Differential immunoglobulin and complement levels in leprosy prior to development of reversal reaction and erythema nodosum leprosum.

BACKGROUND: Leprosy is a treatable infectious disease caused by Mycobacterium leprae. However, there is additional morbidity from leprosy-associated pathologic immune reactions, reversal reaction (RR) and erythema nodosum leprosum (ENL), which occur in 1 in 3 people with leprosy, even with effective treatment of M. leprae. There is currently no predictive marker in use to indicate which people with leprosy will develop these debilitating immune reactions. Our peripheral blood mononuclear cell (PBMC) transcriptome analysis revealed that activation of the classical complement pathway is common to both RR and ENL. Additionally, differential expression of immunoglobulin receptors and B cell receptors during RR and ENL support a role for the antibody-mediated immune response during both RR and ENL. In this study, we investigated B-cell immunophenotypes, total and M. leprae-specific antibodies, and complement levels in leprosy patients with and without RR or ENL. The objective was to determine the role of these immune mediators in pathogenesis and assess their potential as biomarkers of risk for immune reactions in people with leprosy. METHODOLOGY/FINDINGS: We followed newly diagnosed leprosy cases (n = 96) for two years for development of RR or ENL. They were compared with active RR (n = 35), active ENL (n = 29), and healthy household contacts (n = 14). People with leprosy who subsequently developed ENL had increased IgM, IgG1, and C3d-associated immune complexes with decreased complement 4 (C4) at leprosy diagnosis. People who developed RR also had decreased C4 at leprosy diagnosis. Additionally, elevated anti-M. leprae antibody levels were associated with subsequent RR or ENL. CONCLUSIONS: Differential co-receptor expression and immunoglobulin levels before and during immune reactions intimate a central role for humoral immunity in RR and ENL. Decreased C4 and elevated anti-M. leprae antibodies in people with new diagnosis of leprosy may be risk factors for subsequent development of leprosy immune reactions.

Comprehensive evaluation of complement components in the course of type I (Lepra) and type II (ENL) reactions.

Complement components C1q and C4 of classic pathway; C3d, a breakdown product of C3, and factor B of alternate pathway: and C3, a component both of classic and alternate pathways, were studied in 35 patients, comprising 18 type I (Lepra) and 17 type II (ENL) reactions. There was a significant decrease in C3 and factor B with a concomitant rise of C3d during ENL. These changes indicate their preeminent role in immunogenesis of type II (ENL) reaction. The changes in the classic pathway components, on the other hand, were insignificant, apparently suggesting its limited involvement in ENL. Furthermore, reversion of factor B and C3d after subsidence of reaction is intriguing and may indicate that they are not substantially affected even with contemporary treatment. Complement components, of both classic and alternate pathways, showed no significant alterations either during type I (Lepra) reaction or after its amelioration.

Solubilization of preformed immune complexes in sera of patients with type 1 and type 2 lepra reactions.

Serum complement activity in leprosy patients has been studied using solubilization of preformed immune complexes as an index. The solubilization capacity of sera from lepromatous patients with or without erythema nodosum leprosum (ENL) as well as from type 1 reactional patients was found markedly reduced as compared to controls. Solubilization did not improve at all in the ENL patients after remission of the reaction phase. The addition of fresh normal sera failed to bring about any significant restoration of solubilizing capacity of the deficient sera. Mycobacterium leprae sonicate significantly reduced the solubilization capacity. Our results suggest that circulating mycobacterial breakdown products possibly interfered with the capacity of the ENL patients' sera to solubilize immune complexes.

Serum immune complexes in erythema nodosum leprosum reactions of leprosy.

Serum estimations of immunoglobulins, complement components and their presence in circulating immune complexes were carried out in 39 Lepromatous, 44 ENL and 22 Post ENL leprosy patients. Serum IgG, IgA, IgM, C3 and C4 levels were determined by single radial immunodiffusion. Serum immune complexes were precipitated with Polyethylene Glycol (PEG) and IgG, IgA, IgM, C3 and C4 were estimated by single radial immunodiffusion and expressed as % of precipitation of their serum level. Decreased IgG, IgM; increased IgA and C3; and no change in C4 levels are observed in ENL than Lepromatous and Post ENL patients. However, a gradual insignificant reduction of IgG, IgA, and IgM was found from Lepromatous to ENL and Post ENL patients in the PEG-precipitates. Similarly, C3 and C4 was found reduced insignificantly in ENL than Lepromatous and Post ENL patients. The significance of these estimations in relation to immune status of ENL reactions are discussed.

Breakdown product of factor B as an index of complement activation in lepromatous leprosy and its relation with bacillary load.

Serum complement profile studied in 50 lepromatous leprosy patients with various bacillary loads demonstrated significantly decreased C3 levels in patients with high bacteriological index (2+ to 4+) as compared with those with lesser bacterial load. In contrast, mean serum levels of C1q and C4 components remained unchanged. The concentration of factor B breakdown product (Ba) and its ratio to factor B increased with the bacterial density and more so in patients with erythema nodosum leprosum. A significant negative correlation was found between serum C3 and Ba levels in most lepromatous patients. Analysis of the data suggested the alternative pathway as the possible mechanism of complement activation in lepromatous leprosy.

