Thymus-dependent lymphocytes of peripheral blood in leprosy patients

A Systematic Review of Immunological Studies of Erythema Nodosum Leprosum

Erythema nodosum leprosum (ENL) is a painful inflammatory complication of leprosy occurring in 50% of lepromatous leprosy patients and 5-10% of borderline lepromatous patients. It is a significant cause of economic hardship, morbidity and mortality in leprosy patients. Our understanding of the causes of ENL is limited. We performed a systematic review of the published literature and critically evaluated the evidence for the role of neutrophils, immune complexes (ICs), T-cells, cytokines, and other immunological factors that could contribute to the development of ENL. Searches of the literature were performed in PubMed. Studies, independent of published date, using samples from patients with ENL were included. The search revealed more than 20,000 articles of which 146 eligible studies were included in this systematic review. The studies demonstrate that ENL may be associated with a neutrophilic infiltrate, but it is not clear whether it is an IC-mediated process or that the presence of ICs is an epiphenomenon. Increased levels of tumor necrosis factor-α and other pro-inflammatory cytokines support the role of this cytokine in the inflammatory phase of ENL but not necessarily the initiation. T-cell subsets appear to be important in ENL since multiple studies report an increased CD4⁺/CD8⁺ ratio in both skin and peripheral blood of patients with ENL. Microarray data have identified new molecules and whole pathophysiological pathways associated with ENL and provides new insights into the pathogenesis of ENL. Studies of ENL are often difficult to compare due to a lack of case definitions, treatment status, and timing of sampling as well as the use of different laboratory techniques. A standardized approach to some of these issues would be useful. ENL appears to be a complex interaction of various aspects of the immune system. Rigorous clinical descriptions of well-defined cohorts of patients and a systems biology approach using available technologies such as genomics, epigenomics, transcriptomics, and proteomics could yield greater understanding of the condition.

Cytogenetic studies in leprosy patients before and after chemotherapy

The frequencies of chromosome aberrations and sister chromatid exchanges (SCEs), cell proliferation kinetics and mitotic indices were studied in peripheral blood lymphocyte cultures of leprosy patients both before and after chemotherapy. The differences in the frequencies of chromosome aberrations and SCEs between controls, paucibacillary and multibacillary patients were found to be statistically highly significant (P less than 0.001). The extent of cytogenetic damage seemed to depend on the severity of the disease. Lymphocytes of untreated leprosy patients showed a low mitotic index and a slow rate of cell proliferation. Following combined treatment with dapsone and rifampicin there was an increase, but to a lesser degree (P less than 0.01), in the frequency of SCEs and chromosome aberrations while the drug combination of dapsone, rifampicin and clofazamine had a nonmutagenic effect on chromosomes of the patient. Furthermore, after drug treatment, the cell proliferation rate and mitotic indices in paucibacillary patients were comparable to that of controls. These results indicate the clastogenic potency of Mycobacterium leprae and the remedial effects that follow therapeutic drug treatment.

Determination of different populations of blood lymphocytes in Brazilian patients with hanseniasis

The number of B and T lymphocytes were determined in the blood of 35 Brazilian patients with leprosy: 19 lepromatous (L), 9 borderline (B), 4 tuberculoid (T), and 3 indeterminate (I) and also in a control group of 30 normal individuals. The results, were as follows. B lymphocytes, no differences between the patients with hanseniasis and the control group; T lymphocytes, there was an evident depletion in the patients with L compared to the control group and patients with T; and the average of T lymphocytes in B and I was lower than that seen in the control group and in patients with T. Despite this alteration they approach to what is found in the patients with T and the control group.

Immunoprofile of reactions in leprosy

The immunologic profile during erythema nodosum leprosum (ENL) revealed increased percentage and absolute count of B-lymphocytes, in addition to considerably lowered levels of complement component C3. Serum immunoglobulins--IgG, IgA, and IgM--were significantly raised after subsidence of ENL, whereas upgrading reaction showed an increase of absolute count of total T lymphocytes and percentage and count of B-lymphocytes. In addition, a raised serum IgM level was noted after regression of ENL. Downgrading reaction demonstrated a decreased percentage of early T-lymphocytes and raised the absolute count of B-lymphocytes. Serum IgA levels were found to be increased after amelioration of ENL.

