Reduced suppressor cell response to Mycobacterium leprae in lepromatous leprosy.

We have previously shown that concanavalin A (ConA) induction of suppressor cell activity is impaired in patients with lepromatous leprosy (LL). In this study, we demonstrated that the proportion of cells bearing the Leu8 antigen (associated with suppressor-inducer cells) is low in LL patients and tends to normalize during the erythema nodosum leprosum (ENL) episode. Antigen-induced suppressor cell function was evaluated by a two-stage assay. In the first stage, peripheral blood mononuclear cells (PBMC) were cultured for 5 days either in the presence of gamma-irradiated Mycobacterium leprae or in tissue culture medium as a control. In the second stage, mitomycin C-treated suppressor or control cells were added to phytohemagglutinin (PHA)- or ConA-stimulated autologous PBMC. The results indicate that the ability of M. leprae to induce suppressor activity was lower in LL patients than in patients with tuberculoid (TT) and intermediate clinical (BB, BL, BT) forms and Mycobacterium bovis BCG-immunized normal controls. In ENL patients, the percent suppression was between that of TT and normal individuals. M. leprae-induced suppression was more effective on ConA- than on PHA-triggered T-cell proliferation in all groups. In contrast, normal PBMC cultured for 5 days in RPMI 1640 medium (N-C) and cells from patients with leprosy (TT-C and LL-C) had effects of their own on PHA- or ConA-induced proliferation. LL-C depressed the response to ConA and enhanced PHA-induced proliferation of autologous cells. Conversely, TT-C reduced PHA-induced proliferation and increased the ConA response. Suppression of proliferation could not be overcome with exogenous interleukin-2 and was not related to the induction of the Tac antigen. The abilities of LL, TT, ENL, and normal cells to proliferate upon PHA or ConA stimulus were similar, indicating that the defect in the generation of in vitro suppression by M. leprae in LL patients occurred during the induction period (step 1 of assay).     

Studies on T cell subsets and functions in leprosy.

T cell subsets and T cell functions were explored in 31 leprosy patients with the following methods: determination of the percentages of the different T cell subpopulations defined by monoclonal antibodies directed at total T cells, helper T cells and suppressor/cytotoxic T cells; measurement of the in vitro proliferative responses to mitogens; study of the concanavalin A-induced suppressive activity, assessed on MLC; measurement of delayed-type hypersensitivity by skin testing. The confrontation between immunological lepromatous patients without type-2 reaction (erythema nodosum leprosum), (2) lepromatous patients without ENL (erythema nodosum leprosum), (2) lepromatous patients was recent ENL and (3) tuberculoid patients. Unexpectedly, groups 1 and 3, although differing strongly in their clinical status and their sensitivity to lepromin (absent in group 1 and strong in group 3), showed a similar immunological profile with a normal percentage of T cells and a normal distribution of T cells among the major T cell subset contrasting with a moderate decrease of proliferative responses to mitogens and impaired delayed-type hypersensitivity reactions. Concanavalin A-induced suppressive activity was type-2 reaction) strongly differed from both other groups, showing striking abnormalities other groups, showing striking abnormalities of the repartition of the T cell subsets, with increased percentages of helper T cells and decreased percentages of suppressor T cells, and elevated proliferative responses to mitogens. Concanavalin A-induced suppressive activity was reduced in most patients of this group. It is suggested that this imbalance between T cell subsets contributes to the occurrence of ENL reactions in lepromatous patients.     

Natural emergence of antigen-reactive T cells in lepromatous leprosy patients during erythema nodosum leprosum.

Fifteen lepromatous leprosy (LL) patients undergoing erythema nodosum leprosum (ENL) reactions were compared with 13 stable, uncomplicated, anergic individuals of the same leprosy background. ENL patients showed significant antigen-induced leukocyte migration inhibition (migration index = 0.058 +/- 0.01), paralleling the values obtained with a responder tuberculoid leprosy population (migration index = 0.04 +/- 0.004). Both phytohemagglutinin-induced general T-cell proliferation and, more significantly, antigen-induced lymphoproliferation were enhanced during the acute phase of the reaction. Suppressor cell activity, monitored by a costimulant assay, showed enhanced antigen-stimulated suppression of mitogen responses. Interestingly, the improvement in in vitro T-cell responses was not reflected in dermal reactivity, since 48-h delayed-type hypersensitivity responses after intradermal injection of soluble Mycobacterium leprae antigens continued to be poor. After subsidence of reactional lesions, leukocyte migration inhibition, lymphoproliferation, and suppressor cell activity were reduced to the unresponsive state seen in stable LL patients. Significantly, perturbations of T-cell reactivity are detectable in ENL reactions, indicating the natural but transient emergence of antigen-induced T cells in LL.     

