Hypothesis: an alternative pathway for the regulation of inflammation.

Regulation of inflammation is a crucial event since its alteration, such as in sepsis and chronic autoimmune (i.e. rheumatoid arthritis, lupus erythematosus) or infectious diseases (i.e. tuberculosis, leprosy), determines severe tissue damage. Although there is a general consensus that regulation of inflammation results from a balance between proinflammatory and antiinflammatory pathways, we arrived at the conclusion that well known chemoattractants/proinflammatory molecules such as bacterial formyl peptides or immune complexes (IC), could induce, paradoxically, strong antiinflammatory effects. Thus, we demonstrated that N-formyl-methionyl-leucyl-phenylalanine (FMLP) exerted a drastic antiinflammatory effect, inhibiting the secretion of tumor necrosis alpha (TNF-alpha) induced by lipopolysaccharides, a potent TNF-alpha inducer. We also determined that in human neutrophils FMLP and IC induced the downregulation of receptors for the Fc portion of IgG (FcgammaRII and FcgammaRIIIB). Moreover, FMLP inhibited interferon gamma (IFN-gamma)-induced FcgammaRI expression and IC downregulate class II molecules of the major histocompatibility complex on monocytes. Part of these effects were mediated by the release of aspartic-, serin-, or metalloproteases. All these results favor the postulation of a new concept on the regulation of inflammation carried out through an alternative and non conventional pathway, in which a chemoattractant/proinflammatory agent could, under certain circumstances, act as an antiinflammatory molecule.

IgM anti-phenolic glycolipid I and IgG anti-10-kDa heat shock protein antibodies in sera and immune complexes isolated from leprosy patients with or without erythema nodosum leprosum and contacts.

The aim of the present work was to evaluate the levels of anti-PGL-I and anti-10-kDa heat shock protein antibodies in serum and immune complexes isolated from leprosy patients, convivients and controls. Leprosy patients with erythema nodosum leprosum or without it were included and a comparative study was done to investigate intergroup differences. Immune complexes were precipitated from serum by polyethylene glycol 3.5%; antibody levels were measured in sera and in dissociated immune complexes by ELISA. Serum antibody levels were then correlated with immune complex-associated antibody levels. The results showed that the erythema nodosum leprosum group differed from controls, contacts and non-erythema patients in their immune complex levels. IgM anti-PGL-I and IgG anti-10-kDa heat shock protein antibodies were constituents of the immune complexes in patients with erythema nodosum leprosum, who exhibited a significant difference in their immune complex composition compared with controls, contacts and non-erythema patients; while free antibody levels (anti-PGL-I and anti-10-kDa) did not differentiate between erythema and non-erythema patients, the measurement of immune complex-associated antibodies demonstrated a significant difference between the two clinical conditions. Furthermore, the measurement of immune complex-associated anti-PGL-I IgM made it possible to differentiate between contacts and controls. The significance of these results is discussed.

Suppressive effect of circulating immune complexes from leprosy patients on the lymphocyte proliferation induced by M. leprae antigens in healthy responders.

The effect of circulating immune complexes, isolated in the form of polyethylene glycol (PEG) precipitates from leprosy patients, on lymphocyte proliferation was studied. The results obtained showed that PEG precipitates obtained from the borderline lepromatous/lepromatous (BL/LL) types of leprosy patients and those undergoing erythema nodosum leprosum (ENL) had significant suppressive effects on the lymphocyte proliferation induced by Mycobacterium leprae antigens in healthy responders. The percent decreases in the mean values of delta cpm in the presence of PEG precipitates from the BL/LL and ENL groups were found to be 46.8 +/- 22.4 and 65.0 +/- 24.3, respectively. However, no significant suppressive effects (except for ENL PEG precipitates) of these PEG precipitates were observed on the lymphocyte proliferation induced by tuberculin (PPD). Further, PEG precipitates alone (in the absence of M. leprae antigen) from the BL/LL and ENL groups were found to have no effect on the lymphocyte proliferation.

Immunological suppression by human CD8+ T cells is receptor dependent and HLA-DQ restricted.

Mechanisms of specific immunologic unresponsiveness or tolerance and their regulation by the major histocompatibility complex remain central issues in immunology. Recent findings that potentially reactive anti-self T cells are not completely clonally deleted in the thymus and that specific immunological unresponsiveness can be acquired in certain infectious diseases, such as leprosy, suggest that peripheral unresponsiveness can be developed and maintained in adults. Human antigen-specific T suppressor cells represent one mechanism of peripheral tolerance. Clones of CD8+ T suppressor cells have been derived from blood or lesions of patients with lepromatous leprosy who are selectively unable to mount cellular immunity to Mycobacterium leprae. Using a panel of M. leprae-specific CD4+ and CD8+ T-cell clones of differing major histocompatibility complex class II haplotypes, suppression in vitro was found to be restricted by HLA-DQ and not by HLA-DR and inhibited by antibodies to HLA-DQ. In addition, antigen-induced suppression could be inhibited by antibodies specific to appropriate polymorphic T-cell receptor beta chains of the CD8+ clones. The results establish that activation of specific T suppressor cells is dependent on their polymorphic T-cell receptors and suggest that HLA-DQ serves as the preferred restricting element for suppression.

