Enhanced peripheral blood T-cell cytotoxicity in inflammatory bowel disease

NK cells are biologic and biochemical targets of 6-mercaptopurine in Crohn's disease patients

NK cells, which contribute to immune defense against certain viral infections and neoplasia, are emerging as modifiers of chronic immunologic diseases including transplant rejection and autoimmune diseases. Immunobiology and genetic studies have implicated NK cells as a modifier of Crohn's disease, a condition often treated with thiopurine agents such as 6-mercaptopurine (6-MP). Here, we demonstrate that thiopurines mediate NK cell apoptosis via a caspase 3 and 9 inclusive pathway, and that this process is triggered by thiopurine-mediated inhibition of Rac1. We also show that CD patients in clinical remission maintained on 6-MP have decreased NK cell Rac1 activity, and decreased NK cell numbers in their intestinal biopsies. These observations suggest that thiopurine targeting of NK cells may be a previously unappreciated therapeutic action of these agents in IBD.

γ/δ T Cells are not Involved in the Natural and Antibody-Dependent Cytotoxicity of Peripheral blood Mononuclear Cells in Inflammatory Bowel Disease

In a previous study, we showed an imbalance in the cytotoxic phenotype of circulating PBMC of IBD patients, possibly related to an alteration in the cytotoxic activity, which might play a role in the immunopathogenesis of IBD. γ/δ T cells, which are increased in the PBMC of IBD patients, represent a minor population of peripheral lymphocytes displaying cytolytic potential and showing both MHC and non-MHC cytotoxicity. This study was performed in order to verify their role in the cytotoxic activity of PBMC from IBD patients and correlate this activity to UC and CD, respectively. We observed a decreased NK cytotoxicity of PBMC in both UC and CD patients and this findings was unrelated to γ/δ T lymphocytes. In fact, both total and γ/δ-depleted PBMC of IBD patients, showed comparable lytic activity. On the contrary, the ADCC lytic activity was within normal range in our patients, ad was not modified by removal of γ/δ cells. The increase of Vδ1+ T cells, previously observed in our patients, seems to be unrelated to this functional impairment, because of a low cytotoxic activity displayed by this subset. Alternatively, the expanded Vδ1+ T cells could be involved in the pathogenesis of the autoimmune phenomena observed in IBD, by a mechanism different from cytotoxicity, such as autoantibodies production and/or loss of tolerance.

Genetic dissection of the cellular pathways and signaling mechanisms in modeled tumor necrosis factor-induced Crohn's-like inflammatory bowel disease

Recent clinical evidence demonstrated the importance of tumor necrosis factor (TNF) in the development of Crohn's disease. A mouse model for this pathology has previously been established by engineering defects in the translational control of TNF mRNA (Tnf(Delta)(ARE) mouse). Here, we show that development of intestinal pathology in this model depends on Th1-like cytokines such as interleukin 12 and interferon gamma and requires the function of CD8(+) T lymphocytes. Tissue-specific activation of the mutant TNF allele by Cre/loxP-mediated recombination indicated that either myeloid- or T cell-derived TNF can exhibit full pathogenic capacity. Moreover, reciprocal bone marrow transplantation experiments using TNF receptor-deficient mice revealed that TNF signals are equally pathogenic when directed independently to either bone marrow-derived or tissue stroma cell targets. Interestingly, TNF-mediated intestinal pathology was exacerbated in the absence of MAPKAP kinase 2, yet strongly attenuated in a Cot/Tpl2 or JNK2 kinase-deficient genetic background. Our data establish the existence of redundant cellular pathways operating downstream of TNF in inflammatory bowel disease, and demonstrate the therapeutic potential of selective kinase blockade in TNF-mediated intestinal pathology.

HLA class-I-restricted and colon-specific cytotoxic T cells from lamina propria lymphocytes of patients with ulcerative colitis

We established cytotoxic T-lymphocyte (CTL) lines against colonic epithelial cell line from LPLs of patients with ulcerative colitis by continuous stimulation with human lymphocyte antigen A (HLA-A) matched colonic epithelial cell lines and clones from LPLs using polyclonal stimulation with phytohemagglutinin. The established CTL lines and clones showed cytotoxicity against HLA-A-matched colonic epithelial cell line but not against HLA-mismatched colonic epithelial cell lines, and HLA-A-matched lung and esophagus cell lines. The CTL response was HLA class I-restricted and mediated by CD8-positive T-lymphocytes. Moreover, the CTL line showed cytotoxicity against autologous B-LCLs pulsed with peptides extracted from HLA-A-matched colonic epithelial cell line but not against other organ-derived peptides pulsed and unpulsed autologous B-LCLs. CTL lines and clones established from LPLs of patients with ulcerative colitis showed colon-specific and HLA class I-restricted killing of human colonic epithelial cell line, suggesting that these CTLs may play a role in colonic epithelial cell damage in some patients with ulcerative colitis.

