Loss of Interleukin - 2 Requirement for the Generation of T Colonies Defines an

Accessory cells and/or soluble factors, together with interleukin 2 (lL2). are required for the proliferation and differentiation of phytohemagglutinin (PHA)-activated T lymphocytes. Human T-lymphotropic virus. type I (HTLV-l). a human retrovirus isolated from patients with adult T cell leukemia. can transform T cells in vitro. We investigated the role of HTLV-l-transformed T cell lines as accessory cells in promoting the growth of T colony-forming cells. We found that T cells isolated by E rosetting and then activated with PHA, when seeded with as few as 5 x 1 O irradiated HTLV-l-producing cells. could generate colonies in the absence of 112. We analyzed further the effects of HTLv-I virions on T colony formation. Infection of T cells with semipurified HTLV-l viral particles promoted colony formation. in the absence of lL2, of accessory cells or soluble factors. The same results were obtained either