The human C3b receptor: function and role in human diseases.

The human C3b receptor (CR1) is a polymorphic glycoprotein which functions regulating the complement system by inhibiting the activation of C3 and C5, through its effect on their convertases, and serving as cofactor for factor I in mediating the degradation of C3b to its inactive fragment C3bi and further to C3d-g. The latter are then ligands for their respective receptors on leukocytes, CR3 and CR2. Additionally, CR1 on erythrocytes endows these cells with the capacity to deliver immune complexes (IC) to the reticuloendothelial system, resulting in their clearance from the circulation. On phagocytes, this receptor participates in the process of endocytosis of foreign particles. There is a wide inherited variation of CR1 expression on erythrocytes (CR1/E) of different individuals. Patients with diseases which feature elevated levels of IC, such as systemic lupus erythematosus, leprosy, and AIDS, have a marked decrease of CR1/E, which may result in an altered clearance. This reduction appears to be related to disease activity, and the most probable site for CR1/E loss is during the transfer of IC to macrophages. Healthy neutrophils increase tenfold their expression of CR1 in response to the effect of chemoattractant peptides. Neutrophils from patients with AIDS display an altered response to stimulation. This defect may be of relevance in the process of endocytosis.

Activation of complement by circulating immune complexes isolated from leprosy patients.

Circulating immune complexes isolated from different types of leprosy sera as polyethylene glycol (PEG) precipitates were found to be efficient activators of the alternative pathway of complement. PEG precipitates from BL/LL leprosy patients and those with erythema nodosum leprosum were found to activate both the classical pathway and the alternative pathway of complement efficiently, while PEG precipitates from TT/BT leprosy patients and borderline tuberculoid patients in reaction were found to active the alternative pathway of complement but not the classical pathway. No significant differences were observed between the PEG precipitates from reactional and nonreactional TT/BT and BL/LL patients in their complement activating ability.

'Flu' syndrome on once monthly rifampicin: a case report.

'Flu' syndrome as a complication of intermittent weekly administration of rifampicin is well documented. The rare occurrence of 'flu' syndrome on once monthly rifampicin is reported in this paper.

Evaluation of circulating immune complexes in leprosy

Se investigó la presencia de complejos inmunes circulantes (CIC) en pacientes con lepra mediante 4 métodos de detección. Los pacientes se agruparon en: lepra lepromatosa con baciloscopía positiva (LL+), lepra lepromatosa con baciloscopía negativa (LL-), tuberculoide (TT) y contactos de primer grado (Co). Se incluyó un grupo control libre de enfermedad. Los métodos empleados para esta investigación fueron: 1) Test de combinación a 125I-C1q; 2) Test de agregación plaquetaria (PAT); 3) Test de preciptación en plietilenglicol al 3,5% (PEG 3,5%) y 4) Test de precipitación en (PEG 2,5%), ambas concentraciones finales. Los resultados fueron elevados cualesquiera fuero el método empleado; en LL- los valores de CIC fueron estadísticamente menores que en LL+, si bien al igual que TT y Co fueron diferentes que la población control. Se pudo comprobar la sensibilidad de diferentes técnicas empleadas, siendo el índice de correlación entre el test de combinación 125I-Cq y el PAT y el PATr = 0,90; entre C1q y el PEG 3,5%, r = 0,36; PEG 3,5% vs PATr = 0,48; PEG 2,5% vs PAT, r = 0,24 y PEG 2,5% vs Cq, r = 0,14. Los resultados demuestran que: a) Los métodos de elección para la deteccion de CIC en lepra son el de combinación a C1 radioactivo y el test de agregación plaquetaria. b) La preciptación en PEG al 2,5% disminuyen la sensibilidad del ensayo en relación al PEG 3,5%. c) Los niveles elevados de CIC en LL + se podrían deber a la carga antigénica demostrada por la baciloscopía positiva. d) Los niveles de CIC en los convivientes de primer grado, similares a los obtenidos en LL- y TT podrían atribuirse a una infección subclínica de ese grupo