Generation of MHC class I-restricted cytotoxic T cell lines and clones against colonic epithelial cells from ulcerative colitis

We established CTL lines and clones against colonic epithelial cells from PBLs of patients with ulcerative colitis by continuous stimulation with HLA-A locus-matched colonic epithelial cell lines. We developed a nonradioactive europium release cytotoxicity assay to detect CTLs. PBLs from 3 of 12 patients but not from any of 14 normal controls who shared at least one haplotype of HLA-A locus with two colonic epithelial cell lines, CW2 and ACM, showed increased cytotoxicity against these lines. Three CTL lines established from the PBLs of patients showed increased cytotoxicity against HLA-A locus-matched CW2 or ACM but not against matched lung or esophagus cell lines. The phenotypes of CTL lines were alpha beta-TCR+ CD3+ CD8+ CD16-. The CTL line MS showed increased cytotoxicity against freshly isolated colonic epithelial cells but not against cells with a different HLA-A locus. Two CTL clones were generated from MS and clone 3-2, expressing CD3+ CD8+ CD4- CD56-, showed high MHC class I-restricted cytotoxicity against the colonic epithelial cells. These results indicated that CTLs against colonic epithelial cells may contribute to epithelial cell damage in ulcerative colitis.

Ulcerative colitis: an immunological disease?

Ulcerative colitis is an inflammatory disease of the large intestine of unknown aetiology. The nature of the inflammatory infiltrate together with the response to corticosteroids suggests that an abnormal immune response is at work. The key question of whether the immune system is responding to an abnormal breach in the mucosa due to another primary abnormality or whether the primary defect lies within the immune response itself has not been answered. Thus far, it is clear that both T and B cell compartments are involved in the persistence of inflammation but the initial interactions that take place in the mucosa in terms of antigen processing and presentation have not been adequately investigated. Those critical steps and potential defects that push T cells and B cells into a heightened state of activation need to be identified.

Analysis of germline and expressed T cell receptor variable region genes in Crohn's disease

A possible role of the T cell receptor genes in the pathogenesis of Crohn's disease was investigated by 1) comparison of restriction fragment length polymorphisms at the T cell receptor beta chain locus in 64 Crohn's patients and 64 normal controls; 2) semi-quantitative polymerase chain reaction analysis of T cell receptor beta and alpha chain variable region gene expression by lamina propria lymphocytes from resected segments of diseased terminal ileum. We found no association between any of the restriction fragment length polymorphisms and Crohn's disease using polymorphic markers spanning the T cell receptor beta chain locus. Analysis of T cell receptor V beta and V alpha gene expression showed that expression of T cell receptor V region families in terminal ileum lymphocytes from patients with active Crohn's disease was indistinguishable from the lymphocytes found in normal terminal ileum. These data fail to support susceptibility to Crohn's disease being associated with the T cell beta chain antigen receptor genotype. No restricted or dominant T cell receptor variable region gene expression was found in Crohn's disease tissue, compared to normal terminal ileum.

Cytotoxic activity of V beta 8+ T cells in Crohn's disease: the role of bacterial superantigens

In Crohn's disease, disease-related stimuli could alter the T cell receptor (TCR) repertoire. To examine the possibility that changes in function may occur in T cell subsets without obvious changes in expression of TCR, we analysed the TCR repertoire of cytotoxic T lymphocytes in Crohn's disease peripheral blood. Furthermore, we examined the effect of bacterial superantigens, staphylococcal enterotoxin B (SEB) and E (SEE) on the cytotoxic function of T cell subsets bearing different TCR V genes using MoAbs specific for CD3 and TCR V gene products in a redirected cytotoxicity assay. There was no difference between patients and controls in the cytotoxicity measured in concanavalin A (Con A)-stimulated peripheral blood mononuclear cells (PBMC) with anti-CD3 or with six of seven anti-TCR V gene MoAbs. However, the cytotoxicity of V beta 8 T cells was decreased in Crohn's disease patients. This was not due to a decrease in total or CD8+ T cells expressing V beta 8. Furthermore, in normal subjects, PBMC stimulation with SEE and SEB selectively expanded and increased the cytotoxicity of V beta 8 and V beta 12 T cells, respectively. In Crohn's disease, although SEB stimulation increased the number and cytolytic function of the V beta 12 subset, SEE stimulation failed to increase cytolytic activity of V beta 8+ T cells in spite of the expansion of V beta 8+ T cells. These results suggest that the changes in cytotoxic function observed in V beta 8 T cells in Crohn's patients may reflect previous exposure to a V beta 8-selective superantigen.