Mechanism of immunosuppression in leprosy: presence of suppressor factor(s) from macrophages of lepromatous patients

Human peripheral blood mononuclear cell proliferation induced by Mycobacterium leprae could be inhibited by the suppressor factor in the lysate of the macrophages of lepromatous leprosy patients. Macrophages from normal subjects and tuberculoid patients did not show production of a suppressor factor. Inhibition occurred only when the factor was present in the initial stages of lymphocyte culture. The factor is heat stable and nondialyzable. Proliferation induced by some mycobacteria and concanavalin A could also be blocked by the factor. Interestingly, blastogenic response by a few other antigens and phytohemagglutinin could not be inhibited by the suppressor factor. Mononuclear cells pretreated with such lysate from lepromatous macrophages for 24 h could induce suppressive activity in the cells in vitro in an autologous system. Treatment of these cells with carbonyl iron after the induction phase, to remove phagocytic cells, did not abolish their suppressive activity. The lepromatous macrophage lysate also generated suppressive activity in a T-lymphocyte-enriched population of normal subjects. These studies are interpreted to indicate that immunosuppression in lepromatous patients is produced by both macrophages and T lymphocytes. The exact phase in which either of these cells acts as a suppressor may be different. Specific suppression by macrophages to M. leprae can be an early event, and nonspecific suppression by T lymphocytes may be a later event in the course of lepromatous leprosy.

Effect of Mycobacterium leprae on lymphocyte proliferation: suppression of mitogen and antigen responses of human peripheral blood mononuclear cells

Evidence is presented that Mycobacterium leprae suppresses the in vitro proliferative response of human peripheral blood mononuclear cells (PBM) to antigen and mitogen. Lymphoproliferation induced by PPD or alloantigen stimulation was inhibited by concentrations of M. leprae which were not cytotoxic for lymphoblasts. In contrast, the inhibition of mitogen-stimulated PBM was seen only at higher concentrations of M. leprae which proved to be cytotoxic for lymphoblasts. The inhibitory effect was found not to be dependent on a particular cell population present in leprosy patients, as PBM from normal were inhibited similarly. These findings may explain some of the immunological aberrations observed in lepromatous leprosy patients who harbour large numbers of M. leprae bacilli in their tissues.

Numerical changes in T cell subsets (T gamma and T mu) in leprosy patients

Eighty-six leprosy patients (49 active lepromatous, 24 inactive lepromatous 7 borderline, and 6 tuberculoid) and nine healthy controls were examined for numerical changes in T cell subsets (T gamma and T mu), and complement levels in peripheral blood to determine the roles of T cell subsets and complement in the etiology of leprosy. The percentage and number of T gamma and T mu showed no significant differences among the different clinical groups, but 4 out of 49 active lepromatous, 3 out of 24 inactive lepromatous and 3 out of 7 borderline cases showed a high prcentage of T gamma cells. Serum concentrations of C4, C3c, and C3 activator, an important factor in the alternative pathway of complement activation, were not significantly different among the groups. However, C3 activator and C3c concentrations were significantly high in active lepromatous patients complicated by an immune complex disease called "erythema nodosum leprosum" (ENL) compared with ENL-free active lepromatous leprosy.

Surface markers on lymphocytes and cells of the mononuclear phagocyte series in skin sections in leprosy