Defect in the generation of cytotoxic T cells in lepromatous leprosy.

Cytotoxic T cells are consistently produced in normal individuals after in vitro stimulation by a pool of mitomycin-treated normal lymphocytes. Patients suffering from lepromatous leprosy (LL), presenting with large amounts of Mycobacterium leprae and without a history of erythema nodosum leprosum (ENL) are unable to generate such cytotoxic T cells, while lepromatous patients with ENL which, in the present study were all deprived of M. leprae, react normally.     

Differences in predominant T cell phenotypes and distribution pattern in reactional lesions of tuberculoid and lepromatous leprosy.

The nature and histological pattern of the cutaneous infiltrates of 17 leprosy patients in reversal reactions (Type I) and erythema nodosum leprosum (Type II, ENL) were compared with tissues from 18 non-reactional borderline leprosy (BT, BL) and lepromatous leprosy (LL) patients using monoclonal antibodies and immunofluorescence. Reactional BT lesions showed a mild increase in OKT11+ pan T cells as compared to non-reactional tissues and a significant influx of OKT8+ (suppressor/cytotoxic) cells which were peripherally localized in the lymphocyte mantle surrounding the epithelioid cells. The Leu 3a+ (helper/inducer) cells were scattered amongst the lymphocytes and macrophages. The mean ratio (+/- s.d.) of Leu 3a+/OKT8+ cells was 1.88 +/- 0.64 in Type I BT reactions as compared to 2.95 +/- 0.95 in BT lesions. In contrast, lesions of BL reversal reactions and ENL showed a more marked increase in pan T cells with a preponderance of the helper/inducer subset, Leu 3a+/OKT8+ ratio being 2.26 +/- 0.61 and 0.93 +/- 0.57 in BL reactional and non-reactional lesions, respectively. Interestingly, this increase in the numbers of the T cells reached levels observed in BT lesions. The distribution pattern of OKT8+ cells was similar to Leu 3a+, both being diffusely scattered amongst the bacilli laden macrophages. Ia like antigens were present in all granulomas and were abundant on lymphocytes and macrophages and less conspicuous on epithelioid cells. T6+ Langerhans cells were uniformly increased in all reactional lesions. It would appear that the changes observed in both Type I and Type II reactions are similar in the lepromatous group of patients. They differ significantly from the BT reversal reaction in terms of the dominant T cell subset and the microanatomical distribution of the OKT8+ cells in the lesions.     

Effect of oral colchicine on T cell subsets, monocytes and concanavalin A-induced suppressor cell function in asthmatic patients

Asthmatic patients have a deficiency of concanavalin A-(Con A) induced suppressor cell function. We tested whether oral colchicine 0·5 mg twice daily for 7 days could correct this immunoregulatory abnormality. Peripheral blood mononuclear cells were incubated with Con A and then suppression of proliferation was measured by co-culture of these cells with healthy volunteers’mononuclear cells and phytohaemagglutinin. Sixteen asthmatic patients had significantly (P < 0·002) decreased Con A-induced suppressor cell function (17·0±17·2%, mean ± s.d.) as compared to 13 healthy volunteers (37·9±14·9%). Oral colchicine significantly (P < 0·05) increased, though only partially corrected, these 16 asthmatic patients’Con A-induced suppressor cell function (28·1±14·3%). Asthmatic patients had an increased number of monocytes (691±289 vs 388±271/mm³ for normals, P < 0·01) and a normal number of lymphocytes, Leu 4+ total T cells, Leu 3+ helper/inducer T cells, and Leu 2+ suppressor/cytotoxic T cells as well as a normal Leu 3/Leu 2 ratio. Oral colchicine significantly (P < 0·005) decreased the number of monocytes (451±255/mm³) without significantly affecting the number of lymphocytes, Leu 4+, Leu 3+, or Leu 2+ T cells, or the Leu 3/Leu 2 ratio. These results are consistent with the hypothesis that the deficiency of Con A-induced suppressor cell function in asthmatic patients may be due, in part, to an increased number and/or abnormal activity of monocytes. If so, then oral colchicine may have partially corrected the deficiency of Con A-induced suppressor cell function by decreasing the number and/or modulating the activity of monocytes.     

