Review article: the gastrointestinal complications of myositis

BACKGROUND

The inflammatory myopathies are a group of acquired diseases characterized by a proximal myopathy caused by an inflammatory infiltrate of the skeletal muscle. The three major diseases are dermatomyositis, polymyositis and inclusion body myositis.

AIMS

To review the gastrointestinal manifestations of myositis.

METHODS

Over 110 articles in the English literature were reviewed.

RESULTS

Dysphagia to solids and liquids occurs in patients with myositis. The pharyngo-oesophageal muscle tone is lost and therefore patients develop nasal speech, hoarseness, nasal regurgitation and aspiration pneumonia. There is tongue weakness, flaccid vocal cords, poor palatal motion and pooling of secretions in the distended hypopharynx. Proximal oesophageal skeletal muscle dysfunction is demonstrated by manometry with low amplitude/absent pharyngeal contractions and decreased upper oesophageal sphincter pressures. Patients exhibit markedly elevated creatine kinase and lactate dehydrogenase levels consistent with muscle injury. Myositis can be associated with inflammatory bowel disease, coeliac disease and interferon treatment of hepatitis C. Corticosteroids and other immunosuppressive drugs comprise the mainstay of treatment. Inclusion body myositis responds poorly to these agents and therefore a myotomy is usually indicated.

CONCLUSION

Myositis mainly involves the skeletal muscles in the upper oesophagus with dysphagia, along with proximal muscle weakness.

Patients with inflammatory bowel disease may have a transforming growth factor-beta-, interleukin (IL)-2- or IL-10-deficient state induced by intrinsic neutralizing antibodies

Ulcerative colitis (UC) and Crohn's disease (CD) are considered to be immunologically mediated disorders that share certain features with murine models of colitis. Whether any of these models are physiologically relevant to the human condition remains controversial. The hypothesis is that increased amounts of antibodies neutralizing transforming growth factor (TGF)-beta, interleukin (IL)-2 or IL-10 create a relative immunodeficient state in inflammatory bowel disease (IBD) that predisposes to disease. To evaluate this, serum samples from patients with UC or CD and from normal healthy individuals were studied by enzyme-linked immunosorbent assays. Antibodies recognizing TGF-beta were most prevalent in UC (P<0.01); anti-IL-10 antibodies were elevated in CD (P<0.05), while anti-IL-2 antibodies were the same for all three groups. Importantly, the percentage of IBD patients with at least one of the antibody levels greater than any control value was 30% for UC and 33% for CD. To verify the presence of these antibodies, immobilized TGF-beta was exposed to UC sera and the attached proteins identified by Western blot assay. The proteins proved to be exclusively immunoglobulin (Ig) G. To evaluate the neutralizing activity of these antibodies, cytokine-specific IgG from subjects in each group of patients was incubated with TGF-beta, IL-2 or IL-10 before addition to a bioassay with changes in viability determined by a colorimetric analysis. Antibodies from most individuals in all three groups neutralized the action of each cytokine. This study shows that about one-third of IBD patients may have a relative deficiency of TGF-beta, IL-2 or IL-10 due to an increase in neutralizing antibodies in their sera.

Non-response to infliximab may be due to innate neutralizing anti-tumour necrosis factor-alpha antibodies

Infliximab is a chimeric anti-tumour necrosis factor (TNF)-alpha antibody that is therapeutic in many patients with inflammatory bowel disease. What causes certain patients not to respond is unknown. The question posed is whether innate anti-TNF-alpha antibodies play any role in the response to infliximab. Blood was drawn prior to the initial dose of infliximab. Serum anti-TNF-alpha antibodies were quantitated by enzyme-linked immunosorbent assay (ELISA). Affinity-purified anti-TNF-alpha antibodies were isolated from serum immunoglobulin G using TNF-alpha-coated beads. The ability of these antibodies to induce apoptosis of macrophages was measured by annexin and propidium iodide staining. Changes in TNF receptor type 2 (TNFR2) expression and release were determined by immunofluorescence and ELISA respectively. TNF-alpha-neutralization was assessed by the reversal of the lytic actions of TNF-alpha on WEHI cells. The amounts of innate anti-TNF-alpha antibodies in the serum from infliximab responders versus non-responders were the same. Apoptosis of monocytes increased with infliximab and by several of the purified anti-TNF-alpha antibodies, but these findings did not vary with the patients' responses to infliximab. Effects of the anti-TNF-alpha antibodies on the expression of TNFR2 on monocytes and their release of soluble TNFR2 did not vary with the patients' responses to infliximab. However, the neutralizing capacity of these antibodies differed, with responders having antibodies that reduced only 47 +/- 4% of the TNF-alpha activity while those from non-responders reduced 70 +/- 5% of the TNF-alpha activity (P < 0.01). Non-responders have innate anti-TNF-alpha antibodies with greater neutralizing activity than antibodies from responders. Any TNF-alpha-mediated disease process would be neutralized by intrinsic antibodies, so that the disease is likely to be driven by non-TNF-alpha-mediated events.

Activation antigens on colonic T cells in inflammatory bowel disease: effects of IL-10

Activated T cells that express activation antigens are termed nonprofessional antigen-presenting cells (T-APCs). This study evaluates the ability of lamina propria lymphocytes (LPLs) in inflammatory bowel disease (IBD) to become T-APCs. LPLs were stained by two-colour immunofluorescence to determine the expression of activation antigens on T cells. Those from actively inflamed IBD mucosa expressed greater amounts of MHC class II (DR) and CD86 than did LPL T cells from disease controls or normal individuals. After culture in IL-2 with or without IL-10, the ability of the T-APCs from IBD colon to stimulate allogeneic peripheral blood T cell proliferation was measured. The T-APCs from IBD stimulated an allogeneic mixed lymphocyte reaction, particularly through their expression of DR and CD86, as demonstrated by antibody blocking. Normal LPLs acquired these properties only if repeatedly stimulated with allogeneic peripheral blood lymphocytes (PBLs) used as cell lines in the presence of IL-2. Addition of IL-10 reduced expression of activation antigens and the stimulatory ability of LPLs from either IBD patients or from these cell lines. In summary, LPLs from active IBD, but not from disease controls, express activation antigens that stimulate naïve T cells, a process that is reduced by IL-10. This may contribute to perpetuation of the inflammation.

Interleukin-12 up-regulates perforin- and Fas-mediated lymphokine-activated killer activity by intestinal intraepithelial lymphocytes

Human intraepithelial lymphocytes (IELs) comprise a unique compartment of memory T cell receptor (TCR)-alphabeta( +)CD8(+) T lymphocytes interspersed between intestinal epithelial cells. They develop potent lymphokine-activated killer (LAK) activity with interleukin (IL)-15, a cytokine that is found in excess in certain mucosal inflammatory states. IL-12, released by activated antigen-presenting cells, is known to potentiate perforin-induced cytotoxicity. This study evaluates the mechanism by which IL-12 up-regulates LAK activity. When IELs were stimulated with IL-15, the CD94(+) IEL subset expanded and carried out cytotoxic activity in redirected lysis against P815 cells as well as Fas ligand (FL)- and tumour necrosis factor (TNF)-alpha-mediated lysis of Jurkat and WEHI cells, respectively. IL-12 enhanced the perforin- and FL-, but not TNF-alpha-mediated events. In addition, the up-regulated killing of HT-29 cells by IL-12 was reduced by concanamycin (which targets perforin) and antibody neutralizing FL but not by anti-TNF-alpha antibody. Furthermore, IL-12 augmented IL-15-stimulated release of serine esterases as well as expression of perforin and FL by IELs, but not TNF-alpha. This study shows that LAK activity, carried out by the CD94(+) IELs, involves perforin, FL and TNF-alpha. IL-12 up-regulates the first two mechanisms of action, showing for the first time its effect on FL production and lytic activity.