E, EA and EAC rosetting techniques and Ig fluorescence were used in a study of receptor sites in cryostat sections of lesions through the spectrum of leprosy, and for comparison in some other mycobacterial and granulomatous lesions. Anti-C3, and trypsin were used as blocking agents. Lymphocytes in borderline lepromatous leprosy produced EA adherence and IgG fluorescence indicating B type cells. Lymphocytes in tuberculoid leprosy produced neither E or EA adherence and no fluorescence; these cells were presumed to be T cells. EAC and EA adherence was more marked in areas of macrophage infiltration, where there were few lymphocytes, than over the lympocytes themselves. Two distinct patterns emerged: (i) EA binding together with IgG fluorescence was seen in active lepromatous leprosy and could be localised to the surface of individual macrophages, and (ii) EAC binding together with IgM fluorescence was seen in the granuloma of tuberculoid leprosy and sarcoidosis, but could not be definitely related to cell surface; rather it was diffusely spread over the whole granuloma; EAC adherence was diminished by anti-C3 serum. Trypsin removed EA binding completely, but only diminished EAC adherence. It is suggested that the EA pattern indicates immunoglobulin receptors on macrophage and lymphocyte surfaces: and that the EAC binding (which is stronger than EA) involves C3 and IgM receptors at extracellular sites as well as C3 receptor sites on epithelioid cell surfaces. EA and EAC binding were enhanced in borderline tuberculoid leprosy in reaction and erythema nodosum leprosum, suggesting that immunoglobulin and complement receptor sites increase in number with enhanced hypersensitivity.

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.

Effect of levamisole on Mycobacterium leprae in mice

Levamisole, an antihelminthic drug that is capable of enhancing immune responses in mice and in humans, was tested in experimental Mycobacterium leprae infections in mice by a number of schedules. Intermittent schedules were used, and administration of the drug was started (i) around the time of inoculation with M. leprae, (ii) when the M. leprae population was approaching the plateau level, (iii) after the onset of the plateau phase, or (iv) after BCG vaccination 28 days following the inoculation with M. leprae. No effect of drug could be discerned with any of the schedules.

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.

Antibody-mediated immunity in CFW mice infected with Mycobacterium lepraemurium. Humoral immune response in murine leprosy

A depression in antibody-mediated immunity (AMI) measured both in terms of circulating antibody and plaque-forming cells in the spleen was observed in CFW mice infected with M. lepraemurium when sheep red blood cells (SRBC) and human gammaglobulin (HGG) were used as antigens. The impairment in AMI was evident only after 75 days of infection thereafter the antibody response to SRBC antigen progressively decreased until the last day of experimentation (135 days). Within the first 60 days of infection no alteration in AMI was observed with the HGG antigen while the response to the SRBC antigen was significantly higher in the infected animals than in uninfected controls.

T and CR+ lymphocyte profile in leprosy and the effect of treatment

Thymus-derived lymphocytes (T lymphocytes) and complement receptor-bearing lymphocytes (CR+ lymphocytes) were estimated by using erythrocyte rosettes and erythrocyte-antibody-complement rosettes as markers in untreated lepromatous and untreated tuberculoid patients and in healthy controls. Treated lepromatous cases were also investigated. Ten cases of untreated lepromatous patients were reassessed 6 months or more after therapy commenced. A significant decrease in both percentages and absolute numbers of CR+ cells in the untreated lepromatous leprosy subjects was observed. This decrease showed a return to normal levels after treatment. The percentage of T cells in the untreated lepromatous cases was normal; however, the absolute numbers of T cells and the total lymphocyte count showed a significant decrease. After therapy, the T cell population was unchanged but the total number of lymphocytes increased significantly with treatment. The absolute number of T and CR+ cells was significantly less in the untreated than in the treated lepromatous patients.

Studies on the subpopulation and function of peripheral lymphocytes, and inhibitor to PHA stimulation existing in the serum of patients with liver disease

In our recent report we observed the abnormal response to PHA stimulation in the peripheral lymphocytes of patients with chronic liver diseases. The present report concerns extensive studies of this earlier report; analysis of the subpopulation and function of peripheral lymphocytes in patients with liver diseases. PHA responsiveness in acute hepatitis was reduced in the acute phase and improved during the convalescent stage. In chronic liver disease, half of the patients showed a decrease in T-cell population as well as a reduced response to PHA stimulation. These phenomena were observed more frequently in HBs-antigen positive patients than in HBs-antigen negative cases. Furthermore, we found the existence of an inhibitor to PHA response in the serum of 8 cases among 19 patients with various liver diseases. In patients with such a serum inhibitor, the reactivity of the lymphocyte itself to PHA was considerably higher but the T-cell population was much more decreased than that of inhibitor negative cases.