The selective expansion of functional T cell subsets

Adoptive cellular immunotherapy is considered a potential treatment for a wide range of diseases, including cancer, infectious diseases, and autoimmune disorders. We have developed a method using a conditioned medium, XLCM, that selectively expands several different T cell subsets with a view to their use in cell therapy. Primary FBS-free suspension cultures of human peripheral blood low-density mononuclear cells treated with XLCM reproducibly expand over 100,000-fold within a period of 4 weeks. CD4+ T cells and CD8+ T cells expand sequentially in the unfractionated cultures, and relatively pure populations of CD4+ and CD8+ T cells may be expanded from populations first enriched in the respective T cell subset. CD4+ T cells cultured in XLCM produce cytokines consistent with the expansion of Th1, Th2, and Th0 subsets, whereas CD8+ T cells cultured in XLCM are cytolytically competent. An interesting feature of T cells cultured in XLCM is the persistence of 5%-10% CD4+CD8+ double-positive T cells in spite of substantial single-positive T cell expansion, suggesting that these cells also proliferate in XLCM. In addition to subsets of TCRalphabeta+ T cells, TCRgammadelta+ T cells are also significantly expanded by XLCM. These results demonstrate that XLCM efficiently expands several functional T cell subsets and provides a means of obtaining selected populations suitable for use in cellular immunotherapy.