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.

NKG2D receptors induced by IL-15 costimulate CD28-negative effector CTL in the tissue microenvironment

Unlike primary T cells in lymph nodes, effector CD8(+) CTL in tissues do not express the costimulatory receptor CD28. We report that NKG2D, the receptor for stress-induced MICA and MICB molecules expressed in the intestine, serves as a potent costimulatory receptor for CTL freshly isolated from the human intestinal epithelium. Expression and function of NKG2D are selectively up-regulated by the cytokine IL-15, which is released by the inflamed intestinal epithelium. These findings identify a novel CTL costimulatory pathway regulated by IL-15 and suggest that tissues can fine-tune the activation of effector T cells based on the presence or absence of stress and inflammation. Uncontrolled secretion of IL-15 could lead to excessive induction of NKG2D and thus contribute to the development of autoimmune disease by facilitating the activation of autoreactive T cells.

Lamina propria lymphocytes produce interferon-gamma and develop suppressor activity in response to lactoglobulin

This study examines the in vitro response of human lamina propria lymphocytes (LPLs) to food antigens. LPLs were obtained from jejunum of healthy individuals undergoing gastric bypass operations for morbid obesity. Proliferation was assayed by [3H]thymidine incorporation and cytokine production by ELISA. LPLs proliferated in response to keyhole limpet hemocyanin, ovalbumin, lactoglobulin, and phytohemagglutinin (PHA), but not to yeast. The responses to lactoglobulin and PHA were inhibited by the CTLA4/Fc chimera and by MAbs against CD2, CD58, CD80, and CD86, indicating stimulation of CD28+ LPLs with antigen-presenting cells through activation of the CD2 pathway. Besides producing IL-2, IL-10, and TNF-alpha, LPLs synthesized large amounts of IFN-gamma (100 ng/ml) with lactoglobulin, a process dependent upon CD80/CD86, CD40/CD40L, and IL-12. After a three-day culture with lactoglobulin, ovalbumin, or PHA, LPLs developed suppressor activity that reduced proliferation of naive LPLs to these same stimuli. In summary, LPLs first respond to lactoglobulin by proliferation and IFN-gamma production, then by development of antigen nonspecific suppression.

Staphylococcal enterotoxin B induces potent cytotoxic activity by intraepithelial lymphocytes

In food poisoning, Staphylococcus aureus secretes staphylococcal enterotoxin B (SEB), a superantigen that causes intense T-cell proliferation and cytotoxicity. The effects of SEB on lytic activity by human intestinal intraepithelial lymphocytes (IEL) were investigated. Jejunal IEL, from morbidly obese individuals undergoing gastric bypass operations, were tested for SEB-induced cytotoxicity against C1R B-lymphoblastoid cells, HT-29 adenocarcinoma cells, or CD1d-transfected cells using the 51Cr-release assay. Fas and Fas ligand expression were detected by immunofluorescence and flow cytometry and soluble ligand by enzyme-linked immunosorbent assay (ELISA). In the presence of SEB, IEL became potently cytotoxic against C1R cells and interferon-gamma (IFN-gamma)-precultured HT-29 cells, causing 55+/-10% and 31+/-6% lysis, respectively, greater than that by phytohaemagglutinin (PHA)-, interleukin-2 (IL-2)-, or anti-T-cell receptor (TCR)-activated IEL. SEB-stimulated peripheral blood (PB) CD8+ T cells lysed similar numbers of C1R cells but fewer HT-29 cells (53+/-13% and 8+/-5%, respectively). IEL killing of C1R cells involved interaction of major histocompatibility complex (MHC) class II with TCR, CD2 with CD58, and CD11a with CD54, and was perforin mediated. SEB-induced IEL lysis of HT-29 cells, in contrast, was caused by an unknown target cell structure, not MHC class II or CD1d, and resulted from a combination of perforin and Fas-mediated events. The potent cytotoxic activities of IEL promoted by SEB utilize two different mechanisms, depending on the surface receptors expressed by the target cells.

Selective expansion of intraepithelial lymphocytes expressing the HLA-E-specific natural killer receptor CD94 in celiac disease

BACKGROUND & AIMS

Celiac disease is a gluten-induced enteropathy characterized by the presence of gliadin-specific CD4(+) T cells in the lamina propria and by a prominent intraepithelial T-cell infiltration of unknown mechanism. The aim of this study was to characterize the subset(s) of intraepithelial lymphocytes (IELs) expanding during active celiac disease to provide insights into the mechanisms involved in their expansion.

METHODS

Flow-cytometric analysis of isolated IELs and/or immunohistochemical staining of frozen sections were performed in 51 celiac patients and 50 controls with a panel of monoclonal antibodies against T-cell and natural killer (NK) receptors. In addition, in vitro studies were performed to identify candidate stimuli for NK receptor expression.

RESULTS

In normal intestine, different proportions of IELs, which were mainly T cells, expressed the NK receptors CD94/NKG2, NKR-P1A, KIR2D/3D, NKp46, Pen5, or CD56. During the active phase of celiac disease, the frequency of CD94(+) IELs, which were mostly alphabeta T cells, was conspicuously increased over controls. In contrast, the expression of other NK markers was not modified. Furthermore, expression of CD94 could be selectively induced in vitro by T-cell receptor activation and/or interleukin 15, a cytokine produced by intestinal epithelial cells.

CONCLUSIONS

The gut epithelium favors the development of T cells that express NK receptors. In active celiac disease, there is a specific and selective increase of IELs expressing CD94, the HLA-E-specific NK receptor that may be related to T-cell receptor activation and/or interleukin 15 secretion.

Constitutive expression of stromal derived factor-1 by mucosal epithelia and its role in HIV transmission and propagation

HIV particles that use the chemokine receptor CXCR4 as a coreceptor for entry into cells (X4-HIV) inefficiently transmit infection across mucosal surfaces [1], despite their presence in seminal fluid and mucosal secretions from infected individuals [2] [3] [4]. In addition, although intestinal lymphocytes are susceptible to infection with either X4-HIV particles or particles that use the chemokine receptor CCR5 for viral entry (R5-HIV) during ex vivo culture [5], only systemic inoculation of R5-chimeric simian-HIV (S-HIV) results in a rapid loss of CD4(+) intestinal lymphocytes in macaques [6]. The mechanisms underlying the inefficient capacity of X4-HIV to transmit infection across mucosal surfaces and to infect intestinal lymphocytes in vivo have remained elusive. The CCR5 ligands RANTES, MIP-1alpha and MIP-1beta suppress infection by R5-HIV-1 particles via induction of CCR5 internalization, and individuals whose peripheral blood lymphocytes produce high levels of these chemokines are relatively resistant to infection [7] [8] [9]. Here, we show that the CXCR4 ligand stromal derived factor-1 (SDF-1) is constitutively expressed by mucosal epithelial cells at sites of HIV transmission and propagation. Furthermore, CXCR4 is selectively downmodulated on intestinal lymphocytes within the setting of prominent SDF-1 expression. We postulate that mucosally derived SDF-1 continuously downmodulates CXCR4 on resident HIV target cells, thereby reducing the transmission and propagation of X4-HIV at mucosal sites. Moreover, such a mechanism could contribute to the delayed emergence of X4 isolates, which predominantly occurs during the later stages of the HIV infection.