Production of transforming growth factor-beta 1 (TGF-beta1) by blood monocytes from patients with different clinical forms of leprosy

In the present study, the concentration of TGF-beta1 secreted by adherent cells isolated from human peripheral blood mononuclear cells (PBMC) and either stimulated with PGL-1 or lipopolysaccharide (LPS) or left unstimulated was determined by ELISA. The cells were isolated from untreated patients with different clinical forms of leprosy and healthy individuals. The adherent cells exhibited spontaneous release of TGF-beta1 in all clinical forms of leprosy and in healthy individuals; however, lepromatous leprosy/borderline leprosy (LL/BL) patients presenting erythema nodosum leprosum (ENL) displayed significantly higher concentrations of TGF-beta1 than either the other patients studied or the controls. These high TGF-beta1 levels were consistently observed when LL/BL ENL cells were stimulated with phenolic glycolipid (PGL-1) or LPS, and even in the absence of a stimulus (P < 0.01). The most significant differences in TGF-beta1 levels were observed when comparing the results in the presence of PGL-1 from ENL with, in order of significance: tuberculoid leprosy (TT) patients (P < 0.001), LL/BL patients without ENL (P < 0.01), healthy individuals (P < 0.01) and borderline-borderline/borderline-tuberculoid (BB/BT) patients with reversal reaction (RR) (P < 0.01). The BB/BT patients produced equivalent levels of TGF-beta1 compared with LL/BL patients without ENL, for all types of stimuli (P > 0.05). In contrast, TT patients produced the lowest levels of TGF-beta1 among all the subjects studied (both patients and healthy controls), especially following PGL-1 stimulation (P < 0.001, and P < 0.05, respectively). In conjunction with our previous data regarding TGF-beta1 expression in dermal lesions, it appears that TGF-beta1 probably plays different roles in leprosy: (i) to mediate a suppressive action locally, associated with the presence of PGL-1, and (ii) to induce proinflammatory effects when secreted systemically by monocytes, thereby acting as a modulatory cytokine in the acute inflammatory reactions of ENL and associated with the Th2 immune response in multibacillary forms of leprosy.     

Autoantibodies in lepromatous leprosy

Lepromatous leprosy patients often develop erythema nodusum leprosum (ENL) reactions mainly during treatment of the disease. Hence, this study sought to investigate correlation between the prevalence of certain autoantibodies and ENL reactions in these patients. The patients included in the study were fifty patients with lepromatous leprosy and a similar number of normal controls. Sera were collected from the patients and normal controls and the prevalence of circulating rheumatoid factor antinuclear and antismooth muscle antibodies was determined. The prevalence of autoantibodies was increased in lepromatous leprosy as compared with normal controls. The prevalence of these autoantibodies were affected differently by the ENL reactions. ENL lepromatous leprosy showed a slight decrease in prevalence of antinuclear and antismooth muscle antibodies, whereas there was a slight increase in the prevalence of rheumatoid factor in ENL lepromatous leprosy. The levels of serum immunoglobulins tended to show a decline towards ENL lepromatous patients compared with the uncomplicated lepromatous patients. The significance of these finding is discussed in relation to their possible role in the pathogenesis of ENL reaction. It is concluded that some of these autoantibodies and immunoglobulins may be utilized during ENL reactions in the formation of immune complexes.     

