Intradermal Recombinant Interleukin 2 Enhances Peripheral Blood T-Cell Responses to Mitogen and Antigens in Patients with Lepromatous Leprosy

Thirty-one patients with lepromatous leprosy received recombinant interleukin 2 (IL-2) intradermally in doses ranging from 10 to 30 micrograms. Before injection and at time intervals of 2-21 days thereafter, samples of peripheral blood mononuclear cells (PBMC) were obtained. Single or multiple injections (1-3) of IL-2 did not modify the total number of circulating lymphocytes or the number of T cells and the CD4/CD8 T-cell ratio. However, IL-2 had a pronounced influence on the [3H]thymidine incorporation in response to various stimuli 4-8 days after intradermal IL-2. Stimulation indices of three- to sevenfold above pre-IL-2 levels were observed with the polyclonal activator phytohaemagglutinin (PHA) and enhanced thymidine incorporation occurred in the presence of antigens to which the patients were already sensitized, such as purified protein derivative and BCG. IL-2 had no effect on the unresponsive state of lepromatous leprosy patient T cells to the antigens of Mycobacterium leprae.