Immunological studies in patients with Crohn's disease

Inflammatory bowel diseases in patients with adaptive and complement immunodeficiency disorders

Crohn's disease and ulcerative colitis are idiopathic chronic inflammatory diseases that primarily affect the gastrointestinal tract. The underlying causes remain poorly understood, but there is a growing body of evidence advocating a likely primary pathogenic role for immunodeficiency in the development of Crohn's lesions. Concordantly, a number of congenital immunodeficiencies disrupting the cellular innate immune system strongly predispose to noninfectious, Crohn's-like inflammatory bowel disease. There are case reports and series suggesting that the same may be true for some of the congenital adaptive and complement immunodeficiencies. This review considers and critiques these potential associations.

Immunoresponsiveness in ulcerative colitis and Crohn's disease--effect of colectomy and suppression of disease activity

We evaluated the effect of medically induced symptomatic disease improvement on in vitro tests of cell-mediated immune responses in 33 patients with Crohn's disease. When results obtained in 17 patients with ulcerative colitis were compared with those of 10 patients with ulcerative colitis who had undergone a colectomy, no significant correlation was detected between individual clinical and laboratory variables or the Crohn's disease activity index and in vitro tests of cell-mediated immunity. A different pattern emerged from the longitudinal tests of cell-mediated immunity: when these test results were initially abnormal in patients with Crohn's disease, clinical improvement as assessed by the Crohn's disease activity index was associated with normalizing cell-mediated immunity. In contrast, when the test results were initially normal, clinical improvement was not associated with any change in the immune response. Following colectomy in patients with ulcerative colitis, some abnormalities of suppressed immune responses remained, although patients were cured of their disease. Factors other than clinical disease activity may be responsible for the suppressed immunoresponsiveness in some patients with inflammatory bowel disease, and variable changes in cell-mediated immunity occur after both surgical and medical treatment.

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.

Alteration in T lymphocyte subpopulations in inflammatory bowel disease

Peripheral blood mononuclear cells from thirty-one patients with inflammatory bowel disease (ulcerative colitis and Crohn's disease) were analysed for the proportions and absolute numbers of total T cells, and for the T cell subpopulations carrying Fc receptors for either IgM (Tmu cells) or IgG (T gamma cells). Twenty-six control subjects were studied simultaneously. Total T cell numbers were normal in patients with inflammatory bowel disease but there was a marked reduction in the proportion and absolute numbers of Tmu cells in patients, whether their disease was active or in remission. T gamma cells were normal. Simultaneous assessment of lymphocyte response to mitogens in vitro was performed in a group of patients. Responses to phytohaemagglutinin, concanavalin A and pokeweed mitogen were decreased and a positive correlation was found between the number of circulating Tmu cells and the responses to mitogens in vitro. These studies demonstrate that despite the presence of normal numbers of total T cells in inflammatory bowel disease, there is a marked imbalance in T cell subpopulations that correlates with mitogen responsiveness. This imbalance provides a possible cellular basis for the defect in cell-mediated immunity seen in these patients.

Isolation and purification of human large bowel mucosal lymphoid cells: effect of separation technique on functional characteristics

Human large bowel lamina propria lymphoid cells have been isolated using both mechanical and enzymatic techniques. Their separation from other cell types after isolation was effected with greater efficiency by sedimentation on isokinetic gradients than by filtration through glass bead columns. After being purified, the capacity of the lamina propria lymphocytes to function in vitro as effector cells in antibody-dependent cellular cytotoxicity was determined. Mechanical distruption of the mucosa gave low yields of lymphoid cells, which lacked the capacity for cytotoxicity. Enzymatic digestion of mucosal tissue, by comparison, yielded large numbers of viable lymphoid cells which retained a significant level of cytotoxic activity. Investigation revealed that mechanical homogenisation stimulated the synthesis of prostaglandin E2, and inhibitor studies showed that this mediator was responsible for the lack of cytotoxic activity in mechanically-liberated lymphocytes.

