Immunological studies in patients with Crohn's disease.

An investigation of immunological parameters was conducted in 38 patients with Crohn's disease. The immunological tests employed included skin tests with dinitrochlorobenzene and a battery of common skin test antigens, lymphocyte transformation with phytohaemagglutinin and pokeweed mitogen, serum immunoglobulins, and absolute lymphocyte counts. Crohn's disease patients were divided into two groups, those treated with immunosuppressive drugs and those not receiving immunosuppressive medications. The latter group was subdivided into patients with active and inactive disease. Immunosuppressed patients with Crohn's disease did not develop sensitivity to dinitrochlorobenzene and had mildly depressed skin test reactivity to common skin test procedures. Non-immunosuppressed patients with active Crohn's disease also reacted less frequently to common skin test antigens, but 16 of 17 such patients developed sensitivity to dinitrochlorobenzene. Lymphocyte transformation with phytohaemagglutinin and pokeweed mitogen was normal in all groups of patients with Crohn's disease. However, when suboptimal incubation periods were used with phytohaemagglutinin stimulation, there was a significant difference between Crohn's disease patients and controls. Serum immunoglobulin levels and absolute lymphocyte counts were normal in all Crohn's disease patients. We conclude that immunity in Crohn's disease is qualitatively normal.