Human intestinal lamina propria and intraepithelial lymphocytes express receptors specific for chemokines induced by inflammation

To determine which chemokine receptors might be involved in T lymphocyte localization to the intestinal mucosa, we examined receptor expression on human intestinal lamina propria lymphocytes (LPL), intraepithelial lymphocytes (IEL) and CD45RO+beta7hi gut homing peripheral blood lymphocytes (PBL). Virtually all LPL and IEL expressed CXCR3 and CCR5, receptors that have been associated with Th1(Tc1)/Th0 lymphocytes, while CCR3 and CCR4, receptors associated with Th2 (Tc2)lymphocytes, CCR7, CXCR1 and CXCR2 were not expressed. CXCR3 and CCR5 receptors were functional, as LPL and IEL migrated to their respective ligands I-TAC and RANTES. In addition, most alphaEbeta7- LPL and IEL expressed high levels of CCR2. While the majority of CD45RO(-)beta7hi PBL also expressed CXCR3 and CCR5, a proportion of these cells were CXCR3- and/or CCR5- and some expressed CCR4 and/or CCR7, indicating that lymphocytes recruited to the intestinal mucosa represent a subset of these cells. In summary, our results show that LPL and IEL within the normal intestine express a specific and similar array of chemokine receptors whose ligands are constitutively expressed in the intestinal mucosa and whose expression is up-regulated during intestinal inflammation. These results support the view that CXCR3, CCR5 and CCR2 may play an important role in lymphocyte localization within the intestinal mucosa.

IL-10 enhances IL-2-induced proliferation and cytotoxicity by human intestinal lymphocytes

IL-10 modulation of human intestinal T lymphocyte functions was studied for the first time. Lymphocyte proliferation was determined by 3H-thymidine incorporation; cytokine production, by ELISA; expression of surface markers, by immunofluorescence and flow cytometric analysis; and cytotoxicity, by lysis of 51Cr-labelled target cells. IL-10 blocked phytohaemagglutinin (PHA)-induced activation and proliferation of CD8+ T cells from the epithelium and lamina propria. It was a greater inhibitor of IL-2, interferon-gamma, and tumour necrosis factor-alpha production than were IL-4 or transforming growth factor-beta. In contrast, IL-10 enhanced IL-2-stimulated proliferation of both CD4+ and CD8+ T cells by increasing cell division after activation. It also augmented IL-2- but not IL-15-induced cytotoxicity of intestinal lymphocytes against colon cancer by a mechanism independent of natural killer cells. In conclusion, IL-10 blocking of proinflammatory cytokine secretion probably reduces intestinal inflammation. IL-10 augmentation of IL-2-induced cytotoxicity may help to maintain host defence.

Human intestinal lamina propria and intraepithelial lymphocytes express receptors specific for chemokines induced by inflammation

To determine which chemokine receptors might be involved in T lymphocyte localization to the intestinal mucosa, we examined receptor expression on human intestinal lamina propria lymphocytes (LPL), intraepithelial lymphocytes (IEL) and CD45RO+beta7hi gut homing peripheral blood lymphocytes (PBL). Virtually all LPL and IEL expressed CXCR3 and CCR5, receptors that have been associated with Th1(Tc1)/Th0 lymphocytes, while CCR3 and CCR4, receptors associated with Th2 (Tc2)lymphocytes, CCR7, CXCR1 and CXCR2 were not expressed. CXCR3 and CCR5 receptors were functional, as LPL and IEL migrated to their respective ligands I-TAC and RANTES. In addition, most alphaEbeta7- LPL and IEL expressed high levels of CCR2. While the majority of CD45RO(-)beta7hi PBL also expressed CXCR3 and CCR5, a proportion of these cells were CXCR3- and/or CCR5- and some expressed CCR4 and/or CCR7, indicating that lymphocytes recruited to the intestinal mucosa represent a subset of these cells. In summary, our results show that LPL and IEL within the normal intestine express a specific and similar array of chemokine receptors whose ligands are constitutively expressed in the intestinal mucosa and whose expression is up-regulated during intestinal inflammation. These results support the view that CXCR3, CCR5 and CCR2 may play an important role in lymphocyte localization within the intestinal mucosa.

Integrin alpha1beta1 (VLA-1) mediates adhesion of activated intraepithelial lymphocytes to collagen

Intraepithelial lymphocytes (IELs) from human intestinal epithelium are memory CD8+ T cells that bind to epithelial cells through human mycosal lymphocyte (HML)-1 and to mesenchymal cells through very late activation antigen-4 (VLA-4). Their binding of extracellular matrix proteins and the mechanism involved were tested. Activated 51Cr-labelled lymphocytes were incubated in protein-coated microwells with various additives. After washing, the adherent cells were detected by radioactivity. The percentages of activated IELs that bound to collagen types I and IV were 20 and 31%, respectively; fewer bound to fibronectin or laminin. Compared to interleukin-2-activated peripheral blood CD8+ T lymphocytes, more IELs bound collagen IV and fewer bound fibronectin. IEL adhesion to collagen (but not fibronectin or laminin) was up-regulated by antibody ligation of CD2 or by protein kinase C stimulation by phorbol ester; staurosporine reduced binding, while herbimycin, phytohaemagglutinin and CD3 ligation had no effect. Antibody-blocking of integrin VLA-1 subunits alpha1 (CD49a) and beta1 (CD18) inhibited adhesion to collagen type I by 82+/-6% and to type IV by 94+/-1% (P<0.001), implicating VLA-1 as the main collagen receptor for IELs. Cell adhesion was dependent on extracellular divalent cations, a characteristic event of VLA-1 never before shown for IELs: manganese and magnesium ions supported binding in a dose-dependent manner; calcium ions inhibited their effectiveness. Therefore, IELs bind collagen through integrin alpha1beta1 after protein kinase C activation. Adhesion is modulated by divalent cations.

Giardia induces proliferation and interferon gamma production by intestinal lymphocytes

BACKGROUND

Murine intraepithelial lymphocytes kill Giardia lambia; responses of human intestinal lymphocytes to this parasite are unknown.

AIMS

To examine giardia induced proliferation, interferon gamma production, migration, and cytotoxicity by lymphocytes from the human intestine and peripheral blood.

METHODS

Giardia were added to intraepithelial lymphocytes, lamina propria lymphocytes, and peripheral blood lymphocytes, obtained from jejunal mucosa and blood of otherwise healthy patients undergoing gastric bypass surgery for morbid obesity. Proliferation was measured by 3H-thymidine incorporation; frequency of proliferation precursors, by limiting dilution analysis; interferon gamma production, by ELISA; cytotoxicity, by 51Cr release of radiolabelled giardia and by release of serine esterases by effector lymphocytes that mediate cytotoxicity.

RESULTS

The CD4+ T lymphocytes from intestine and blood proliferated in response to giardia. The stimulus by the parasite was mitogenic rather than antigenic due to the fact that the peak response was on day 3 rather than day 6, and the large number of precursors was in the range of that for mitogens. CD4+ T lymphocytes from both sites produced interferon gamma in response to giardia. Lymphocytes did not migrate towards or kill the parasite.

CONCLUSIONS

Giardia induced the same degree of proliferation and interferon gamma production by CD4+ T lymphocytes in intestine and blood, but did not trigger cytotoxicity or migration.

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.

Interleukin 15 is a potent stimulant of intraepithelial lymphocytes

BACKGROUND & AIMS

This study examined the effects of interleukin (IL)-15 on intraepithelial lymphocytes (IELs) because they resemble memory cells that react to IL-15 and are located next to epithelial cells that produce IL-15.

