in vitro immunization of patient T cells with autologous bone marrow antigen presenting cells pulsed with tumor lysates

Abstract

Presentation of cell-associated antigen to T cells is a critical event in the initiation of an anti-tumor immune response but it appears to often be deficient or limiting. Here we report an experimental system for stimulation of human T lymphocytes using autologous antigen presenting cells (APCs) and autologous tumor cells. Two types of APCs were prepared from human bone marrow: MC and DC. MC were produced by using GM-CSF and SCF. DC were obtained with the same cytokines plus IL-4. DC and MC were generated in parallel from the same patients and their phenotypes and capacities to prime T lymphocytes were analyzed and compared. MC were CD14+, CD1a-, CD33+ and HLA-DR+. Two populations of DC were defined: immature DC were uniformly CD1a-; mature DC expressed CD1a, CD80, CD86, HLA-DR, CD54 and CD58 but lacked surface CD14. Stimulation of autologous T lymphocytes was studied by measuring their proliferation and cytotoxic function. In more than 80% of our experiments the proliferation of autologous T lymphocytes cocultured with APC pulsed or not with tumor cell lysates was higher than that of T cells cultured alone. DC were more effective than MC in stimulating proliferation of lymphocytes. The capacity of a patient's autologous bone marrow-derived APC to stimulate T cells when exposed to autologous tumor cell lysates suggest that such antigen-exposed APC may be useful in specific anti-tumor immunotherapy protocols.