Recombinant interleukin-2 in lepromatous leprosy lesions: immunological and microbiological consequences.

Seven patients with lepromatous leprosy (LL) were inoculated with recombinant interleukin-2 (rIL-2) at 5 lesional sites on the back, four sites receiving one dose of 10 micrograms and biopsy specimens being obtained on 4 consecutive days after the injection. At the 5th site, rIL-2 was instead administered over several days, three patients receiving a total dose of 40 micrograms and 4 patients 150 micrograms, while biopsy specimens from this site were obtained 7, 14 and 21 days after the first injection. Most injection sites developed features of a delayed-type hypersensitivity reaction, namely erythema and induration at the injection site, infiltrates rich in T helper cells, monocytes, and Langerhans cells, and at sites receiving higher doses, multinucleated Langhans giant cells and epithelioid granulomas. In some patients, there were favourable shifts in histological classification or small changes in bacterial load. Low doses of rIL-2 injected into LL lesions rapidly enhance cellular immunity and may alter the histological classification or bacterial load at the injection site.