METHODS

Proliferative responses were measured by [3H]thymidine uptake; interferon (IFN)-gamma production by enzyme-linked immunosorbent assay; and cytotoxicity production by lysis of 51Cr-labeled HT-29 cells.

RESULTS

The proliferative response of IELs was much greater with IL-15 than with equivalent amounts of IL-2 or IL-7 (P < 0.001); the same level of blastogenesis was induced by 10(3)-fold less IL-15 than IL-2. Production of IFN-gamma was also highest when IELs were stimulated with IL-15. IELs lysed more 51Cr-labeled HT-29 cells when cultured for 72 hours with IL-15 (48% +/- 3% at 25:1 effector-to-target ratio) than with IL-2 (27% +/- 3%) or IL-7 (12% +/- 2%) (P < 0.0001). Similarly, limiting dilution analysis revealed a greater frequency of cytotoxic precursors in IELs that were stimulated by IL-15 rather than IL-2: 1/467 vs. 1/1900. But IL-15 did not alter the number of natural killer cells, as determined by quantitating CD16 and CD56 by immunofluorescence. Rather, it increased serine esterase content in IELs.

CONCLUSIONS

IL-15 is the most potent of the known cytokines for IELs, inducing the highest levels of proliferation, IFN-gamma production, and cytotoxicity.

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.

Tumour necrosis factor-alpha enhances intraepithelial lymphocyte proliferation and migration

BACKGROUND

Tumour necrosis factor alpha (TNF-alpha) is a proinflammatory cytokine found in abundance in diseased intestine.

AIMS

The T cell production of TNF-alpha and the impact of this cytokine on intestinal T cell proliferation, migration, and cytotoxicity were studied.

METHODS

Intestinal lymphocytes from normal jejunum were used. TNF-alpha production in culture supernates was measured by enzyme linked immunosorbent assay (ELISA). Lymphocyte proliferation was measured using 3H thymidine uptake; migration, using transwell chambers; and cytotoxicity of HT-29 colon cancer cells, using the chromium-51 release assay.

RESULTS

TNF-alpha was produced mainly by the CD8+ T cells in the intraepithelial lymphocytes (IEL) and the CD4+ T cells in the lamina propria lymphocytes in response to CD2 stimulation: 478 (94) and 782 (136) pg/ml, respectively. TNF-alpha (1 ng/ml or greater) augmented proliferation of IEL in response to interleukin 2 (IL-2), IL-7, or antibody to CD3 due to increased activation that did not involve IL-2 production or receptor generation. Conversely, antibody to TNF-alpha reduced IEL proliferation in response to IL-2 or IL-7. TNF-alpha also induced calcium mobilisation and chemokinesis (by 2.8 (0.5) fold over spontaneous migration). TNF-alpha had no effect on lymphokine activated killer cell activity.

CONCLUSIONS

TNF-alpha increases the proliferation and migration of IEL, which may expand their number in the epithelium.

Intraepithelial lymphocytes in normal human intestine do not express proteins associated with cytolytic function

Human small intestine contains a very large population of intraepithelial T lymphocytes (IELs) that are oligoclonal, appear functionally to be cytolytic T cells, and may contribute to the normal and pathological turnover of intestinal epithelial cells. This report addresses the cytolytic function of IELs in normal small intestine by examining their expression of molecules that carry out cell-mediated cytolysis. Immunohistochemical analyses of granzyme B, perforin, Fas ligand, and tumor necrosis factor-alpha demonstrated these proteins were not expressed by small intestinal IELs in situ. These proteins also were not expressed by colonic IELs or by lamina propria lymphocytes in the small or large intestine. Granzyme A, however, was expressed by a large fraction of IELs. In contrast to these in situ results, isolated and in vitro activated IELs were shown to express effector proteins consistent with cytolytic T cells, including granzyme B, Fas ligand, tumor necrosis factor-alpha, and interferon-gamma. These results are most consistent with the vast majority of IELs in normal human small intestine being resting cytolytic T cells and suggest that these cells do not contribute to the apoptotic cell death of epithelial cells in normal intestine.

Mesenchymal cells stimulate human intestinal intraepithelial lymphocytes

BACKGROUND & AIMS

Intraepithelial lymphocytes (IELs) from human intestinal mucosa proliferate minimally to T-cell stimuli. Optimal growth may depend on factors that are missing in vitro, such as accessory cells. The aim of this study was to determine whether mesenchymal cells costimulate IELs.

METHODS

IELs were isolated from human jejunum and cultured with fibroblasts or smooth muscle cells (mesenchymal cell models for mucosal myofibroblasts) and various T-cell stimuli. Proliferation was determined by [3H]thymidine incorporation, and interleukin 2 (IL-2) production was measured by enzyme-linked immunosorbent assay. Surface molecules were detected by immunofluorescence and flow cytometry.

RESULTS

The proliferative responses of IELs to mitogen (phytohemagglutinin), superantigen (staphylococcal enterotoxin B), or anti-CD3 antibody were increased greatly by coculture with mesenchymal cells, while only slightly by peripheral-blood monocytes, the classical antigen-presenting cells. IL-2 production and receptor expression also increased. Mesenchymal cell costimulation of IEL growth required direct contact between the two cell types and was partly dependent on the integrin alpha4beta1 (very late activation 4[VLA-4]) and major histocompatibility complex (MHC) class I, as their respective antibodies blocked the effect. The surface molecules B7 (CD80), CD2, and MHC class II were not involved.

CONCLUSIONS

Optimal IEL growth depends on their contact with mesenchymal cells, an interaction that is mediated by VLA-4 and MHC class I. In mucosal immunity, basement membrane myofibroblasts likely serve this role.

Intestinal perforation. A common complication of scleroderma

The known intestinal complications of systemic sclerosis (SSc) stem mainly from motor disturbances. Autopsy findings were studied to identify anatomic abnormalities that may be associated with this disease. Descriptions of intestinal organs at autopsy were compared in 16 patients with SSc and 18 patients with systemic lupus erythematosus (SLE), a related disease control. There was a high incidence of perforation in SSc (7 of 16 patients) compared to SLE (1 of 18 patients) (P < 0.05). In SSc, perforations involved all parts of the bowel: transmural esophageal fibrosis (after heater probe cautery), dehiscence of suture line after gastric resection, perforated duodenal ulcers (N = 2), terminal ileal ischemia, and diverticulitis (N = 2). Two of the perforations in SSc were silent and were discovered at autopsy. The one perforation in SLE was due to full-thickness necrosis from vasculitis. This study suggests that the intestinal walls of patients with SSc are inherently weak; the gastroenterologist should keep this in mind when performing invasive procedures.

Intestinal intraepithelial lymphocytes have a promiscuous interleukin-8 receptor

BACKGROUND

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).

