Superantigen-induced human CD4+ helper/killer T cell phenomenon. Selective induction of Th1 helper/killer T cells and application to tumor immunotherapy.

Human CD4+ T cells activated with staphylococcal enterotoxin A (SEA) were fractionated by Percoll discontinuous density gradient centrifugation to enrich SEA-reactive CD4+ T cells. The SEA-reactive CD4+ T cells showed significant cytotoxicity, so-called superantigen-dependent cell-mediated cytotoxicity, against SEA-coated class II-positive tumor cells. During lysis of SEA-coated tumor cells, SEA-reactive CD4+ T cells produced high levels of IL-2 and IFN-gamma but not IL-4 in an Ag-specific manner. The skewing of human CD4+ T cells to Th1-type helper/killer T cells was also demonstrated when SEA-reactive CD4+V beta 5.3+ clonal T cells were cultured with SEA, but not with PHA or OKT3 mAb. Interestingly, the generation of SEA-reactive helper/killer T cells was negatively regulated by IL-4, but up-regulated by IL-12. The SEA-reactive CD4+ helper/killer T cells were able to generate from PBMC of tumor patients and could be expanded to 10(9) levels in a 7-day culture. The SEA-reactive CD4+ helper/killer T cells were specifically targeted to c-erbB-2 positive human colon cancer cells using SEA-conjugated-anti-c-erbB-2 mAb. These results initially demonstrated that SEA-activated human CD4+ T cells are a Th1 type of Th cell that has both helper and killer functions which may be useful for adoptive tumor immunotherapy in combination with SEA-conjugated antitumor mAb.