Phenotypic and functional characterization of T-cell lines generated from colonoscopic biopsy specimens in patients with ulcerative colitis

Intestinal T-cell lines were generated from lamina propria mononuclear cells isolated from colonoscopic biopsies in ulcerative colitis patients and controls. In both ulcerative colitis and controls, expanded cells were constituted largely by T-cell receptor alpha beta+, CD4+, CD45RA- (helper), and CD8+, CD11b- (cytotoxic) phenotypes. T-cell receptor V beta gene usage was not significantly changed after cell expansion and no difference was observed between ulcerative colitis and controls. Ulcerative colitis cells, especially those derived from the patients with long-standing disease, showed significantly higher levels of cytotoxicity against the target cells, including those of colonic epithelial origin, and enhanced production of tumor necrosis factor-alpha and interferon-gamma after short incubation with anti-CD3 antibody. Generation of T-cell lines from colonoscopic biopsy specimens may be useful for detailed functional characterization of locally infiltrating T cells in ulcerative colitis patients.

Depressed T cell reactivity to recall antigens in Crohn's disease before and after surgical resection

Earlier studies regarding possible primary immune disturbances participating in the pathogenesis of Crohn's disease yielded conflicting results. Peripheral blood lymphocyte subsets and lymphocyte proliferative responses to five soluble recall antigens and to the polyclonal stimulator phythaemagglutinin were therefore measured in 17 patients with active Crohn's disease, before and six months after surgical resection of the inflamed intestine and in 16 healthy controls. Lymphocyte proliferation in response to all five recall antigens was significantly lower in patients than in controls. No significant differences with controls were detected after surgery. Addition of indomethacin to phythaemagglutinin stimulated lymphocyte cultures had a stronger proliferation enhancing effect in patients than in controls, resulting in comparable proliferative responses in both groups. When both indomethacin and prostaglandin E2 were added, inhibition of reactivity by prostaglandin E2 was stronger in patients' cultures. This suggests a higher sensitivity to inflammatory prostaglandins in Crohn's disease. The degree of lymphocyte stimulation by antigens correlated positively with the percentage of circulating memory T cells (CD 45 RA-). The percentage of activated (HLA-DR+) CD8 cells was higher in patients than in controls. The CD4/CD8 ratio, which was not significantly different between patients and controls, correlated significantly with disease activity and characteristics, even in the postoperative phase. These findings suggest that immune abnormalities in Crohn's disease fluctuate with and are probably secondary to inflammatory activity.

T cell cytotoxicity of autologous and allogeneic lymphocytes in a patient with Crohn's disease

We report a 27-year-old male with Crohn's disease (CD) of the small and large intestine, whose peripheral blood lymphocytes (PBL) showed increased cell-mediated cytotoxicity (CTL). Autologous and allogeneic effector cells from PBL and intestinal lymph nodes (LN) were isolated on a Ficoll-Hypaque gradient. Colonic cells were prepared as the target and were incubated for 6h with effector cells, after being labeled with Na(2)51CrO4. The CTL activity [effector/target (E/T) ratio, 100:1] of PBL for autologous targets was increased by 38% compared with that in normal subjects (< 10%), while that shown by LN was not increased (14%). The CTL activity of allogeneic PBL prepared from three of four other CD patients was also increased. Anti-major histocompatibility (MHC) class I and II and CD4 and CD8 monoclonal antibodies (50 micrograms/ml) significantly inhibited CTL activity. Complement-mediated depletion of CD2+ cells significantly reduced CTL activity. These results suggest that MHC-restricted CTL may play a role in mucosal damage in some patients with Crohn's disease.

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.

Major histocompatibility antigen-restricted cytotoxicity in inflammatory bowel disease

BACKGROUND

The role of cytotoxicity mediated by peripheral blood mononuclear cells for colonic epithelial cells in inflammatory bowel disease (IBD) is still controversial. To clarify it, we studied major histocompatibility antigen (MHC)-restricted T cell-mediated cytotoxicity (CTL).

METHODS

Cytotoxicity was measured by 51Cr release from colonic cells after the 6-hour incubation with peripheral blood mononuclear cells in 11 IBD patients (6 with Crohn's disease and 5 with ulcerative colitis).

