Studies of peripheral blood lymphocytes in Crohn's disease. Circulating activated T cells

Deficit of gammadelta T lymphocytes in the peripheral blood of patients with Crohn's disease

BACKGROUND

Gammadelta T lymphocytes are an important component of innate immunity. Previous studies have shown their role in the development of Crohn's-like colitis in mice.

AIMS

The aim of this study was to measure the γδ T lymphocyte levels in Crohn's disease (CD) patients.

METHODS

A prospective study of 40 patients with CD compared with 40 healthy subjects (control group) matched by age and sex was undertaken. Lennard-Jones criteria were used for the diagnosis of CD. Disease activity was measured with the Crohn's disease activity index (CDAI). New patients, patients in remission, and patients with active disease were evaluated. Lymphocytic populations of CD3+, CD4+, CD8+, CD56+, CD19+, and αβ and γδ subsets were measured in the peripheral blood of all participants.

RESULTS

The levels of CD3+, CD4+, CD8+, and CD19+ lymphocytes were decreased in CD patients compared with the control group (P = 0.002, 0.049, 0.003, and 0.023, respectively). Although both γδ and αβ T lymphocytes were lower in patients with CD, γδ T subsets showed the lowest levels in CD patients (mean 0.0259 × 10(9)/l) versus healthy controls (mean 0.0769 × 10(9)/l), P < 0.001. In particular, γδ CD8+ T subsets (mean 0.0068 × 10(9)/l) had the largest difference compared to the control group (mean 0.0199 × 10(9)/l), P = 0.008.

CONCLUSIONS

There is a decrease in the global lymphocyte population in the peripheral blood of patients with CD compared to healthy controls. This decrease is more evident in γδ T lymphocytes, especially γδ CD8+ T subsets. Our conclusion is that these results support the theory that a complex alteration of immune responses that affects the total numbers and function of γδ T cells is present in CD.

IL-18-binding protein expression by endothelial cells and macrophages is up-regulated during active Crohn's disease

The pathogenesis of Crohn's disease (CD) remains under intense investigation. Increasing evidence suggests a role for mature IL-18 in the induction of proinflammatory cytokines and Th1 polarization in CD lesions. The aim of this study was to investigate the contribution of the IL-18-neutralizing (a and c) and non-neutralizing (b and d) isoforms of IL-18-binding protein (IL-18BP) during active CD. Intestinal endothelial cells and macrophages were the major source of IL-18BP within the submucosa, and this IL-18BP production was also found to be relevant to other types of endothelial cells (HUVEC) and macrophages (peripheral monocytes). IL-18BP messenger transcript and protein were significantly increased in surgically resected specimens from active CD compared with control patients, correlating with an up-regulation of IL-18. Analysis of the expression of the four IL-18BP isoforms as well as being free or bound to IL-18 was reported and revealed that unbound IL-18BP isoforms a and c and inactive isoform d were present in specimens from active CD and control patients while isoform b was not detected. IL-18/IL-18BP complex was also detected. Interestingly, although most was complexed, free mature IL-18 could still be detected in active CD specimens even in the presence of the IL-18BP isoform a/c. These results demonstrate that the appropriate neutralizing isoforms are present in the intestinal tissue of patients with active CD and highlights the complexity of IL-18/IL-18BP biology.

Bioactive IL-18 Expression Is Up-Regulated in Crohn’s Disease

An imbalance of immunoregulatory factors is believed to contribute to uncontrolled mucosal Th1 cell activation in Crohn’s disease (CD). IL-18, a macrophage-like cell-derived cytokine, is involved in Th1 clone development, and IFN-γ production. Therefore, IL-18 expression was investigated in CD. Whole mucosal intestinal tissue and lamina propria mononuclear cells (LPMC) of 12 CD and 9 ulcerative colitis (UC) patients and 15 non-inflammatory bowel disease (IBD) controls were tested for IL-18 by semiquantitative RT-PCR and Western blot analysis. Transcripts for IL-18 were found in all samples tested. However, increased IL-18 mRNA accumulation was detected in both mucosal and LPMC samples from CD in comparison to UC and controls. In CD, transcripts for IL-18 were more abundant in the mucosal samples taken from involved areas. An 18-kDa band consistent with mature IL-18 was predominantly found in CD mucosal samples. In mucosal samples from non-IBD controls, IL-18 was present as a 24-kDa polypeptide. Consistently, active IL-1β-converting enzyme (ICE) subunit (p20) was expressed in samples from either CD or UC, whereas, in colonic mucosa from non-IBD controls, ICE was synthesized as precursor (p45) only. To confirm that IL-18 produced in CD tissue was functionally active, CD LPMC were treated with a specific IL-18 antisense oligonucleotide. In these cultures, IL-18 down-regulation was accompanied by a decrease in IFN-γ expression. In aggregate, our data indicate that IL-18 up-regulation is a feature of CD and suggest that IL-18 may contribute to the local immunoinflammatory response in CD.

