T lymphocyte subpopulations in leprosy patients and their relation with circulating immune complexes.

The possible relationship between circulating immune complexes (CIC) and peripheral T lymphocyte populations was studied in thirteen active multibacillary leprosy (10 lepromatous--LL--and 3 borderline lepromatous--BL--) and 19 matched controls. Theophylline-resistant T cells (The-R, a lymphocyte subpopulation displaying helper activity on B cells) and total T cells were assessed by means of the E rosette technique, with and without previous theophylline incubation, 1h 37 degrees C, respectively. CIC were quantified by 125I-C1q binding test. Although leprosy patients showed a statistical non significant light depression in total T cells the remarkable variability in circulating levels of The-R T cells enabled us to separate them into two well delineated groups (in relation to this variable p less than 0.001) with no difference in age, sex and bacteriologic state: a) leprosy patients with The-R T cells proportionally conserved (6LL and 2BL); b) leprosy patients with The-R T cells proportionally depressed (4LL and 1BL). Patients belonging to the latter group showed the highest statistically significant levels of CIC. Even though we do not discard an unknown factor being responsible for our findings, we believe that this inverse relationship between elevated CIC and depressed The-R circulating T cells might be representing a lower helper activity on antibody synthesis intending to reduce its excessive production.

Correlation between macrophage activation and bactericidal function and Mycobacterium leprae antigen presentation in macrophages of leprosy patients and normal individuals.

The killing of Mycobacterium leprae by resting and gamma interferon (IFN-gamma)-activated macrophages in normal subjects and leprosy patients was assessed. Resting macrophages from normal individuals demonstrated the ability to kill M. leprae. For macrophages from tuberculoid patients, killing of M. leprae was only achieved in the presence of IFN-gamma, suggesting that initial T-cell activation occurs prior to the killing of M. leprae. In contrast, though activation with IFN-gamma rendered the lepromatous macrophages microbicidal, it failed to induce lymphocyte proliferation, suggesting a defect at either the antigen-presenting cell or the lymphocyte level or both. The concept that T-cell anergy is primarily due to lack of lymphokine generation was ruled out by our results, since responsiveness was restored in only a small proportion of lepromatous patients after exogenous lymphokine addition. In conclusion, this study demonstrated that killing and antigen presentation are two independent events. It appears that the ability of the macrophages per se to kill M. leprae may be of greater importance than lymphocyte-mediated activation for protection against M. leprae infection.

Correlation of in vitro Fc receptor assay with in vivo mouse foot pad method.

Resistant strains of M. leprae have been reported to the various antileprosy drugs. There is currently no accepted test to identify the susceptibility pattern of M. leprae to the drugs in a short period. The only accepted test is the mouse foot method which takes a long period to yield results. The Fc receptor assay using the ability of viable M. leprae to alter the membrane of the macrophage is well established. It takes only ten days and is inexpensive. In 6 cases of leprosy patients the susceptibility pattern was worked out both with the in vitro Fc receptor assay and the vivo in mouse foot method The results correlated very well leading to the fact that the assay system is reliable. Hence it can be used not only to study the status of a patient, but also to shortlist the number of compounds to be tested on the mouse foot pad as anti-leprosy drug candidates.

Lepromin-induced lymphoproliferative response of experimental leprosy monkeys: regulatory role of monocyte and lymphocyte subsets.

We investigated the immunological status of seven normal, control Mangabey monkeys and 23 Mangabey monkeys experimentally inoculated with Mangabey-origin Mycobacterium leprae. Clinically, these monkeys were divided into three broad groups: a recently inoculated group, a resistant group, and a susceptible group. The resistant group included 11 monkeys, seven of which showed no clinical sign of disease to date and four of which had shown local disease that partially regressed spontaneously. The susceptible group included eight monkeys, five of which have disseminated disease and three with local but stable disease. When peripheral blood mononuclear cells of these monkeys were cultured with Dharmendra-type human lepromin, one of seven normal monkeys, four of four of the recently inoculated group, seven of 10 resistant monkeys, and three of eight susceptible monkeys showed significant responses. In this experimental monkey model, we studied possible regulatory mechanisms by using OKT4- and OKT8-enriched lymphocytes, and Fc receptor-positive (FcR+) and FcR- monocyte (M phi) subsets. The OKT4+ subset was the main lepromin-responsive cell type. High percentages of OKT8+ cells showed a good negative correlation with the lymphoproliferative responses of T-enriched cells supplemented with unfractionated M phi. But the depletion of OKT8+ cells could not increase the response of nonresponding monkeys' lymphocytes. The resistant group and susceptible group did not differ in their percentages of OKT8+ cells. Because OKT8+ cells negatively regulate the response of lymphocytes and OKT4+ cells are the main responding cells, OKT8+ cells are phenotypically and functionally suppressor cells and OKT4+ cells are the helper/inducer cell population in this system. The FcR- M phi population mainly includes antigen-presenting activity, but high percentages of FcR- M phi showed a significant negative correlation with lymphoproliferative responses in the resistant group. A weak but significant lymphocyte response to Dharmendra lepromin was obtained by depleting FcR+ M phi from cultures of some susceptible monkeys, whereas lymphocytes of other susceptible monkeys remained unresponsive to lepromin. By these criteria, we could find an array of immunological defects in monkeys with experimental leprosy. The data suggest that some immunological defects may exist in the OKT4+ lymphocytes or FcR- M phi of leprosy monkeys.