Association of C4B deficiency (C4B*Q0) with erythema nodosum in leprosy

A considerable number of studies have postulated significant associations between susceptibility to the different clinical manifestations of leprosy and the MHC, In this investigation, the association between the MHC class III complement proieins C2, BF, C4A and C4B and leprosy in a patient population of Southern Brazil was studied. A total of 109 non-related leprosy patients was investigated; 73 presented wilh lepromatous leprosy (LL), 46 of Ihem had the immunopathological reaction of erythema nodosum (ENL), the remaining 36 were tuberculoid, borderline and indeterminate leprosy (TIBL) patients. The control group included 172 healthy individuals matched with the patients according lo their ethnic and geographical origin, C2, BF, C4A and C4B allotypes were determined by slandard technologies including Western blots for C2 and C4 variant alleles wilh monoclonal and polyclonal antibodies. Non-expressed (‘silent’) C4 alleles in hemizygously deficient individuals were estimated semiquantitatively on the basis of the C4A and C4B isolype ratio and by the M ASC (‘minimal chi-square’) method. The results showed a significantly elevated presence of the non-expressed C4B allele (C4B*Q0) in the LL and ENL patient groups in comparison with the controls. The most signifieant difference was observed in the ENL group when compared with the controls. In addition, all patients who were homozygously C4B-deficient had ENL, and most of them had the BF*F1 allele. The comparison between LL patients with and without ENL also showed a statistically significant difference in the presence of C4B*Q0, indieating thai C4B deficiency itself is associated with EN L. The relative risk of LL patients with the C4B*Q0 allele suffering from ENL was 53 compared with LL palients without C4B*Q0, Since immune complexes (IC) are considered to be the palhogenic cause of ENL, our findings indicate thai C4B deficieney may play an important role in the abnormal immune response against Myeobaeterium leprae and in the lack of IC clearance, leading to ENL reactions. Individuals wilh this allele seem to be at a higher risk of developing pathologieal immune reactivity in lepromatous leprosy.     

Polymorphonuclear cell function in the various polar types of leprosy and erythema nodosum leprosum.

Polymorphonuclear leukocyte motility, both in vivo and in vitro, and reduction of Nitro Blue Tetrazolium was studied in tuberculoid and lepromatous leprosy patients and a group of lepromatous patients with erythema nodosum leprosum (ENL). A profound defect in random migration, chemotaxis, and chemokinesis was found in lepromatous patients with and without complicating ENL, and marked depletion of skin window migration confirmed these in vitro findings. Tuberculoid patients exhibited a mild defect in polymorphonuclear leukocyte motility. Serum inhibitors of normal polymorphonuclear leukocyte chemotaxis were found in all types of leprosy, but sera from lepromatous and ENL patients were most inhibitory. Resting levels of Nitro Blue Tetrazolium reduction were normal in all three groups. Reconstitution of polymorphonuclear leukocyte cells from normal and ENL patients with ENL serum, however, showed increased Nitro Blue Tetrazolium reduction well above the normal range, whereas reconstitution with normal, lepromatous, and tuberculoid sera failed to increase Nitro Blue Tetrazolium reduction above the normal values.     

Suppressor cell activity and phenotypes in the blood or tissues of patients with leprosy.

Suppressor cell activity has been demonstrated in the peripheral blood of patients with leprosy. Cells bearing the suppressor/cytotoxic phenotype have been enumerated in both peripheral blood and tissues, and microanatomical differences in tissue distribution have been observed. This first generation of studies has been characterized by considerable disagreement, a not unusual circumstance in the study of leprosy. In the case of blood suppressor cell activity, there appears to be no doubt as to its existence, but much uncertainty regarding its distribution. Concerning peripheral blood phenotypic suppressor cells, the observed differences in lepromatous and ENL patients may well reflect differences in methods used. Concerning phenotypic suppressor cells in tissue, there is no agreement as to their numbers or microanatomical distribution across the spectrum of leprosy or in its reaction states. Although these observational differences make firm conclusions impossible, this first generation of studies has provided new ways of considering old problems. For example, lepromin unresponsiveness might be a consequence of active cellular suppression. Differences in the numbers (or percentages) of the suppressor phenotype in blood or tissues of lepromatous patients with or without ENL reopens the door to the possibility of cell-mediated immune mechanisms in the pathogenesis of ENL. The identification of defective suppressor cells as important in the pathogenesis of hypergammaglobulinaemia is of interest in and of itself, but also gives rise to the possibility that other kinds of phenomena may be a consequence of defective or effete suppressor mechanisms. The observation of microanatomical differences in the distribution of the suppressor phenotype in tuberculoid and lepromatous leprosy indicates that effective or ineffective immunity might be a sequela of particular interactions between the suppressor/cytotoxic and helper/inducer phenotypes, and that these interactions merit further study. These new perspectives may be subject to experimental testing by the next generation of studies, which will surely include the techniques of clonal expansion and limiting dilution, as well as the study of interleukins 1 and 2.     

Circulating T-cell numbers and their mitogenic potential in leprosy--correlation with mycobacterial load.