AIM

To evaluate the specificity of the IL-8 receptor on IELs.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

p126 (CDw101), a costimulatory molecule preferentially expressed on mucosal T lymphocytes

Intestinal mucosal lymphocytes are defined by their anatomic location within the epithelium (intraepithelial lymphocytes), the interstitium between the epithelial basement membrane and the underlying muscularis mucosa (lamina propria lymphocytes), or in organized lymphoid tissues (Peyer's patches). Although intestinal intraepithelial lymphocytes have a distinct localization, their function has not been determined. To define cell surface proteins that are involved in intestinal intraepithelial lymphocyte localization or function, cultured human mucosal lymphocytes were used as immunogens to develop mAbs that react predominantly with this cell population in an immunohistochemical screening assay. Three mAbs were selected that subsequently were found by biochemical analysis to identify a 200-kDa homodimeric polypeptide on 88 to 98% of CD3+ mucosal lymphocytes but only 18 +/- 13% of PBLs. Expression on granulocytes and monocytes was also observed. This polypeptide has been termed p126 based on its SDS-PAGE-determined M(r) under reducing conditions. Cleveland digest maps demonstrated similarity between the p126 and CDw101 polypeptides. Determined amino acid sequence analysis of the purified p126 polypeptide revealed that it is the protein product of the recently identified V7 gene, which has structural similarities to members of the Ig gene superfamily. Two of the anti-p126 mAbs were costimulatory with suboptimal concentrations of anti-CD3 mAb inducing proliferation of cultured intestinal intraepithelial lymphocytes. Thus, we conclude that p126 is CDw101 encoded by a gene that predicts a seven-Ig domain chain-like structure. It has restricted expression predominantly on mucosal T lymphocytes and appears to have a costimulatory function of special relevance for CD28- T cells and for mucosal lymphocytes.

p126 (CDw101), a costimulatory molecule preferentially expressed on mucosal T lymphocytes

Intestinal mucosal lymphocytes are defined by their anatomic location within the epithelium (intraepithelial lymphocytes), the interstitium between the epithelial basement membrane and the underlying muscularis mucosa (lamina propria lymphocytes), or in organized lymphoid tissues (Peyer's patches). Although intestinal intraepithelial lymphocytes have a distinct localization, their function has not been determined. To define cell surface proteins that are involved in intestinal intraepithelial lymphocyte localization or function, cultured human mucosal lymphocytes were used as immunogens to develop mAbs that react predominantly with this cell population in an immunohistochemical screening assay. Three mAbs were selected that subsequently were found by biochemical analysis to identify a 200-kDa homodimeric polypeptide on 88 to 98% of CD3+ mucosal lymphocytes but only 18 +/- 13% of PBLs. Expression on granulocytes and monocytes was also observed. This polypeptide has been termed p126 based on its SDS-PAGE-determined M(r) under reducing conditions. Cleveland digest maps demonstrated similarity between the p126 and CDw101 polypeptides. Determined amino acid sequence analysis of the purified p126 polypeptide revealed that it is the protein product of the recently identified V7 gene, which has structural similarities to members of the Ig gene superfamily. Two of the anti-p126 mAbs were costimulatory with suboptimal concentrations of anti-CD3 mAb inducing proliferation of cultured intestinal intraepithelial lymphocytes. Thus, we conclude that p126 is CDw101 encoded by a gene that predicts a seven-Ig domain chain-like structure. It has restricted expression predominantly on mucosal T lymphocytes and appears to have a costimulatory function of special relevance for CD28- T cells and for mucosal lymphocytes.

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.

Mechanisms of colon cancer binding to substratum and cells

Binding of colon cancer to extracellular matrix (ECM) proteins and mesenchymal cells that comprise the basement membrane is important in migration and metastasis. This study defines the conditions and surface structures necessary for adhesion of HT-29 cells to ECM proteins and cell monolayers. Binding began within minutes and peaked by 1 hr, with 80-95% of HT-29 cells binding to the ECM proteins, collagen IV, laminin, fibronectin, and vitronectin and 40-75% binding to monolayers of fibroblasts, smooth muscle cells, and HT-29 cells. Treating mesenchymal cells with the fibrogenic cytokines, IL-1, IL-4, or TNF-alpha, which increase production of ECM proteins, did not alter binding of HT-29 cells to these monolayers. Attachment of HT-29 cells to cell monolayers was inhibited by cytochalasin D and sodium azide, but not cycloheximide or neuraminidase. Attachment to ECM proteins, in contrast, was unaffected by any of these metabolic inhibitors but required certain divalent cations (Mg2+ and Mn2+ but not Ca2+). Antibody to the integrin beta 1, chain (CD29) eliminated binding to collagen and laminin but not to fibronectin, fibroblasts, and HT-29 monolayers. Antibody to the vitronectin receptor inhibited binding to fibronectin. Antibodies to integrin alpha 1-alpha 6 chains had no effect on any adhesion event. Three colon cancer cell lines were tested for expression of VLA antigens: alpha 2 and alpha 3 were detected on all three, alpha 1 and alpha 6 were variably expressed, while alpha 4 and alpha 5 were absent. This study demonstrates that several mechanisms account for tumor cell attachment to substratum and cells.

Costimulation of the CD3 pathway by CD28 ligation in human intestinal lymphocytes

A distinctive characteristic of human intestinal lymphocytes is their low responsiveness to stimuli of the CD3 pathway in vitro. This may be due to anergy resulting from CD3 stimulation without costimulation. Costimulatory molecules, such as HML-1, VLA-4, CD44, and CD28, may be lacking or unresponsive to ligation. Expression of these costimulatory markers was examined by immunofluorescent staining and flow cytometry. Their ability to costimulate intestinal lymphocytes was tested by measuring changes in proliferation, IL-2 production, and calcium ion mobilization. HML-1 was found on 87 +/- 8% of intraepithelial lymphocytes but only 52 +/- 10% of lamina propria lymphocytes; the density of expression was three times higher on the former. VLA-4 and CD44 were expressed on more than 80% of both lymphocyte types. CD28 was found on 31 +/- 26% of intraepithelial lymphocytes and 55 +/- 15% of lamina propria lymphocytes; virtually all CD4+ T cells and 15 to 26% of CD8+ T cells were CD28+. Of the four costimulatory molecules, ligation of only CD28 increased proliferation and IL-2 production; none affected calcium ion mobilization with stimulation through the CD3 pathway. The marker B7/BB1, a binding partner to CD28, was not present on lymphocytes or epithelial cells by flow cytometry. CD28 is the only one of these costimulatory molecules that enhanced CD3-induced functions of both intestinal lymphocyte types, but little ligand is available in vivo. Without coligation, CD3 activation may lead to anergy.

Human intestinal intraepithelial lymphocytes bind to mucosal mesenchymal cells through VLA4 and CD11A

Human intestinal intraepithelial lymphocytes (IEL), predominantly CD8+ T lymphocytes, are uniquely situated at the basolateral surfaces of epithelial cells in contact with the myofibroblasts that comprise the basement membrane. Since mesenchymal cells may anchor IEL in this location and may also serve as antigen-presenting cells, the mechanism of binding to IEL was investigated. Lymphocytes were radiolabeled with [51Cr] sodium chromate, cocultured with mesenchymal cell monolayers, and the nonadherent lymphocytes removed by washes. Those adherent to the monolayers were counted by measuring the amount of radiolabel retained in the well. A large fraction of IL-2-activated IEL bound to KD (lip fibroblast), HISM (jejunal smooth muscle), and JF (jejunal fibroblast) cell lines after a 2-hr incubation: 33 +/- 11, 37 +/-14, and 48 +/- 15%, respectively. When monoclonal antibodies directed at the alpha chains of the very late activation antigens (CD49) were added alone or combined with anti CD11a to assays measuring IEL binding to KD or JF monolayers, the greatest inhibition (33 to 38%) occurred with anti-alpha 4 combined with anti-CD11a. The majority of IEL expressed alpha 1 and alpha 4 before and after a 3-day culture with IL-2, with no change in surface density. VCAM-1, a binding partner to alpha 4, was not expressed on KD or JF cells, and anti-VCAM antibody had no effect on binding. In summary, alpha 4 and CD11a on IEL mediate binding to mesenchymal cells.