Coexpression of CD4 and CD8 on peripheral blood T cells and lamina propria T cells in inflammatory bowel disease by two colour immunofluorescence and flow cytometric analysis

Using two colour immunofluorescence with fluorescein isothiocyanate and phycoerythrin labelled monoclonal antibodies and multiparameter flow cytometry, we investigated the coexpression of CD4 and CD8 antigens on peripheral blood lymphocytes and lamina propria lymphocytes of patients with ulcerative colitis and Crohn's disease and normal control subjects. Both the absolute number and the proportion of peripheral blood CD4+, CD8+ cells in inflammatory bowel disease were small but significantly increased compared with those in normal control subjects. Peripheral blood lymphocytes activated with phytohaemagglutinin showed appreciably increased coexpression of CD4+, CD8+. These CD4, CD8 positive cells were large and granular. Thus the increased number of peripheral blood CD4+, CD8+ cells in inflammatory bowel disease suggests that chronic immune activation occurs not only in the active state of the disease but also in remission. The proportion of CD4+, CD8+ cells in the lamina propria was greater than in peripheral blood in normal subjects, suggesting chronic immune stimulation of the local immune system. This was also seen in patients with Crohn's disease or inactive ulcerative colitis. The proportion of CD4+, CD8+ cells was, however, significantly less in the lamina propria of patients with active ulcerative colitis. Whether this implies a possible defect in mucosal immunoregulation in active ulcerative colitis cannot be determined from these results.

Flow cytometric analysis of peripheral blood lymphocytes in ulcerative colitis and Crohn's disease

Using two colour immunofluorescence with fluorescein isothiocyanate and phycoerythrin labelled monoclonal antibodies, multi-parameter flow cytometry was used to examine the antigenic characteristics of peripheral blood lymphocytes in whole blood of patients with ulcerative colitis and Crohn's disease who were not taking immunosuppressive drugs. The numbers of CD4+ and CD8+ lymphocytes in patients with ulcerative colitis and Crohn's disease remained unchanged so that the CD4/CD8 ratio was the same as that of normal control subjects. In Crohn's disease there were many activated T cells (CD3+, CD25+). Although natural killer cells in active Crohn's disease were lower than in normal control subjects, cytotoxic T lymphocytes, as defined by CD3+, CD16+, did not differ in patients with inflammatory bowel disease compared with normal control subjects. For B cell subsets, there were differences in Leu-1+ B cells, Leu-8+ B cells, Fc epsilon R+B cells (Leu-16+, Leu-20+), and activated B cells (Leu-12+, Leu-21+) between patients with inflammatory bowel disease and normal control subjects. These differences are compatible with local activation of B cells in the inflamed colon.

Immune events associated with inflammatory bowel disease

Immunologic abnormalities have been implicated in the etiology of inflammatory bowel disease (IBD). Defects of systemic immunity and of local (intestinal) immunity have been studied. The numbers of T and B lymphocytes and their characteristics seem to vary with the disease, but no cause-and-effect relationship has been established. The presence of anticolon antibodies in patients with ulcerative colitis suggests that these antibodies could be involved in IBD, but they have also been found in other conditions. In the peripheral blood, abnormalities of cell-mediated immunity are inconsistent and suggest that they are not fundamental defects of the disease. The hypothesis that the inflammatory process is a result of immune-mediated intestinal tissue damage is being extensively studied. The high familial incidence of the disease suggests a role of histocompatibility locus antigens, but no reproducible association can be established. In vivo and in vitro studies of mucosal mononuclear cells have revealed abnormalities of immunoglobulin production, some types of cytotoxicity against gut-derived antigens, and altered lymphokine production associated with the disease. Further studies of the intestinal immune system would seem to be the most fruitful line of research.

