Defective suppression in the autologous mixed lymphocyte reaction in patients with Crohn's disease

Expression of nonclassical class I molecules by intestinal epithelial cells

It is well recognized that the nature of the immune response is different in the intestinal tract than in peripheral lymphoid organs. The immunologic tone of the gut-associated lymphoid tissue is one of suppression rather than active immunity, distinguishing pathogens from normal flora. Failure to control mucosal immune responses may lead to inflammatory diseases such as Crohn's disease (CD) and ulcerative colitis (UC) and celiac disease. It has been suggested that this normally immunosuppressed state may relate to unique antigen-presenting cells and unique T-cell populations. The intestinal epithelial cell (IEC) has been proposed to act as a nonprofessional antigen-presenting cell (APC). Previous studies have suggested that antigens presented by IECs result in the activation a CD8(+) regulatory T-cell subset in a nonclassical MHC I molecule restricted manner. We therefore analyzed the expression of nonclassical MHC I molecules by normal IECs and compared this to those expressed by inflammatory bowel disease (IBD) IECs. Normal surface IEC from the colon and, to a much lesser extent, the small bowel express nonclassical MHC I molecules on their surface. In contrast, mRNA is expressed in all intestinal epithelial cells. Surface IEC express CD1d, MICA/B, and HLA-E protein. In contrast, crypt IECs express less or no nonclassical MHC I molecules but do express mRNA for these molecules. Furthermore, the regulation of expression of distinct nonclassical class I molecules is different depending on the molecule analyzed. Interestingly, IECs derived from patients with UC fail to express any nonclassical MHC I molecules (protein and HLA-E mRNA). IECs from CD patients express HLA-E and MICA/B comparable to that seen in normal controls but fail to express CD1d. Thus, in UC there may be a failure to activate any nonclassical MHC I molecule restricted regulatory T cells that may result in unopposed active inflammatory responses. In CD only the CD1d-regulated T cells would be affected.

Antigen induced suppression in peripheral blood and lamina propria mononuclear cells in inflammatory bowel disease

Using an autologous system, suppressor cell function to a range of mycobacterial antigens and Kunin antigen of peripheral blood mononuclear cells and lamina propria lymphocytes has been investigated in normal subjects and patients with inflammatory bowel disease. In the peripheral blood there was reduced antigen induced suppression in patients with Crohn's disease in remission to Mycobacterium paratuberculosis, purified protein derivative (PPD), M fortuitum, and Kunin antigens (p less than 0.05). In patients with ulcerative colitis in remission there was reduced antigen induced suppression in the peripheral blood to Kunin antigen (p less than 0.001), M avium (p less than 0.01), M nonchromogenecin, and M fortuitum (p less than 0.05). The phenomenon of antigen induced suppression was largely CD8 dependent, as depleting CD8+ cells reduced the effect and the concentration of soluble CD8 in the culture supernatant was directly related to the suppressor index (r = 0.25, p less than 0.05). These results are likely to be a true reflection of the cell mediated response to antigen as patients with a positive Mantoux skin test have a significantly higher suppressor index to PPD than Mantoux negative subjects (p less than 0.05). These findings may have significance in the aetiopathogenesis of inflammatory bowel disease. However, a similar effect could not be shown in the lamina propria lymphocytes of patients having colectomy for active disease.

Blood transfusion and recurrent Crohn's disease

The effect of blood transfusion on the postoperative recurrence of Crohn's disease has been investigated. Clinical and pathological data from 197 patients treated by right hemicolectomy between 1947 and 1988 have been analysed. Symptomatic recurrences confirmed radiologically or histologically have been recorded and cumulative recurrence rates calculated for transfused and non-transfused patients. Perioperative blood transfusion does not influence the development of recurrent disease (log rank test, chi 2 = 0.112).