Evaluation of circulating immune complexes in leprosy

Se investigó la presencia de complejos inmunes circulantes (CIC) en pacientes con lepra mediante 4 métodos de detección. Los pacientes se agruparon en: lepra lepromatosa con baciloscopía positiva (LL+), lepra lepromatosa con baciloscopía negativa (LL-), tuberculoide (TT) y contactos de primer grado (Co). Se incluyó un grupo control libre de enfermedad. Los métodos empleados para esta investigación fueron: 1) Test de combinación a 125I-C1q; 2) Test de agregación plaquetaria (PAT); 3) Test de preciptación en plietilenglicol al 3,5% (PEG 3,5%) y 4) Test de precipitación en (PEG 2,5%), ambas concentraciones finales. Los resultados fueron elevados cualesquiera fuero el método empleado; en LL- los valores de CIC fueron estadísticamente menores que en LL+, si bien al igual que TT y Co fueron diferentes que la población control. Se pudo comprobar la sensibilidad de diferentes técnicas empleadas, siendo el índice de correlación entre el test de combinación 125I-Cq y el PAT y el PATr = 0,90; entre C1q y el PEG 3,5%, r = 0,36; PEG 3,5% vs PATr = 0,48; PEG 2,5% vs PAT, r = 0,24 y PEG 2,5% vs Cq, r = 0,14. Los resultados demuestran que: a) Los métodos de elección para la deteccion de CIC en lepra son el de combinación a C1 radioactivo y el test de agregación plaquetaria. b) La preciptación en PEG al 2,5% disminuyen la sensibilidad del ensayo en relación al PEG 3,5%. c) Los niveles elevados de CIC en LL + se podrían deber a la carga antigénica demostrada por la baciloscopía positiva. d) Los niveles de CIC en los convivientes de primer grado, similares a los obtenidos en LL- y TT podrían atribuirse a una infección subclínica de ese grupo (AU)

Evaluation of circulating immune complexes in leprosy.

Circulating immune complexes (CIC) were evaluated in leprosy by 4 methods: the 125I-C1q binding assay (C1q), the platelet aggregation test (PAT), the 3.5% polyethylene glycol (PEG) precipitation test and the 2.5% PEG precipitation assay. Serum samples belonged to lepromatous leprosy bacilloscopy positive (LL+), lepromatous leprosy bacilloscopy negative (LL-), tuberculoid (TT) and first grade contact group (Co). Studies performed by the 3 first methods showed higher CIC levels in LL+ group (p less than 0.01) and lower values in the 3 others, all of them when compared to normals. On the contrary, the 2.5% PEG precipitation test gave less discriminative results giving only p less than 0.01 in LL+. CIC values obtained in the contact group showed significant results compared to normals but similar to LL- and TT groups. The C1q binding assay and the PAT were the most discriminative methods giving r = 0.90; C1q versus 3.5% PEG, r = 0.36; C1q vs 2.5% PEG, r = 0.14. The PAT compared to 3.5% PEG, r = 0.48 and PAT vs. 2.5% PEG, r = 0.24. Therefore it may be concluded as follows: a) The radioiodinated C1q binding assay and the PAT are recommended for the study of CIC in leprosy; b) The 2.5% PEG precipitation assay offers less sensitivity since it gave similar value in LL-, TT, Co and controls; c) CIC levels observed in LL+ patients may be induced by the antigenic overload demonstrated by the positive bacilloscopy; d) The contacts have CIC levels significantly different from the normal population possibly caused by a subclinical infection.

Effect of in vitro formed immune complexes on macrophage functions of Mycobacterium leprae infected mice.

Nonspecific macrophage functions were studied in Mycobacterium leprae infected and preformed immune complex (IC) administered normal (NI) and thymectomized/irradiated (TRI) mice at different time periods. Uninfected controls given IC were also included. Significant decrease in the chemotaxis, phagocytosis and bactericidal activities of macrophages obtained from infected groups compared to their controls were observed. Phagocytic and chemotactic activities of macrophages were normal but intracellular killing was seen to be depressed in studies conducted in normal and thymectomized immunosuppressed groups (Vaishnavi et al., 1985, Kumar et al, 1987) which were not administered with preformed IC.

Role of immune complexes in alteration of lymphocyte subpopulation numbers and functions in experimental leprosy.

Swiss albino mice (normal as well as thymectomised and irradiated were inoculated into the footpads with Mycobacterium leprae and divided into two main phases of study. Phase I comprised of animals not given preformed immune complexes (IC). Uninfected controls were however included. Phase II consisted of animals given in vitro prepared IC at zero day period (OdIC), three month period (3mIC) or six month period (6mIC) to both uninfected and infected groups. Splenic lymphocytes were isolated to quantify T and B cells and their responses to M. leprae antigen and four different mitogens. Significant decrease in T cell counts and blast transformation was seen in the M. leprae infected animals which were also administered with immune complexes. Immunosuppression by IC was therefore seen to be enhanced in the presence of M. leprae infection.

Detection of mycobacterial antigens in leprosy serum immune complex.

The antigens from immune complexes of sera from patients with mycobacterial diseases were released by sodium dodecyl sulfate. The antigenic activity of the released proteins was tested by agar gel diffusion and immunoelectrophoresis. This simple method provided direct evidence for the presence of mycobacterial antigens in the immune complexes of sera from patients with leprosy and tuberculosis.