Peripheral blood and portal tract lymphocyte populations in primary sclerosing cholangitis

The relative distribution of lymphocyte subpopulations in the blood and liver of patients with primary sclerosing cholangitis (PSC) and related diseases has been studied using immunoenzyme techniques. The peripheral blood CD4/CD8 T lymphocyte ratio was significantly higher in active ulcerative colitis (UC) and in PSC with inactive UC than in inactive UC alone. In contrast, no relationship with disease activity was seen in Crohn's disease. The portal tract t lymphocyte count per high power field (mean +/- S.D.) was higher in pre-cirrhotic PSC (173 +/- 105) and primary biliary cirrhosis (PBC: 210 +/- 110) than in histologically normal liver (42 +/- 27). However, the overall portal tract CD4/CD8 ratio was similar in PSC (1.49), PBC (1.89) and normal controls (1.63). The results are consistent with immunological involvement in the pathogenesis of PSC, but argue against the hypothesis that changes in the peripheral blood T cell subsets are due to sequestration at the site of tissue inflammation.

Crohn's disease and the mycobacterioses: a review and comparison of two disease entities

Crohn's disease is a chronic granulomatous ileocolitis, of unknown etiology, which generally affects the patient during the prime of life. Medical treatment is supportive at best, and patients afflicted with this disorder generally live with chronic pain, in and out of hospitals, throughout their lives. The disease bears the name of the investigator who convincingly distinguished this disease from intestinal tuberculosis in 1932. This distinction was not universally accepted, and the notion of a mycobacterial etiology has never been fully dismissed. Nevertheless, it was 46 years after the distinction of Crohn's disease and intestinal tuberculosis before research attempting to reassociate mycobacteria and Crohn's disease was published. Recently, there has been a surge of interest in the possible association of mycobacteria and Crohn's disease due largely to the isolation of genetically identical pathogenic Mycobacterium paratuberculosis from several patients with Crohn's disease in the United States, the Netherlands, Australia, and France. These pathogenic organisms have been isolated from only a few patients, and direct evidence for their involvement in the disease process is not clear; however, M. paratuberculosis is an obligate intracellular organism and strict pathogen, which strongly suggests some etiologic role. Immunologic evidence of a mycobacterial etiology, as assessed by humoral immune determinations, has been conflicting, but evaluation of the more relevant cellular immunity has not been performed. Data from histochemical searches for mycobacteria in Crohn's disease tissues have been equally conflicting, with acid-fast bacilli detected in 0 to 35% of patients. Animal model studies have demonstrated the pathogenic potential of isolates as well as elucidated the complexity of mycobacterial-intestinal interactions. Treatment of Crohn's disease patients with antimycobacterial agent has not been fully assessed, although case reports suggest efficacy. The similarities in the pathology, epidemiology, and chemotherapy of Crohn's disease and the mycobacterioses are discussed. The issue is fraught with controversy, and the data generated on the association of mycobacteria and Crohn's disease are in their infantile stages so that a general conclusion on the legitimacy of this association cannot be made. While no firm evidence clearly implicates mycobacteria as an etiologic agent of Crohn's disease, the notion is supported by suggestive and circumstantial evidence and a remarkable similarity of Crohn's disease to known mycobacterial diseases.

Quantitative immunological differences between newly diagnosed Graves' disease patients and relapsed patients

Class 2-positive T cells, T-cell and mononuclear cell subsets, thyrotropin receptor antibodies (TRAb) and immune complexes were evaluated in 34 newly diagnosed Graves' patients and in 13 relapsed patients before a cycle of specific medical treatment. Class II-positive T lymphocytes were detected by monoclonal antibodies against different epitopes of class II antigens, whereas 4F2-positive cells were detected by 4F2 monoclonal antibody. 4F2-positive cells were statistically increased in newly diagnosed Graves' patients compared to relapsed patients (p less than 0.05). An increased percentage of class II activated T cells, detected by monoclonal antibodies L243, was found in newly diagnosed patients in comparison with relapsed subjects (p less than 0.025). Newly diagnosed Graves' patients showed a significant decrease in the ratio suppressor/cytotoxic T cells in comparison with normal control subjects but not with relapsed patients. Ninety-one % of newly diagnosed Graves' patients showed a high TRAb value, whereas only 69% of relapsed patients showed increased values (p less than 0.025). No difference was observed in the immune complex positivity between newly diagnosed Graves' patients and relapsed subjects. In conclusion, both humoral and cellular immune differences were found in relapsed patients vs newly diagnosed Graves' patients. The immunological abnormalities are quantitatively more pronounced in the latter group.