[Immune complexes and complement in leprosy (author's transl)]. / Les complexes immuns et le complément dans la lèpre.

The sera of 87 Senegalese patients with various forms of leprosy were investigated. Two of the most reliable methods were used to detect circulating immune complexes : the radiolabelled C1q binding test and the Raji cell binding technique. Several fractions of complement, including C3, C4, factor B and the C3d product of C3 were also assayed. A material having the properties of immune complexes was detected in lepromatous and reactional leprosy. In tuberculous leprosy, only the Raji cell binding technique gave positive results. C3 and C4 were normal or slightly raised, but C3d was increased in all forms of the disease. There was no significant correlation between C3d values and the results of immune complexes detection tests.

On the significance of C2, C4, and factor B polymorphisms in disease.

In this review article, recent evidence is presented that some diseases like insulin-dependent diabetes mellitus, multiple sclerosis, and idiopathic membranous nephropathy, which are primarily associated with HLA-D,DR, are also related to the rare C2, C4, and Factor B alleles. Circumstantial evidence is available that at least some of these rare variants may be functionally deficient. Based on the concept of functionally interacting gene clusters, mutant complement genes may lead to impaired effector mechanisms in virus neutralization or lysis of virus-infected cells. Other mechanisms such as alteration of vascular permeability may be involved in the development of proliferative retinopathy and familial hypertension. In lepromatous lepra, an impaired cell-mediated lysis of M. leprae may be related to the hemolytically inactive C4F1 allelic product.

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.

In vitro synthesis of humoral factors (immunoglobulins and complement) in lesional skin of leprosy patients.

An in vitro culture technique was used to demonstrate the synthesis of immunoglobulins and complement in lesional skin of patients representing the entire clinico-histopathological spectrum of leprosy. The results indicate that immunoglobulin G is produced in different amounts in the various forms of leprosy. Classification of the patients according to the three main groups shows that a small amount of immunoglobulin G synthesis occurred in tuberculoid leprosy, a distinct amount occurred in borderline leprosy, and large amount occurred in lepromatous leprosy. Contrary to expectation, synthesis of C3 was found only in some of the cultures of these three forms of leprosy. The function of the locally synthesized immunoglobulin G and the findings concerning C3 synthesis are discussed.

Serum complement profile in human leprosy and its comparison with immune complex diseases.

In the present study we have estimated the serum levels of early, middle, and distal complement components, e.g., Clq, C3, C4, C5, C8, and C9 along with C1-inactivator and CH50 in patients with tuberculoid and lepromatous leprosy and have compared these results with the levels in healthy subjects as well as with levels in patients with other immune complex diseases. We have also analyzed the cryoglobulins present in the sera of these patients; they consisted of either a single or mixed IgG, IgA, IgM or fibrinogen in most instances. The component C3 was found in only one sample. It appears that unlike lupus nephritis, in which complement is activated by direct path in which complement is activated by direct path in about 30% to 50% of leprosy patients, significant C3 complement consumption takes place primarily via the alternate pathway and is probably initiated by the aggregated immunoglobulins represented in cryoprecipitates. This is further supported by the study of serum factor B and its breakdown product (Ba) in these patients. The question of the role of the middle and distal complement components, such as C5, C8 and C9, during total hemolytic complement and C3 consumption in leprosy remains unanswered.

Complement determinations in the synovial fluid and serum of a patient with Erythema nodosum leprosum.

Simultaneous serum and synovial fluid CH50, C1, C4, C2, C1 esterase inhibitor and C3 protein were determined in a patient with acute erythema nodosum leprosum. The pattern of synovial fluid complement activity coupled with the demonstration of multiple lepra bacilli free and within histiocytes is more consistent with an infectious than an immune complex induced synovitis.

Biochemical, immunological and genetic studies in leprosy. II. Profile of immunoglobulins, complement components and C-reactive protein in sera of leprosy patients and healthy controls.

Various classes of immunoglobulins (IgA, IgM, IgG, IgD and IgE), complement components (C3 and C4) and C-reactive protein (CRP) were estimated in sera from normal healthy controls and leprosy (lepromatous and tuberculoid) patients from Ethiopia. Higher levels of IgA, IgM, IgG and IgD were found in lepromatous leprosy compared with normal healthy people while in tuberculoid leprosy only IgM, IgG and IgD levels were increased. Borderline leprosy patients showed increase in IgG level only. Although an increase in IgE was noted in lepromatous leprosy, it was not significant; the variations in IgE levels could be due to different socioeconomic background and exposure to intestinal parasites. C3 component was significantly reduced in leprosy patients compared with healthy controls while no difference in C4 component was observed. The results point towards an involvement of the "alternate pathway". A positive test against C-reactive protein antiserum was given by about 20% of the normal healthy controls while more than 60% lepromatous and tuberculoid leprosy patients were CRP positive. The results are discussed in relation to the status of immunoglobulins and complement components in leprosy and possible factors (environmental and genetic) which might affect them.