for IEL. Epithelial chemoattractants for IEL were analyzed using chemotaxis chamber system, enzyme-linked immunosorbent assay, and in situ hybridization using human epithelial lines and IEL lines. Epithelial-conditioned media induced IEL chemotaxis, and this activity was markedly enhanced by prestimulation of epithelia with interferon-(IFN)-gamma. This chemotaxis (stimulation +) was significantly inhibited by neutralizing antibodies to IFN-gamma inducible protein-10 (IP-10) or to monokine induced by IFN-gamma (MIG). Furthermore, while high amounts of IP-10 and MIG were detected in epithelial-conditioned media after IFN-gamma stimulation, equivalent concentrations of recombinant IP-10 and MIG reproduced IEL chemotaxis. Production of IP-10 and MIG in fresh epithelial cells was supported by in situ hybridization and enzyme-linked immunosorbent assay. Lastly, fresh human IEL constitutively expressed CXCR-3 (the common receptor for IP-10 and MIG), and fresh IEL also exhibited chemotaxis to by rIP-10, rMIG, and epithelial-conditioned media. Epithelial cells produce chemoattractants for IEL, and such chemokine production is regulated by proinflammatory cytokines such as IFN-gamma. IP-10 and MIG may serve as potentially important epithelial chemokines for IEL, especially under inflammatory conditions.

Migration of intestinal intraepithelial lymphocytes into a polarized epithelial monolayer.

Intraepithelial lymphocytes (IEL) are a phenotypically distinct population of lymphocytes that reside in mucosal epithelia, below the intercellular tight junctions. Although adhesive functions of this population have been previously studied, relatively little is known about IEL migration from the microvasculature into the epithelium. We demonstrated that cultured human IEL were capable of migration into polarized epithelial cells in vitro, where they assumed a subjunctional position, identical to that observed in vivo. The migration was rapid and efficient and was directionally polarized, such that IEL migrated into epithelial monolayers from the basolateral, but not the apical, aspect. After a 4-h period of residence, up to one-half of the IEL then exited the monolayer basolaterally. Migration was partially inhibited by pertussis toxin, suggesting a potential mechanism for IEL migration by chemokine receptor-mediated signaling. The conditions and ligand pairs used in IEL migration were different from those for neutrophils, another cell type known to migrate through epithelia. This system may serve as a model for microenvironmental homing of IEL into the epithelium.

Spontaneous secretion of interferon γ and interleukin 4 by human intraepithelial and lamina propria gut lymphocytes

Background—Cytokines secreted by intestinal T lymphocytes probably play a critical role in regulation of the gut associated immune responses.Aims—To quantify interferon γ (IFN-γ) and interleukin 4 (IL-4) secreting cells (SC)...

Intestinal intraepithelial lymphocytes have a promiscuous interleukin-8 receptor.

Human intraepithelial lymphocytes (IELs), predominantly T cells of the CD8+CD45RO+ phenotype that are situated between epithelial cells, have a chemotactic response to the alpha-chemokines, IL-8 and GRO, and the beta-chemokine, and the protein termed regulated on activation, normal T cell expressed and secreted (RANTES). To evaluate the specificity of the IL-8 receptor on IELs. Specificity was determined by the degree of desensitisation of the IL-8 response caused by each chemokine and the degree of inhibition of IL-8 binding to the cell. IELs migrated towards two additional beta chemokines, macrophage inflammatory protein-1 and monocyte chemotactic protein (MCP). All chemokines inhibited IL-8 induced chemotaxis and calcium ion mobilisation by IELs, with IL-8 having the greatest effect and MCP the least. In addition, specific binding of radiolabelled IL-8 to IELs was reduced by each of the five chemokines in cold competition experiments, whereas only GRO and IL-8 itself displaced 125I-IL-8 from receptors on peripheral blood mononuclear cells. The IL-8 responsiveness of IELs is desensitised by chemokines of both the alpha and beta families, and this is likely to occur by the binding of the chemokines to common receptors.

Human intestinal development in a severe-combined immunodeficient xenograft model

