Background: The membrane bound receptor OX40 (CD134) - a member of the TNF-R/NGF-R superfamily - is expressed on activated CD4+-T cells in humans and rodents. The interaction of OX40 with its ligand (OX40L) has been shown to be important in T-cell dependent B cell-stimulation and T-cell costimulation in vitro and in vivo. Several studies in experimental animal models for immunologically mediated GI-diseases have stressed the important role of the OX40-OX40L interaction for their manifestations. To assess if the OX40-OX40L interaction is also crucial in the pathogenesis of immunologically mediated diseases of the human gastrointestinal tract (e.g. celiac disease, Crohn's disease, ulcerative colitis) we investigated, in a first line of experiments, the expression of OX40 in biopsy specimens of patients suffering from these diseases.
Methods: The biopsies were formalin fixed and paraffin-embedded and cut into 5 microm slides. To demask the antigen, the slides were consecutively cooked in citrate buffer for 20 min. Binding of anti-OX40 antibody was detected using the alkaline phosphatase-anti-alkaline phosphatase (APAAP) method.
Results: Nine of 11 biopsy specimens of patients with celiac disease were OX40-positive; none of the 20 control duodenal biopsies demonstrated OX40-positivity; and all biopsies of patients with ulcerative colitis (n = 11) or Crohn's disease (n = 11), respectively, stained positively for OX40. One of the 20 control biopsies showed OX40 staining.
Discussion: OX40 is highly expressed in the gastrointestinal tissue of patients with immunologically mediated bowel diseases. Together with previous studies in animal models for these diseases, the present results point to a potential role of OX40 in their pathogenesis.