Immunosuppressive factor from the spleen in gastric cancer patients.

The spleens of gastric cancer patients were examined to determine whether this organ releases an immunosuppressive factor. Compared to serum from peripheral blood, serum from splenic venous blood of advanced gastric cancer patients had greater suppressive activity to normal lymphocyte responses to phytohemagglutinin (PHA); it also contained significantly more immune complexes. Furthermore, the supernatant from spleen cell cultures from advanced gastric cancer patients significantly suppressed normal lymphocyte responses to PHA. This immunosuppressive activity was enhanced when the supernatant was from cultures of separated nonadherent subpopulations. These observations were not detected in patients with early gastric cancer. The blastogenic response to PHA and the percentage of T-cells among spleen cells was not affected by the cancer stage. These results suggest that the spleen of patients with advanced gastric cancer participates in the induction of serum immunosuppressive factors, possibly due to a change in splenic lymphocyte subsets.