Activated Fc alpha T cells in Crohn's disease are involved in regulation of IgA

Activated peripheral T cells (APT) of patients with Crohn's disease (CD) have been analysed for the expression of IgA-Fc receptors and for competence of IgA regulation. It was found that within the subset of APT an increased number of cells express binding sites for IgA (IgA-Fc), that was not found in other diseases with elevated numbers of APT. Moreover the number of IgA-Fc receptor expressing T cells was found to be increased in the inflamed mucosa too. Cocultures with autologous B cells revealed that isolated IgA-Fc receptor bearing T cells of patients with CD suppress IgA secretion. These data support the hypothesis that APT are involved in the immunopathogenesis of CD.

Lymphocyte subpopulations, lymphoblast transformation activity, and concanavalin A-induced suppressor activity in patients with ulcerative colitis and Crohn's disease

The following immunologic in vitro tests were applied on peripheral blood mononuclear cells (PBMC) from patients with chronic inflammatory bowel disease (IBD): concanavalin A (Con A)-induced suppressor test, Con A-activated lymphoblast transformation test, and spontaneous lymphoblast transformation test. Concomitant phenotypic characterization of subsets of PBMC was performed with monoclonal antibodies. Patients with ulcerative colitis and a control group with rheumatoid arthritis showed significantly reduced activity in the Con A-activated lymphoblast transformation test compared with healthy controls and patients with Crohn's disease. The distribution of PBMC subsets and the results of the other in vitro tests were similar for patients with IBD and healthy controls. Thus the decrease in Con A-activated lymphoblast activity was not due to an increased suppressor function as measured either by functional Con A-induced suppressor test or indirectly by T8 phenotype.

Activation of peripheral blood and intestinal lamina propria lymphocytes in Crohn's disease. In vivo state of activation and in vitro response to stimulation as defined by the expression of early activation antigens

In the present study the state of activation of either peripheral blood and intestinal lamina propria mononuclear cells in Crohn's disease was defined by investigating the expression of early activation antigens (namely the 4F2 antigen, the transferrin receptor and the interleukin-2 receptor). The expression of 4F2 and T9 antigens was greatly increased--in the peripheral blood and in the intestinal lamina propria whereas the proportion of interleukin-2 receptor bearing cells was much less pronounced. The counts of early activation antigens bearing cells in the lamina propria were quite comparable with those of the autologous peripheral cells. In the peripheral blood counts of 4F2 and T9 positive cells were very high in patients with active Crohn's disease but patients with quiescent disease also had a significantly raised proportion of 4F2 and T9 bearing cells. Only in those patients with no evidence of macroscopic disease (namely those resected without recurrence) the counts of early activation antigens bearing cells were within the normal range. The in vitro mitogen induced expression of early activation antigens on either peripheral and intestinal mononuclear cells of patients with Crohn's disease proved to be both quantitatively and qualitatively similar to that of the controls showing the full expression of 4F2, transferrin receptor, and interleukin-2 receptor. While demonstrating that in Crohn's disease there was no intrinsic defect of generation and expression of growth factors receptors by peripheral and intestinal lymphocytes, these results showed that there was a divergence in the expression of early activation antigens in vivo and in vitro. This would indicate that in Crohn's disease there is an in vivo increased population of preactivated rather than fully activated lymphocytes consisting of 4F2 and T9 bearing cells. The high proportion of these cells in the peripheral blood and in the intestine suggests that a chronic immune activation is present in these patients outside as well as within the affected bowel.

Immunology of inflammatory bowel disease

Although the aetiology of ulcerative colitis and Crohn's disease remain unknown, immunological effector mechanisms become activated within the inflamed mucosa and may be responsible for the pathogenesis of chronic disease. There is an increased production of immunoglobulin within the mucosa, some of which has specificity for bacterial antigens, and complement activation occurs during exacerbation of the disease. Lymphocytes isolated from peripheral blood, or from the intestinal mucosa, are cytotoxic to colonic epithelial cells in vitro; a reaction which can be modulated by serum factors and bacterial antigens. Within the mucosa, there are increased populations of T lymphocytes although there is no change in the ratio of helper- to suppressor-cells as defined by phenotype. Studies of immunoregulatory control have shown that there may be alterations in the modulation of the local immune response, especially during active disease, although it is not clear whether these changes are primary or merely secondary to inflammation. It is posulated that many of the humoral and cellular responses to gut-associated antigens occur as a result of increased antigen absorption, increased presentation of antigen to the immune system due to the expression of Class II antigens by the inflamed epithelium and altered immuno-regulatory control.