The effect of treatment and mycobacterial load on circulating T-cell numbers and their functional ability was investigated in forty-one patients with leprosy. Both early binding T cells and their responses to phytohaemagglutinin (PHA), concanavalin A (Con A) and pokeweed mitogen (PWM) were profoundly and uniformly depressed in untreated, and partially treated, bacilleferous lepromatous leprosy (LL) patients as compared with normal subjects and tuberculoid patients. On elimination of mycobacteria, subsequent to chemotherapy, LL patients regain normality in T-cell numbers and their functions. On the other hand, the specific response of lymphocytes to M. leprae did not alter with decrease in mycobacterial load. It appears that the decrease in T-cell numbers and the deficit in their mitogenic potential is a secondary consequence of disease and is related to the antigenic load in patients with lepromatous leprosy.     

Inhibition of interleukin-2 production by adherent cell factors from lepromatous leprosy patients.

Twenty-four hour supernatants (MoF) were obtained from monocyte rich 2 h adherent cells of 19 leprosy patients and four healthy contacts. MoF from borderline and lepromatous patients produced 52-61% inhibition of human interleukin-2 (IL-2) production by a PHA conditioned T cell line (Jurkat). Non-adherent cell supernatants and MoF from tuberculoid and healthy individuals had little effect on IL-2 production. The suppression effected by MoF was in the first 12 h of initiation of PHA stimulated Jurkat cell cultures. Suppressive MoF did not interfere with (1) IL-2 release, (2) IL-2 utilization by Con A-induced T cell blasts or (3) constitutive proliferation of Jurkat cells. Such MoF were released spontaneously from adherent cells of bacilliferous leprosy patients but required in vitro antigen triggering in long term treated lepromatous patients. It is possible that the unresponsiveness associated with lepromatous leprosy is related to the inhibition of IL-2 production by suppressive factors, thereby, preventing the further expansion of antigen reactive T cells.     

In situ characterization of T lymphocyte subsets in the reactional states of leprosy.

Using monoclonal antibodies and the immunoperoxidase technique, the numbers and distribution of T lymphocyte subsets in the tissues of reactional states of leprosy (six reversal reaction, nine erythema nodosum leprosum (ENL) and two Lucio's reaction) were determined and compared with those found in stable, non-reactional patients (six tuberculoid, two borderline lepromatous and seven lepromatous). The pattern of segregation of the suppressor/cytotoxic phenotype at the periphery of the granuloma was found in both non-reactional tuberculoid lesions and reversal reactions, but was better developed in the former. In ENL and Lucio's reaction, as well as in non-reactional lepromatous tissue, the helper/inducer and suppressor/cytotoxic phenotypes were both admixed with the aggregated histiocytes. However, the helper/suppressor ratio in ENL (2.1 +/- 0.4) was significantly larger than that in non-reactional lepromatous tissue (0.7 +/- 0.4, P less than 0.001). The immature thymocyte antigen OKT6 was found on scattered large non-lymphoid cells, most commonly in tuberculoid and reversal reaction tissues, less commonly in ENL, but only irregularly in non-reactional lepromatous tissue. The peripheral pattern of the suppressor/cytotoxic phenotype may be an immunohistological reflection of a cell-mediated immune response common to both non-reactional tuberculoid and reversal reaction patients. The reversal of the helper/suppressor ratio in ENL as compared to non-reactional lepromatous disease suggests some role for cell-mediated immunity in the pathogenesis of ENL. The OKT6 positive cell is of unknown origin and function.     

The effect of delayed addition of antigen and 'E' rosetting on the proliferative response to mycobacterial antigens of peripheral blood lymphocytes from normal individuals or from patients with tuberculosis or leprosy.

Some suppressor cells are reported to lose their activity when precultured without stimulus in vitro. We have investigated the role of such suppressors in responsiveness to mycobacterial antigens of peripheral blood mononuclear cells (PBMNC) from patients with leprosy or tuberculosis, or from normal donors. Delayed addition of mycobacterial antigens (Mycobacterium leprae, Mycobacterium vaccae and Mycobacterium tuberculosis), but not of a fungal antigen (Candida albicans) caused enhanced responses using PBMNC from most normal donors, or tuberculoid leprosy (TT/BT) patients. However, the effect was less common using PBMNC from the lepromatous leprosy (BL/LL) group. (P less than 01.01, using M. leprae, relative to the TT/BT group), suggesting that this type of suppression reflects a normal mechanism, which is diminished rather than increased in anergic patients. Delayed addition of antigens to 'E'-rosetting cells did not result in enhanced responses. However, the different effects of 'E'-rosetting on the responses to the mycobacterial antigens of cells from normals, TT/BT and BL/LL patients, suggested that there may be two types of proliferative response to these antigens.     

