Suppressor cells, which might be activated in patients with gastric carcinoma, were successfully enriched by the use of interleukin-2 (IL-2) prepared from human tonsils and spleens. That is, peripheral blood lymphocytes cultured for 3 or 4 weeks with IL-2 strongly inhibited the patient's own lymphocyte-proliferative responses to alloantigen or phytohemagglutinin (PHA). Quantitative fluorescence measurement for immunologic analysis of phenotypic characterization of the cells was made on FACS-IV with monoclonal antibodies anti-Leu-1 anti-Leu-2a, anti-Leu-3a, anti-Leu-4, anti Leu-5, anti-Leu-7, and anti-HLA-DR and goat anti-human immunoglobulin (Ig). Functional suppressor T-cells expanded with IL-2 showed the following phenotype: Leu-1+ Leu-2a+, Leu-3a-, Leu-4+, Leu-5+, Leu-7-, HLA-DR+, human Ig-. The IL-2-dependent suppressor T-cells could be obtained only when the cells were derived from patients with systemic metastasis of gastric carcinoma. These findings suggest that generation of IL-2-dependent suppressor T-cells is the result of large tumor burdens; this may exert negative cellular control in the immune responses, thus inducing the status of the lower cell-mediated antitumor immunity, and may promote cancer progression in gastric cancer patients.
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