EFFICIENT EXPANSION OF TUMOR-INFILTRATING LYMPHOCYTES FROM SOLID TUMORS BY STIMULATION WITH COMBINED CD3 AND CD28 MONOCLONAL-ANTIBODIES

Combined CD3 and CD28 monoclonal antibodies (mAb) may initiate efficie nt activation and expansion of tumor-infiltrating lymphocytes (TIL). I n this study we compared phenotypical and functional characteristics o f TIL from a group of 17 solid human tumors, stimulated either by high -dose recombinant interleukin 2 (rIL-2, 1000 IU/ml) or by a combinatio n of anti-CD3 and anti-CD28 monoclonal antibodies in the presence of l ow-dose rIL-2 (10 IU/ml). Compared to activation with high-dose rIL-2, stimulation of TIL with CD3/CD28 mAb induced significantly stronger p roliferation and yielded higher levels of cell recovery on day 14. Fol lowing the CD3/CD28 protocol, expansion of an almost pure population o f CD3+ cells was obtained. Whereas CD4+ cells dominated in the first w eek of culturing, within 4 weeks the CD8+ population increased to over 90%. The specific capacity to kill autologous tumor cells was not inc reased as compared to the high-dose rIL-2 protocol, but all cultures s howed high cytotoxic T cell activity as measured in a CD3-mAb-mediated redirected kill assay. These studies show that combined CD3 and CD28 mAb are superior to rIL-2 with respect to the initiation of expansion of CD8+ cytolytic TIL from solid tumors. Stimulation with specific tum or antigens at a later stage of culturing may further augment the expa nsion of tumor-specific cytolytic T cells.