Suppressed natural killer cell activity during episodes of erythema nodosum leprosum in lepromatous leprosy.

Natural killer (NK) cell activity was investigated in peripheral blood mononuclear cells of patients with leprosy. The NK activity of patients with borderline or lepromatous leprosy did not differ significantly from that of normal subjects. However, in a group of patients with lepromatous leprosy undergoing an episode of erythema nodosum leprosum (ENL), NK activity was significantly depressed. In four patients with ENL, NK activity was virtually abolished. Depressed NK activity could not be attributed to the effects of corticosteroid therapy, nor did a serum factor appear to be responsible. Evidence was obtained that depressed NK activity in patients with ENL was not due to dysfunction of the NK cells themselves; they functioned normally when separated from the individual's total mononuclear cell population. Additional cell depletion studies suggested that the patients' monocytes were responsible for the observed depression of NK activity.     

Cell-mediated immunity in amyloidosis secondary to lepromatous leprosy.

Cell-mediated immunity in lepromatous leprosy patients with and without amyloidosis has been studied. Amyloidosis occurred mostly in patients with a history of recurrent erythema nodosum leprosum (ENL) reactions. For this reason, two control groups of leprosy patients were included, one having a history of recurrent ENL and the other little or no ENL. The lack of responsiveness to lepromin in vivo and in vitro, characteristic of lepromatous leprosy, was not altered by the presence of amyloidosis or a history of ENL. No significant difference between the patient groups was observed in the response to PPD in vitro, but skin reactivity to PPD was significantly lower in the patients with amyloidosis than in those without amyloidosis. In contrast, the PHA responses of patients with amyloidosis were significantly higher than those of control patients without a history of ENL, but not significantly different from those of control patients with a history of recurrent ENL. Lepromatous leprosy patients who develop amyloidosis thus appear to belong to a group, susceptible to repeated attacks of ENL, whose PHA responses are higher than those of other lepromatous leprosy patients. The lower skin reactivity to PPD observed in the amyloid group may reflect a general impairment in delayed cutaneous hypersensitivity.     

CD1-positive epidermal Langerhans cells in skin reactions to autologous peripheral-blood-derived mononuclear cells in leprosy patients

A comparison was made on the characteristics of the infiltrates, the number and distribution of CD1-positive epidermal Langerhans cells (LC) at the sites of skin reaction induced by autologous peripheral-blood-derived mononuclear cells (PBMC) in leprosy patients. Clinically and histologically, the skin reaction was well expressed in tuberculoid patients as compared to lepromatous patients, erythema nodosum leprosum (ENL) patients and contacts. The quantum of lymphocytes in the infiltrates was maximal in the tuberculoid patients and it was minimal in lepromatous and ENL patients. The number and distribution of LC in the tuberculoid patients was significantly higher in the PBMC-inoculated sites as compared to control sites over 24 h. In contrast, no difference in the number and distribution of LC was noticed in the lepromatous and ENL patients. These observations indicate that the lymphocytes of tuberculoid patients in contrast to lepromatous leprosy patients are capable of sustenance in the local micro-environments of the skin and an effective interaction may be possible between LC and PBMC.     

Evidence of cell-mediated immune contrasuppression in lepromatous leprosy: modulation of a putative T contrasuppressor cell-subset.

Some lepromatous leprosy (LL) patients are characterized by the presence of activated suppressor T cells that specifically inhibit the immune response to Mycobacterium leprae antigens. Immune contrasuppressor (CS) cell activity antagonize suppressor function. Whereas the former function has been extensively studied in leprosy, the latter has not been explored. We studied the peripheral blood mononuclear cells (PBMNC) of 20 patients with leprosy (10 lepromatous and 10 tuberculoid) and six healthy contacts. We found CS-like activity in the PBMNC from some LL patients when assayed in vitro using lepromin as antigen. This CS-like function was found in CD8+, vicia villosa adherent (VV+) T cells. CS-like activity was not detected in PBMNC from either tuberculoid patients or healthy contacts. Pre-treatment of CD8+, VV+ cells with either recombinant IL-2 (5 u/ml) or recombinant interferon-gamma (1,000 u/ml) did not modify significantly their putative CS function. However, in 50% of lepromatous patients the pre-incubation of CD8+, VV+ cells with both lymphokines together increased significantly the CS-like activity. These data suggest that the in vitro immune response to M. leprae in some LL patients can be augmented by either modifying numerically the contrasuppressor T cells or activating them with lymphokines.