RESULTS

CTL activity (E/T ratio = 200:1 or 100:1) for autologous target cells was significantly increased (22%-40%) in 5 of 6 CD and 4 of 5 UC patients (22%-64%) compared with that for allogeneic target cells. The increase in CTL activity was mainly inhibited by anti-MHC class I and CD8 monoclonal antibodies (50 micrograms/mL), while it was partially inhibited by anti-MHC class II or CD4 antibodies in some patients. Complement-mediated depletion of CD2+ cells also significantly decreased CTL activity.

CONCLUSIONS

The results indicate that MHC-restricted T cell cytotoxicity may play a role in mucosal damage in some patients of IBD.

Peripheral expansion of gamma delta T cell receptor-positive cells in a patient with Crohn's disease

A 13 year old boy with Crohn's disease had a prominent expansion (over 40%) of gamma delta T cell receptor-positive cells (gamma delta T cells) in the peripheral blood. The gamma delta T cells were gradually decreased from 48 to 22% in 18 months. Anti-gamma delta T cell receptor-triggered cytotoxicity was evident at onset and after 1 year. The significance of peripheral expansion of gamma delta T cells in a patient with Crohn's disease is discussed.

Anti-CD2 and anti-CD3 induced T cell cytotoxicity of human intraepithelial and lamina propria lymphocytes

The effector function of immunocompetent cells in the gut mucosa has not yet been defined. The cytotoxic function of these cells might be important in the normal immune response and could be relevant to the mucosal damage seen in inflammatory conditions. The cytotoxic function of isolated intraepithelial and lamina propria mononuclear cells in six and 18 hour assays after the addition of various stimuli that interact with the human leukocyte antigens CD2 and CD3 on the mucosal effector cells was investigated. T cell phenotypes were determined using CD4, CD8, and HML1 to characterise cells of the appropriate compartments. Anti-CD3 and phytohaemagglutinin can induce toxic activity of lamina propria lymphocytes in most individuals after six hours and in all individuals after 18 hours. Anti-CD2, anti-CD3, and phytohaemagglutinin are similarly effective at triggering lamina propria lymphocytes. Intraepithelial lymphocytes contain predominantly CD8 and HML1 positive T cells, differentiating phenotypically intraepithelial lymphocytes from lamina propria lymphocytes. Intraepithelial lymphocytes are not cytotoxic at six hours, but have a toxic function comparable with lamina propria lymphocytes after 18 hours with all three triggers. Intraepithelial lymphocytes from inflamed mucosa (Crohn's disease and diverticulitis) mediate significantly reduced cytotoxicity in vitro compared with normal mucosa, whereas lamina propria lymphocyte toxicity is not different. Reduced numbers of cytotoxic cells and reduced reactivity to the trigger substances used after in vivo activation or cold target inhibition could explain the observed differences between intraepithelial lymphocytes from inflamed and uninflamed mucosa. Changes in cell mediated cytotoxicity of intraepithelial lymphocytes and lamina propria lymphocytes may be involved in the mucosal damage in these inflammatory conditions.

Subset markers of CD8(+) cells and their relation to enhanced cytotoxic T-cell activity during human immunodeficiency virus infection

Using fresh whole blood or isolated lymphocytes, the activity of in vivo generated cytotoxic T-lymphocytes (CTL) was measured as the OKT3-specific lysis of HL-60 targets, in a cross-sectional study of 53 HIV (+) patients. CTL activity in the entire HIV(+) group was two to three times higher than in HIV(-) controls, with WHO stage 3 (=pre-AIDS) patients showing the highest cytolytic function. The whole-blood CTL assay was validated and its practical and theoretical advantages are discussed. Within the CD8(+) cells, the number and proportion of the CD45RO(+) "memory" subset were significantly increased in HIV(+) subjects. The HLA-DR(+) subset rose most spectacularly in the asymptomatic stage of the infection, while the CD38(+) subset was the only one still significantly rising between the pre-AIDS and the AIDS stage. CTL activity was most closely correlated with T8 cells expressing the CD38 marker. In the context of CTL, CD38 thus seems to reflect activation rather than immaturity. Lymphocytes from HIV(+) subjects with a high OKT3-specific lytic capacity also destroyed normal lymphoblasts to a significant extent, pointing to their possible involvement in an autodestructive process. Our data thus suggest the importance of T8 cytolytic function and/or T8 subtyping in the immunopathogenesis and the prognosis of HIV infection.

