HLA antigens and anti-neutrophil cytoplasmic antibodies (ANCA) in inflammatory bowel disease

Hypothesis and objectives: the hypothesis of this study is that genes involved in the regulation of the immune system, expressed by HLA antigens and anti-neutrophil cytoplasmic antibodies (ANCA), could be determinants of disease susceptibility and behavior in inflammatory bowel disease (IBD). Material and method: seventy patients with a diagnosis of inflammatory bowel disease, 46 with ulcerative colitis and 24 with Crohn's disease were included. HLA class I (A and B) and II (DR) antigens were studied by serological techniques. Detection of ANCA was carried out in all patients by an indirect immunofluorescence method. The relative frequencies of HLA antigens were compared with a control group made up of 156 blood donors. The control group for the ANCA study was made up of 100 individuals. Results: we found a significant increased frequency of HLA-DR2 in patients with ulcerative colitis. No significant differences were found between patients with Crohn's disease and controls regarding HLA typing. We detected a significant increase of HLA-DR3 in extensive forms of ulcerative colitis. Detection of ANCA was positive in 46% of the patients with ulcerative colitis and in 12% of the patients with Crohn's disease (p < 0.05). We observed an increased frequency of ANCA in patients with UC and HLA-DR2 (p = 0.15). Conclusions: the association found between HLA-DR3 and extensive forms of ulcerative colitis provides evidence of genetic heterogeneity. The relationship between ANCA and HLA phenotype (although not significant) supports this concept.