Human intestinal intraepithelial lymphocytes have potent chemotactic activity

BACKGROUND & AIMS

Inflammation is created by the movement of leukocytes toward soluble attractants (chemokines). The aim of this study was to identify the chemokines that attract intestinal lymphocytes.

METHODS

Intraepithelial and lamina propria lymphocytes were isolated from human jejunal mucosa of healthy individuals and cultured in interleukin (IL) 2 for 3 days. Migration was assessed using the Boyden transwell assay. Increases in cytoplasmic calcium ion concentration ([Ca2+]i) were measured from changes in fluorescence in Fura-2-loaded lymphocytes on exposure to the cytokines.

RESULTS

A large number of intraepithelial lymphocytes migrated toward IL-8 and RANTES (regulated on activation, normal T cell expressed and secreted), and a small number migrated toward IL-10. In contrast, only a few lamina propria lymphocytes migrated toward IL-8, and none responded to the other chemokines tested. The chemokines IL-8 and IL-10, but not RANTES, increased [Ca2+]i in intraepithelial lymphocytes; this calcium mobilization was not affected by ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid, indicating that calcium is released from intracellular sources. None of the factors caused calcium mobilization by lamina propria lymphocytes.

CONCLUSIONS

This study shows that intraepithelial lymphocytes have greater migratory and calcium-mobilizing activity than lamina propria lymphocytes and that these two activities do not correlate with each other.

Interleukin-7 activates intestinal lymphocytes

Human intestinal lymphocytes, particularly intraepithelial lymphocytes, proliferate minimally to some agents, like mitogens and stimuli of the CD3 pathway. This in vitro finding may be due, in part, to a loss of factors found in vivo. Three T-cell growth factors, IL-7, IL-9, and IL-12, were tested for their ability to stimulate the proliferation of intestinal lymphocytes. Both intraepithelial lymphocytes and lamina propria lymphocytes proliferated more vigorously to IL-7 than to IL-9 or IL-12, and only IL-7 increased stimulation through the CD3 pathway. The IL-7-induced response was IL-2-dependent: IL-2 receptors appeared on both intestinal lymphocyte types, and antibody to the IL-2 receptor blocked IL-7-induced proliferation. Both CD4+ and CD8+ T-cell subsets responded to this cytokine as shown by phenotype-depletion experiments and constancy in the CD4/CD8 ratios after culture with IL-7. In addition, the T-cell receptor alpha beta and gamma delta subsets responded equally well to IL-7. This newly described selective proliferative response of intestinal lymphocytes to IL-7, but not to IL-9 or IL-12, requires no preactivation and may enhance growth in vivo.

Pitfalls in the characterization of small intestinal lymphocytes

The morphological characteristics of human intestinal lymphocytes may vary depending upon whether they are examined in tissue sections or after isolation. This study uncovered some causes of these discrepancies. The majority of intraepithelial lymphocytes (IEL) and lamina propria lymphocytes (LPL) are of the same size and granularity as peripheral blood mononuclear cells (PBMC), negating the idea that most IEL are large granular lymphocytes. LPL were previously shown to express markers of early activation by flow cytometry but not by immunohistochemistry. This study shows that it is the low density of surface antigen expression that explains this discrepancy: only the highly sensitive flow cytometric analysis can detect such low-density expression. Previous reports of intestinal macrophage and B cell numbers and functions vary markedly. This may be due to variable amounts of contamination with epithelial cells (EC) that lose their characteristic columnar appearance and cytoplasmic mucin upon isolation. They share many features of macrophages (such as morphology and binding to plastic and latex beads) but lack phagocytic ability and superoxide generation, explaining, perhaps, the wide variation in the reported functions of presumed intestinal macrophages. In addition, a large fraction of EC non-specifically strain with anti-immunoglobulin antibodies. Their contamination of intestinal lymphocyte preparations accounts for the discrepancy in B cell numbers identified by surface immunoglobulin expression versus B cell markers. Intestinal lymphocytes do indeed differ in many ways from circulating lymphocytes, but investigators must be attentive to factors that may artifactually alter their results.

Distinct structural and functional epitopes of the alpha E beta 7 integrin

Intestinal intraepithelial lymphocytes (iIEL) are predominantly CD3+, CD8+ T lymphocytes located above or adjacent to the mucosal basement membrane. Although they are positioned to interact with intercellular luminal antigen or with enterocytes, the function of iIEL remains unknown. Most (> 85%) of the iIEL express the alpha E beta 7 integrin which appears to be involved in the adhesion of lymphocytes to epithelial cells. We report the characterization of three monoclonal antibodies (mAb) termed alpha E7-1, alpha E7-2, and alpha E7-3, that react with the alpha E beta 7 integrin recognized by the previously described mAb HML-1 as demonstrated by identical sodium dodecyl sulfate-polyacrylamide gel electrophoresis mobility and charge. Flow cytometric analysis of antibody cross-blocking indicated that these mAb recognize distinct epitopes of alpha E beta 7. While all of the mAb were capable of blocking the adhesion of cultured iIEL to a breast epithelial cell line, only HML-1 and alpha E7-1 (which recognize an identical or closely related epitope) were co-stimulatory with suboptimal concentrations of anti-CD3 mAb in inducing proliferation of cultured iIEL. Thus, these mAb appear to recognize functionally distinct epitopes of alpha E beta 7 and will be useful to study relationships between the structure and function of this integrin.

Distribution of dominant T cell receptor beta chains in human intestinal mucosa

The majority of human intestinal intraepithelial lymphocytes (iIELs) are CD8+ T cells that use the T cell receptor (TCR)-alpha/beta. Previous studies have shown that iIELs isolated from segments of small intestine or colon contain one or several dominant alpha/beta T cell clones. It is not known whether these clones expand only locally in response to a particular antigen or whether they are widely distributed throughout the intestine. To address this question, iIELs were purified from near the proximal and distal margins in a series of intestinal resections for noninflammatory diseases. TCR-beta expression was then assessed by semiquantitative polymerase chain reaction amplification, analysis of N-region length, and DNA sequencing. The previously described oligoclonal expansion of iIELs was confirmed in each sample. Identical dominant clones were identified in the proximal and distal samples from most cases, including samples taken from sites as distant as the transverse and sigmoid colon or rectum. Distinct clones were found in only one case with samples from the terminal ileum and transverse colon. These results demonstrate that a relatively small number of widely dispersed T cell clones comprise the majority of cells in the human intestinal mucosa.

Intestinal mucosal lymphocytes have H1 receptors: H1 antagonists reduce their proliferation and cytotoxicity

Histamine and H1 antagonists inhibit the proliferation and natural killer activity of peripheral blood mononuclear cells, which express large numbers of H1 receptors. This study examined the presence of H1 receptors and the effects of histamine, H1 antagonists (pyrilamine and diphenhydramine), and H2 antagonists (cimetidine and ranitidine) on human intestinal lymphocyte proliferation and cytotoxicity. Intestinal lymphocytes were obtained by chemical and enzymatic treatment of surgical specimens and purified by Percoll density gradient centrifugation. Proliferation was measured by [3H]thymidine incorporation of mitogen-stimulated lymphocytes; cytotoxicity was measured by the standard 51Cr-release assay using HT-29 adenocarcinoma target cells. Scatchard analysis of radioligand binding using [3H]pyrilamine demonstrated H1 receptors. The mitogen-induced proliferative responses of intraepithelial lymphocytes and lamina propria lymphocytes were inhibited by histamine and the H1 antagonists but not the H2 antagonists. Cytotoxic activities of fresh or IL-2-stimulated mucosal lymphocytes (spontaneous and lymphokine-activated killing, respectively) were also reduced by the H1 antagonists. A large number of H1 receptors were found on intraepithelial lymphocytes and peripheral blood mononuclear cells and still more on lamina propria lymphocytes. Intestinal lymphocytes bear H1 receptors; histamine and H1 antagonists have immunomodulatory effects on these cells.