Sulfasalazine inhibits the binding of TNF alpha to its receptor

Sulfasalazine was found to exhibit a dose-dependent inhibition of human mucosal and peripheral blood cytotoxic T-cell function. The drug also inhibited the cytotoxic activity of supernatants from anti-CD3-triggered T-cells against murine L929 fibroblasts. TNF alpha has previously been shown to be primarily responsible for the lytic activity of such supernatants and this was confirmed. Sulfasalazine also inhibited the lytic activity of recombinant TNF alpha. When tested under conditions where TNF alpha was allowed to bind to but not lyse the target cells, the results suggested that the drug inhibits the action of this cytokine by inhibiting its binding to the cell membrane receptor. Additional evidence for an inhibitory effect of sulfasalazine on the membrane binding of TNF alpha was obtained by demonstrating a dose-dependent displacement of 125I-TNF alpha from HL60 cells. Although sulfasalazine is often considered to be a pro-drug for site-specific delivery of its component fragments 5-ASA and sulfapyridine, the results demonstrate an immunopharmacological property of the parent compound that is not shared with its component molecules.

Evidence for circulating activated cytotoxic T cells in HIV-infected subjects before the onset of opportunistic infections

The activity of both cytotoxic T lymphocyte (CTL) and natural killer (NK) cells were measured cross-sectionally in 43 subjects seropositive for HIV, in 27 HIV- blood donors and in 24 HIV- persons from the Outpatients Clinic for sexually transmitted diseases. CTL activity was evaluated using the HL-60 cells coated with OKT3 as the targets and freshly separated peripheral blood lymphocytes as the effectors. In 20 out of 43 HIV+ subjects, CTL activity was significantly enhanced in comparison to the HIV- subjects. This lytic activity correlated positively with the percentages of CD3+ HLA-DR+, of CD8+ CR3- and of CD57+ CD16- lymphocytes, and was greatly reduced after elimination of CD8+, of HLA-DR+ or of CD57+ cells. The median CTL activity seemed to increase from CDC group II to CDC group IV (Centers for Disease Control classification), but to return back to control levels in those patients with a history of opportunistic infections. NK function in HIV+ subjects was not significantly different from that in the blood donors. In seropositive patients, NK activity correlated positively with the percentages of both CD16+ CD57+ and of CD8+ CR3+ cells and was strongly diminished after elimination of CD16+ or of CD57+ cells. There was no significant change in NK function according to the clinical stage. The data show that circulating CD8+ HLA-DR+ CD57+ T cells in HIV+ subjects are activated cytotoxic T cells and point to progressive (over) activation of this T cell compartment until the onset of opportunistic infections.

The CD8+ Leu-7+ subset of T cells in Crohn's disease: distinction between cytotoxic and covert suppressor functions

An expanded T cell subpopulation (CD8+ Leu-7+) has previously been reported in the peripheral blood of patients with Crohn's disease. This subpopulation of T cells was associated with a 'covert suppressor' function, particularly in patients with mild/early Crohn's disease, suppressing immunoglobulin production in vitro when cultured in the presence of pokeweed mitogen. T cells with the same CD8+ Leu-7+ phenotype have also been shown to exhibit non-major histocompatability complex-restricted cytotoxicity when triggered by anti-CD3 antibodies, and this cytotoxic activity has also been shown to be elevated in patients with Crohn's disease. Because cytotoxic cells can have immunoregulatory properties, we investigated the possible relationship between the cytotoxic and 'covert suppressor' functions of the CD8+ Leu-7+ subset of T lymphocytes in patients with mildly active Crohn's disease. Although the correlation between T cell cytotoxic activity and the CD8+ Leu-7+ cells was confirmed, no evidence for covert suppressor activity was found; there were no significant differences between the amount of IgM secreted by B cells from normal subjects and patients with Crohn's disease when cultured with T cells at increasing T:B ratios. In addition, IgM production by peripheral blood B cells did not correlate with either the number of CD8+ Leu-7+ cells or with the level of cytotoxic T cell activity. Furthermore, when B cells and CD4+ T cells were co-cultured with increasing numbers of CD8+ T cells, there was no evidence for excessive suppressor T cell activity in Crohn's disease. Although some patients exhibited low levels of IgM production, this was due to diminished B cell function, rather than excessive T suppressor activity or defective T helper activity. We conclude that the CD8+ Leu-7+ T cell subset is associated with cytotoxic but not with enhanced or covert suppressor activity in Crohn's disease. The previously described covert suppressor function attributed to cells with this phenotype in Crohn's disease was not found to account for diminished B cell responsiveness in vitro and is unlikely to be of major pathophysiologic significance in the majority of patients.