[The immune competence of patients with Crohn's disease (author's transl)]

The cell-mediated and humoral immune responses were assessed in 15 patients with Crohn's disease and in 28 age-matched control subjects by means of several in vivo and in vitro methods. The disease activity in most patients was absent or moderate. Studying cellular immunocompetence we investigated the skin reactivity to various recall antigens (Candida, Trichophytin, Mumpsantigen, Streptokinase-Streptodornase, PPD), the primary immune response to Dinitrochlorobenzene (DNCB) and Keyhole Limpet Hemocyanin (KLH), and the lymphocyte transformation induced by mitogens (Phytohemagglutinin, Concanavaline A, Pokeweed Mitogen) and specific antigens. Humoral immunity was studied by measuring immunoglobulins, isohemagglutinins, and the antibody response to KLH. In addition, complement components and (in 10 patients) the proportions of T- and B-lymphocytes in the peripheral blood were evaluated. Cutaneous responsiveness to Candida, Mumps-antigen, SK-SD, and DNCB as well as the cellular immune response to KLH were impaired in patients with Crohn's disease (significance was reached for SK-SD, DNCB, and the mean area of induration). The lymphocyte transformation test with PHA, ConA, and PWM revealed normal results. For specific antigens (PPD, SK-SD, KLH) a good correlation could be demonstrated between delayed hypersensitivity and the in vitro lymphocyte responsiveness. Humoral immunity was not unequivocally impaired in Crohn's disease. Five patients with Crohn's disease proved constantly decreased total absolute lymphocyte counts in peripheral blood. The proportions of T- and B-lymphocytes and the complement-levels were corresponding to those in normal controls. No correlation was found between immunological and clinical parameters. In conclusion, patients with Crohn's disease exhibited a partial impairment of the cellular immune response, whereas humoral immunity was not affected. However, it remains to be elucidated whether this immune defect represents a basic pathogenetic factor in the onset of the disease.

In vitro testing of immunoresponsiveness in patients with inflammatory bowel disease: prevalence and relationship to disease activity immunoresponsiveness in IBD

Abnormalities in the numbers and function of thymus and function of thymus-derived and bone marrow-derived lymphocytes (T and B cells) and K cells were determined in sixty-nine consecutive patients with Crohn's disease or ulcerative colitis. Rosetting techniques to identify subpopulations of lymphocytes showed a significant decrease in E-rosettes (T cells) and significant increase in EA- and EAC-rosettes (B cells) in patients with inflammatory bowel disease when compared to normals. In vitro lymphocyte transformation responses to mitogens and antigens were depressed to a variable degree. Mean levels of K cell activity were not significantly different from normal controls. A considerable degree of individual variation was noted in all groups. When the results of each groups were considered, none of the laboratory variables correlated with the site, duration or activity of disease, therapy, presence of iron deficiency anemia, weight loss or hypoalbuminaemia. Thus, in vitro evidence of abnormal immune responses in patients with inflammatory bowel disease cannot be directly related to clinical or laboratory variables and probably reflects a multi-factorial aetiology.

Chasing Crohn's

The importance of Crohn's disease in oral pathology is briefly discussed. A series of experiments using immunofluorescent tracing techniques is described which culminates in the identification of a Crohn's-specific circulating antibody which reacts with autologous oral mucosa in vitro. It is suggested that this forms the basis of a diagnostic test.

Crohn disease. Newer aspects of etiology, diagnosis and therapy

Images

The effect of azathioprine on cell-mediated immunity (CMI) to Candida albicans in Crohn's disease

Using as antigen a suspension of Candida albicans, strain A, three tests of cell-mediated immune reactivity (delayed skin hypersensitivity, lymphocyte stimulation and leucocyte migration inhibition) were undertaken in patients with Crohn's disease to determine the effect of azathioprine given as the sole anti-inflammatory medication. No significant effect was demonstrable on 48 hr induration in the skin test. Uptake of thymidine by lymphocytes in vitro, whether spontaneous or antigenically induced, was greater during azathioprine treatment than before it. The assumption that this finding might be associated with clinical recovery was confirmed in antigen-stimulated cultures by the fact that, irrespective of treatment, patients who had been able to resume their normal occupations showed markedly higher reactivity than those who were still disabled (P<0·002). It was also found that azathioprine treatment in itself potentiated lymphocyte stimulation by C. albicans. The range of values for inhibition of leucocyte migration was the same in the treated and untreated groups, but certain individuals displayed a substantial change in reactivity when re-tested after institution or discontinuation of azathioprine treatment. Untreated patients with Crohn's disease did not differ from normal subjects in their cell-mediated reactivity to C. albicans. The increased rate of thymidine uptake by lymphocytes from patients receiving azathioprine is discussed in the light of recent hypotheses linking virus-induced malignancy with lymphoblastic transformation.

Evidence for a transmissible factor in Crohn's disease

The injection of rabbits' ileum with homogenates of both normal and Crohn's affected human bowel tissue gave Crohn's-like changes in 11 of 27 animals after six months, but 12 months after injection the rabbit bowel had reverted to normal. The addition of ampicillin to the homogenates prevented the appearance of these Crohn's-like changes in 12 out of 12 rabbits. These results are interpreted as providing evidence for a transmissible factor present in both normal and Crohn's affected bowel in the aetiology of Crohn's disease.