Spontaneous cytotoxicity of intestinal intraepithelial lymphocytes: clues to the mechanism

Human intestinal intraepithelial lymphocytes (IEL) demonstrate target cell-restricted spontaneous cytotoxic (SC) activity that is due to CD2+CD3+CD8+CD16-CD56- effector cells; they kill epithelial cell (EC) tumours (such as DLD-1 colon cancer cells), but not natural killer (NK)-sensitive K-562 cells. The present study shows that the measured levels of SC activities by IEL correlated with those of autologous lamina propria lymphocytes (LPL), but not with those of peripheral blood lymphocytes (PBL). Also, the susceptibilities of DLD-1 cell clones to lysis by IEL and PBL effector cells did not correlate, suggesting different mechanisms of lysis. Antibody blocking experiments showed that the main surface molecules involved in lysis depended on the effector cell type: alpha E beta 7 (HML-1) on IEL and CD16 on PBL. No antibody-dependent cell-mediated cytotoxicity (ADCC) was demonstrated by IEL, even after stimulation with interferon-gamma (IFN-gamma). Few IEL expressed Fc receptors for IgG. This study describes further differences between the SC activities of IEL and PBL.

T-cell activation in human intestinal mucosa: the role of superantigens

BACKGROUND

Superantigens are a class of potent T-cell mitogens that activate T cells using specific antigen receptor V regions. Superantigens have been implicated in the pathogenesis of several autoimmune diseases, including inflammatory bowel disease. The present study examines the role of superantigens in the human gastrointestinal immune response.

METHODS

Human intestinal epithelial cells and T lymphocytes were obtained from surgical specimens and cultured in the presence or absence of exogenous superantigens. Activation of T cells and V region usage were measured by thymidine incorporation and by cell staining using a panel of monoclonal antibodies.

RESULTS

Neither epithelial cells from normal nor diseased intestinal mucosa expressed virally encoded, endogenous superantigens. However, 50% of epithelial cell preparations could present exogenous bacterial superantigens to T cells. In the other 50%, a defect in this function was observed, which did not represent production of suppressive factors or absence of accessory cytokines. Mucosal T lymphocytes proliferated in response to superantigens in vitro, expressing increased transferrin receptor, interleukin-2 receptor, and HLA-DR.

CONCLUSIONS

A superantigen-driven mucosal immune response may occur in health and in chronic inflammatory states. The intestinal epithelial cell may mediate this response, through presentation of superantigens to mucosal T lymphocytes.

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.

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.

Intestinal intraepithelial lymphocytes bind to colon cancer cells by HML-1 and CD11a

Human intraepithelial lymphocytes (IEL), predominantly CD8+ T-lymphocytes located between intestinal epithelial cells (EC), may represent the first-line immune defense against colon cancer. The mechanism by which IEL bind to the colon cancer line, DLD-1, was evaluated. A larger fraction of IEL than peripheral blood mononuclear cells bound to DLD-1 monolayers (25 +/- 16 versus 8 +/- 4% binding, P < 0.05). Binding increased when DLD-1 monolayers were incubated with interferon-gamma but not with tumor necrosis factor-alpha. Similar numbers of IEL adhered to EC tumors, HT-29 and 5637, and the non-EC tumor, A375, but fewer bound to nonmalignant smooth muscle (HISM) and fibroblast (KD) lines (P < 0.01). Binding of IEL to DLD-1 was reduced by monoclonal antibodies to HML-1 and CD11a (47 +/- 9 and 26 +/- 13% inhibition, respectively) and was completely eliminated by both combined (93 +/- 4% inhibition). Anti-HML-1 also inhibited the binding of IEL to other EC tumors but did not affect binding to non-EC tumors or fibroblasts. To conclude, the binding of IEL to EC tumors is mediated by HML-1 and CD11a [A. I. Roberts, S. M. O'Connell, and E. C. Ebert. Binding of intraepithelial lymphocytes to colon cancer cells is mediated by HML-1 and LFA-1 (abstract). Gastroenterology, 102: A685, 1992].

Do the CD45RO+CD8+ intestinal intraepithelial T lymphocytes have the characteristics of memory cells?

Human intraepithelial lymphocytes (IEL) are predominantly CD45RO+ (memory) CD8+ T lymphocytes located between intestinal epithelial cells. This study determines whether IEL share other characteristics with circulating CD45RO+ lymphocytes. Memory cells are large and have an upregulated expression of adhesion molecules. In contrast, the majority of IEL are the same size as peripheral blood (PB) T cells. In addition, IEL do not have an increased density of adhesion molecules, although a larger percentage express CD54 and CD58 compared to PBL. Allo-CTL activity, demonstrated by CD45RO+ PBL, could not be shown using either IEL or lamina propria lymphocytes (LPL) after a 5-day culture with alloantigen. However, after a 2.5-week culture with allogeneic PBL and interleukin-2 (IL-2), both IEL and LPL were capable of this cytotoxic function. The addition of IL-4 or IL-6 did not alter CTL activity by mucosal lymphocytes. Alloantigen-stimulated IEL, LPL, and PB CD8+ T cell lines were propagated for up to 16 weeks. All lines demonstrated alloantigen-specific proliferation. The PB CD8+ T lymphocytes maintained their phenotype and allo-CTL activity. In contrast, the CD4+ subset in the IEL and LPL became the predominant lymphocyte type and demonstrated potent lytic activity that was not alloantigen specific. This study shows that (1) IEL do not have increased density of adhesion molecules, (2) mucosal lymphocytes demonstrate allo-CTL activity, (3) CD8+ T cells in the mucosa cannot be perpetuated long-term by alloantigen and IL-2, and (4) mucosal CD4+ T cell lines demonstrate marked alloantigen-nonspecific cytotoxicity. The only characteristic shared by IEL and circulating memory cells is allo-CTL activity.

Ulcerative colitis serum recognizes the M(r) 40K protein on colonic adenocarcinoma cells for antibody-dependent cellular cytotoxicity

Antibodies in ulcerative colitis (UC) serum promote antibody-dependent cellular cytotoxicity (ADCC) against colon cancer cells. The target molecules on the cells recognized by the antibody are unknown. This study examines the role of the M(r) 40K colon epithelial protein in this process. Serum from 29 UC patients, but not from 19 patients with Crohn's disease, significantly (p < 0.001) induced more cytotoxicity than did normal serum against DLD-1 colon cancer cells which are known to express the M(r) 40K protein. Peripheral blood lymphocytes but not polymorphonuclear leukocytes showed ADCC. Anti-M(r) 40K monoclonal antibodies significantly (p < 0.001) inhibited the UC-serum-induced ADCC, but not the spontaneous cytotoxicity. These results suggest the involvement of the M(r) 40K protein in ADCC induced by UC serum.

