Autolymphocyte therapy. II. Dependence of in vivo anti-tumor specificity and long-term immunity against murine melanoma and carcinoma on ex vivo activated donor memory T-cells.

Autolymphocyte therapy (ALT) is tumor-specific adoptive cellular therapy of neoplastic disease in human tumor-bearing hosts based upon nonspecific ex vivo activation of autologous peripheral blood lymphocytes. We have previously demonstrated that nonspecific ex vivo activation of splenocytes from murine tumor-bearing hosts using a mixed-lymphocyte culture supernatant without tumor antigen results in the expansion of the CD44+ (memory) T-cell subset and that depletion of these CD44+ T-cells results in the abrogation of all in vivo anti-tumor effects. To examine other means of generating anti-tumor-specific effectors, splenocytes of C57BL/6J healthy syngeneic mice and mice with B16 melanoma (B16 mice) or Lewis lung (3LL) carcinoma (3LL mice) were activated ex vivo using low doses of the mitogenic monoclonal antibody OKT3 and a mixture of previously prepared autologous cytokines (T3CS). Immunophenotypic studies of splenocytes pre- and postactivation by T3CS revealed preferential expansion of Thy-1.2+CD44+ (memory) T-cells. 3LL and B16 mice received ALT cells derived from splenocytes of 3LL mice, B16 mice, or healthy mice; fresh splenocytes from 3LL or B16 mice; or CD44-depleted ALT cells derived from splenocytes of 3LL or B16 mice. Significant anti-tumor activity as shown by a reduction in primary tumor size, decreased mean number of lung metastases (Day 21), and prolonged survival was demonstrated in 3LL mice that received 3LL-derived ALT cells and in B16 mice that received B16-derived ALT cells. To test long-term immunity, adoptive transfer of subtherapeutic numbers of ex vivo activated Thy-1.2+ memory T-cells were infused into healthy congenic B6.PL Thy-1a/CY (Thy-1.1+) mice. On rechallenge with 3LL or B16 tumor, long-term tumor-specific immunity was shown to be dependent on donor Thy-1.2+ memory T-cells. These data demonstrate that tumor-specific adoptive cellular therapy and long-term tumor immunity is possible using splenocytes from tumor-bearing mice that are activated ex vivo by T3CS and is dependent on the infusion of memory T-cells. These data are consistent with clinical results in patients with metastatic melanoma and renal cell carcinoma treated with T3CS-activated lymphocytes.