Spontaneous suppressor cell activity in the peripheral blood of patients with malignant and chronic inflammatory bowel diseases.

Fifteen patients with colorectal tumours, 15 patients with Crohn's disease (CD) and two groups of normal controls were investigated for the presence of spontaneous suppressor cell activity (SSCA) in peripheral blood mononuclear cells (PBMC). In comparison to the age and sex matched controls patients with colorectal carcinoma exhibited a significant increase in SSCA (P less than 0.01). No evidence could be obtained that the suppressive effect was due to a soluble factor such as prostaglandins. In contrast, patients suffering from CD presented a decreased SSCA. No correlation was obtained between the enhanced SSCA in tumour patients and the clinical stage of the disease, levels of oncofetal antigens or serum immune complexes. Likewise in patients with CD no correlation was found between decreased SSCA and CD index or different serum parameters. When PBMC of the different test groups were incubated with histamine or cimetidine before they were added to the indicator system the suppressive activity remained unchanged. Also pre-incubation of normal PBMC with alpha-fetoprotein or carcinoembryonic antigen did not change the spontaneous suppressor cell activity. Whether the significantly enhanced in vivo activity of spontaneous suppressor cells in patients with colorectal carcinoma is one of the multifactorial mechanisms leading to the establishment of cancer or whether it rather represents a reflection of the immune system on colorectal tumour antigens remains unsolved.