Lymphokine-activated killing by human intestinal lymphocytes

Human intraepithelial lymphocytes (IEL), predominantly CD8+ T lymphocytes located between intestinal epithelial cells, may represent the first-line host defense against colon cancers. This study evaluates their lymphokine-activated killer (LAK) activity and compares it to that of lamina propria lymphocytes (LPL). The phenotypes of the precursor or effector LAK cells were determined by depleting IEL or LPL of specific subsets using antibody and complement lysis either before or after a 7-day culture with interleukin-2 (IL-2), respectively, and then measuring changes in lytic activity. The precursor and effector LAK cells in the IEL were mixed populations with some but not all expressing CD2, CD3, CD8, and NKHl. The LAK activity by LPL was due to CD2+CD3+CD4-CD8- precursor cells and CD8+ effector cells. Since the IEL LAK cells were heterogeneous, their lytic activity against two different target cell types was analyzed. The LAK activity against DLD-1 colonic adenocarcinoma cells was reduced by antibodies to CD2, CD11a, and HML-1, whereas LAK activity against K-562 cells was reduced by antibodies to CD2, CD11a, and CD54, but not HML-1, indicating a target-cell-specific mechanism. Cold competition experiments, however, showed that the same cytotoxic IEL bound to both target cells. In conclusion, LAK activity by IEL is due to a mixed population, whereas that by LPL is due to CD8- precursor cells and CD8+ effector cells. The same effector LAK IEL kill both DLD-1 and K-562 targets, but different mechanisms are involved.

Human lymphocytes lack substance P receptors

Substance P (SP), a neuropeptide found in high concentrations in the gut, is reported to have many potent immunomodulatory actions. This study evaluated some effects of SP on human peripheral blood lymphocytes (PBL) and jejunal intraepithelial lymphocytes (IEL) and the expression of SP receptors on these and other lymphocytes types. In contrast to previous studies, SP (10(-8) or 10(-12) M) did not affect the proliferation (spontaneous or mitogen-induced) nor spontaneous cytotoxicity by PBL or IEL. To determine whether this unresponsiveness was due to an absence of SP receptors, the SP binding potential of these and other human lymphocyte types was determined by Scatchard analysis of radioligand binding. The IM-9 B lymphoblastoid cell line, used as a positive control, demonstrated 4838 +/- 603 or 3131 +/- 832 receptors per cell, with a Kd of 0.21 +/- 0.01 or 0.18 +/- 0.09 nM, using [3H]SP or 125I-SP, respectively. No receptors were found on PBL, polymorphonuclear leukocytes, splenocytes, IEL, or jejunal lamina propria lymphocytes using either radioligand. These findings dispute the presence of large numbers of SP receptors on lymphocytes in peripheral blood, spleen, or intestinal mucosa, and argue against any major effect of SP on T cell proliferation or spontaneous cytotoxicity.

Spontaneous cytotoxicity of human intraepithelial lymphocytes against epithelial cell tumors

Human intraepithelial lymphocytes are T cells primarily of the CD8+ phenotype located between intestinal epithelial cells. The cytotoxic and suppressor activities of these lymphocytes are largely unexplored. The spontaneous cytotoxic activity of these cells is evaluated in this study. Jejunal intraepithelial lymphocytes spontaneously lysed a variety of epithelial cell tumor lines (colonic and pancreatic adenocarcinomas and bladder epidermoid carcinoma) but not the highly natural killer-sensitive K-562 cells. Cold target inhibition studies showed that these lymphocytes preferentially bind the DLD-1 colonic adenocarcinoma cells rather than the K-562 cells. Pretreatment of the effector cells with interferon-gamma did not change their cytotoxic activity. The cytotoxic cells are T lymphocytes (expressing CD2, CD3, and CD8). In contrast, the spontaneous cytotoxic activity of peripheral blood lymphocytes is directed against both epithelial cell targets and K-562 cells, is enhanced by interferon-gamma, and is effected by natural killer cells (expressing CD2, CD16, and NKH1). Thus, the spontaneous cytotoxicity of intraepithelial lymphocytes differs from that of peripheral blood lymphocytes in their target cell restriction, lack of response to interferon gamma, and effector cell phenotype. Lymphocytes in the intestinal epithelium may have a novel and important role in recognizing and destroying transformed epithelial cells and colon cancers.

Oligoclonal expansion and CD1 recognition by human intestinal intraepithelial lymphocytes

A human intestinal intraepithelial lymphocyte (IEL) T cell line was established from jejunum to characterize the structure and function of the alpha beta T cell antigen receptors (TCRs) expressed by this population. Single-sided polymerase chain reaction (PCR) amplification cloning and quantitative PCR amplification of the TCR chains from the cell line and from fresh IELs demonstrated that IELs were oligoclonal. The IEL T cell line exhibited CD1-specific cytotoxicity and a dominant IEL T cell clone was CD1c-specific. Thus, human jejunal intraepithelial lymphocytes are oligoclonal and recognize members of the CD1 gene family.

Human intraepithelial lymphocytes. Immunomodulation and receptor binding of vasoactive intestinal peptide

This study evaluates the immunomodulation and receptor binding of vasoactive intestinal peptide on human peripheral blood lymphocytes and intraepithelial lymphocytes. Vasoactive intestinal peptide (VIP, 10(-8) and 10(-12) M) had no effect on the concanavalin A-induced proliferation or the spontaneous cytotoxicity against K-562 targets by either lymphocyte type. Human peripheral blood lymphocytes had a mean of 927 vasoactive intestinal peptide receptors per cell with a Kd of 1.12 x 10(-10) M, as demonstrated by the competitive displacement of [125I]peptide by unlabeled peptide using Scatchard analysis. In contrast, intraepithelial lymphocytes had no high-affinity receptors as shown by the negligible binding of 50 pM [125I]VIP. Peptide binding by peripheral blood lymphocytes, although reduced by exposure to dithiothreitol and ethylenediamine tetraacetic acid, was still greater than binding by intraepithelial lymphocytes. As intraepithelial lymphocytes are mainly CD8+ T cells, the possibility that this phenotype may not bind VIP at all was tested by specifically depleting peripheral blood lymphocytes by antibody and complement lysis. Peripheral blood lymphocytes expressing CD8, CD4, and/or CD2 were responsible for most of the binding, indicating that CD8+ T lymphocytes in the peripheral blood and in the intestinal epithelium differ in their capacity to bind VIP.

Induction of suppressor cells by Mycobacterium paratuberculosis antigen in inflammatory bowel disease

We studied the M. paratuberculosis-induced proliferation and suppressor cell generation by peripheral blood lymphocytes from patients with inflammatory bowel disease. Peripheral blood lymphocytes were separated from 33 patients with Crohn's disease, 18 with ulcerative colitis, nine with other intestinal diseases, and five with autoimmune disorders. Proliferation of peripheral blood lymphocytes from normal individuals in response to 10 micrograms/ml of M. paratuberculosis antigen was reduced by depletion of CD4+ T cells. The ability of M. paratuberculosis antigen to suppress concanavalin A-induced proliferation (expressed as a percentage suppression) was reduced by depletion of CD8+ T cells. This suppression was the same whether peripheral blood lymphocytes were from normal individuals, patients with intestinal diseases other than inflammatory bowel disease, or patients with autoimmune disorders (47 +/- 14%, 44 +/- 24%, and 30 +/- 26%, respectively). In contrast, the suppression induced by M. paratuberculosis for patients with Crohn's disease and ulcerative colitis (66 +/- 22% and 67 +/- 22%) was much greater than that for normal individuals (P less than 0.001). In particular, lymphocytes from patients with active Crohn's disease demonstrated little proliferation in response to this antigen but marked suppressor activity (79 +/- 13%). How the immunomodulatory effects of this antigen relate to the pathogenesis of the inflammatory bowel diseases remains to be determined.