The present work describes a severe-combined immunodeficient murine xenograft model used to investigate human gastrointestinal ontogenesis. Specifically, the study has tested whether carefully selected regions of human fetal gut are able to undergo region-specific morphogenesis and epithelial cytodifferentiation when transplanted subcutaneously into immunodeficient mice. In addition, double-label in situ hybridisation techniques, utilising specific human and mouse DNA probes, have been adopted to characterise host and donor cell types and to investigate the potential developmental roles for non-epithelial cells in the regulation of epithelial differentiation pathways in vivo. Human fetal small and large bowel developed to form a characteristic mucosa 10 weeks after transplantation, which displayed clear region-specific structural and functional gradients. The initial phase of xenograft epithelialisation closely resembled the stratified type of epithelium which is present during early fetal gastrointestinal development. Idiosyncratic epithelial differentiation pathways were recorded during xenograft regeneration, with an absence of Paneth cells and an abundance of enteroendocrine cells when compared with developed xenograft and paediatric intestine. Such differences may, therefore, be important in ensuring rapid and region-specific development in the absence of conventional luminal stimuli and hormonal changes that occur normally during pregnancy. In situ hybridisation demonstrated an exclusively human origin for the intestinal xenograft epithelium and muscularis mucosa and externa. Although the submucosa and lamina propria were comprised of a chimeric mixture, murine cells were rarely seen to contact with the epithelium, which interacted primarily with human myofibroblasts and human intraepithelial lymphocytes. It is proposed that a ‘selection’ process operates to maintain species-specific cellular interactions, and this mechanism may subsequently play an important role in regulating epithelial cell differentiation, orchestrated in part by juxtaposed non-epithelial cell types.

GRO is chemotactic for human intestinal intraepithelial lymphocytes

: Human intraepithelial and lamina propria lymphocytes are memory lymphocytes that migrate from the circulation to the intestinal mucosa. We studied the effect of the chemokine, GRO, on these lymphocytes. Intraepithelial and lamina propria lymphocytes were isolated from human jejunal mucosa of healthy individuals and cultured for three days in IL-2. Migration was assessed using the Boyden transwell assay. Increases in cytoplasmic free calcium concentration were measured by changes in fluorescence of Fura-2-loaded lymphocytes upon exposure to GRO. A large number of intraepithelial lymphocytes (IEL) but few lamina propria lymphocytes (LPL) migrated toward GROα, GROβ, and GROy. Checkerboard experiments showed that the response of intraepithelial lymphocytes was mainly by chemotaxis rather than chemokinesis. The action of GROa was independent of cytochalasin D, staurosporine, and pertussis toxin but was inhibited by sodium azide and cycloheximide. None of the GRO proteins triggered calcium mobilization by either lymphocyte type. This study shows that GRO is chemotactic for IEL but not LPL.

Adhesion molecules utilized in binding of intraepithelial lymphocytes to human enterocytes

The expression of adhesion molecules by human duodenal intraepithelial lymphocytes (IEL) was examined by two-color flow cytometry. Resting IEL expressed LFA-1, HML-1, CD44. Stimulation with phytohemagglutinin (PHA) resulted in down-regulation of expression of these molecules with induction of expression of ICAM-1 and VLA-4. VLA-4 expression was also found on non-activated IEL from patients with celiac disease. In addition, IEL expressed an antigen recognized by a novel monoclonal antibody D2.1. The molecular mass of D2.1 is heterogeneous: 82 kDa in peripheral blood lymphocytes and 44 kDa in an IEL line. Expression of this antigen was also up-regulated by PHA. To determine the involvement of these antigens in binding of IEL to human enterocytes, we developed a system based on adherence of an IEL cell line to the I407 fetal intestinal cell line. Monoclonal antibodies VLA-4, D2.1 and to a lesser extent ICAM-1 blocked adherence of IEL to I407 cells. These data suggest that VLA-4 and D2.1 may be involved in adherence of IEL to human enterocytes or secreted matrix molecules in vivo.

Human intestinal intraepithelial lymphocytes are derived from a limited number of T cell clones that utilize multiple V beta T cell receptor genes.

Intestinal intraepithelial lymphocytes (IEL) are a phenotypically distinct T cell population of unknown function. The majority of human intestinal IEL express the TCR-alpha beta, the CD8 accessory molecule, and the CD45RO Ag, suggesting that they are MHC class I-restricted memory T cells. Recent analyses of the TCR alpha- and beta-chains expressed by these cells have shown marked skewing toward one or several V region genes in individual donors and revealed the presence of clonally expanded cells. In addition, functional data has suggested that the MHC class I-like CD1 molecules may be the target ligands for some human intestinal IEL clones. This report examines in detail the TCR-beta repertoire of human jejunal IEL to determine what fraction of these cells are clonally expanded and to determine whether a particular subset of V beta genes are utilized by the clonally expanded cells. The results demonstrate that the majority of IEL are derived from the expansion of a relatively few T cell clones and that these clones can utilize a large number of different V beta genes. Oligoclonal expansion is also demonstrated among lamina propria lymphocytes (LPL), with overlapping but distinct clones detected in the LPL vs the IEL populations. These results indicate that most intestinal IEL-alpha beta, and a subpopulation of LPL, are specific for a limited number of Ag and place constraints on the possible roles played by IEL in the defense against diverse environmental pathogens or in the generation of oral tolerance.