The cutaneous infiltrates of leprosy: cellular characteristics and the predominant T-cell phenotypes

"Doubt No More": Two Sizes Fit All

This Pillars of Immunology article is a commentary on “Differing lymphokine profiles of functional subsets of human CD4 and CD8 T cell clones,” a pivotal article written by P. Salgame, J. S. Abrams, C. Clayberger, H. Goldstein, J. Convit, R. L. Modlin, and B. R. Bloom, and published in Science, in 1991. https://www.science.org/doi/10.1126/science.254.5029.279.

Leptin Deficiency May Influence the Divergence of Cell-Mediated Immunity Between Lepromatous and Tuberculoid Leprosy Patients

Leprosy is a disease caused by an intracellular bacillus bacterium called Mycobacterium leprae which lives and multiplies in the hosts' macrophages and Schwann cells. Depending on the degree of the host's cell-mediated immunity (CMI) response to the bacilli, the disease manifests itself in five clinical spectra ranging from polar tuberculoid (TT) to polar lepromatous leprosy (LL). A very high level of T helper 1 (Th1) driven bacilli-specific CMI is seen in the TT form, whereas this response is essentially nonexistent in the LL form. As a result, there is very low or absent bacillary load and localized nodular lesions in TT patients. On the contrary, LL patients presented with high bacillary load and generalized lesions due to low CMI response. The mechanism underlying this divergence of CMI response is not clearly elucidated yet. However, mounting evidence links it to an elevated number of Th1 and Th17 suppressing CD4+ CD25+ FOXP3+ T regulatory cells (Treg cells) which are abundantly found in LL than in TT patients. The predominance of these cells in LL patients is partly attributed to a deficiency of leptin, the cytokine-like peptide hormone, in these patients. Becausea normal level of leptin promotes the proliferation and preferential differentiation of effector T cells (Th1 and Th17) while inhibiting the growth and functional responsiveness of the Treg cells. In contrast, leptin deficiency or neutralization was reported to exert the opposite effect on Treg cells and effector T cells. Other smaller subsets of lymphocytes such as gamma delta (γδ) T cells and B regulatory cells are also modulated by leptin level in the pathogenesis of leprosy. Leptin may therefore regulate the divergence of CMI between TT and LL patients by regulating the homeostasis of effector T cells and Treg cells, and this review will examine the underlying mechanism for this.

Immunological biomarkers of subclinical infection in household contacts of leprosy patients

Hansen's disease (or leprosy) still persists as a serious public health issue. Its diagnosis is based primarily on the detection of clinical signs that are characteristic of the disease. Studies have pointed to the selection of a set of serological and cellular biomarkers of subclinical infection that result in an efficient diagnosis. The aim of this study was compare index cases and their household contacts to identify differentially expressed biomarkers of immune response in leprosy that could provide reliable evidence of subclinical infection in household contacts. The study population consisted of index cases with multibacillary form (IC, n = 13) and their household contacts (HC, n = 14). Serum cytokines and chemokines were quantified using the cytometric beads array (CBA) system. The humoral response was assessed by ELISA test. Flow cytometry was used to characterize the cellular immune response. Monocyte and CD4 + T lymphocytes frequency was significantly higher in IC. Both CD4+ and CD8 + T lymphocytes had a reduced CD25 expression in HC. The immunoglobulin (Ig)M profile anti- NDO-HSA, LID-1, and NDOLID antigens was significantly higher in IC. This study points to the monocyte and CD4+ lymphocyte frequency, as well as specific IgM profile, as predictors of subclinical infection in the household contacts.

IL-26 contributes to host defense against intracellular bacteria

IL-26 is an antimicrobial protein secreted by Th17 cells that has the ability to directly kill extracellular bacteria. To ascertain whether IL-26 contributes to host defense against intracellular bacteria, we studied leprosy, caused by the obligate intracellular pathogen Mycobacterium leprae, as a model. Analysis of leprosy skin lesions by gene expression profiling and immunohistology revealed that IL-26 was more strongly expressed in lesions from the self-limited tuberculoid compared with expression in progressive lepromatous patients. IL-26 directly bound to M. leprae in axenic culture and reduced bacteria viability. Furthermore, IL-26, when added to human monocyte-derived macrophages infected with M. leprae, entered the infected cell, colocalized with the bacterium, and reduced bacteria viability. In addition, IL-26 induced autophagy via the cytoplasmic DNA receptor stimulator of IFN genes (STING), as well as fusion of phagosomes containing bacilli with lysosomal compartments. Altogether, our data suggest that the Th17 cytokine IL-26 contributes to host defense against intracellular bacteria.

Analysis of clinical data and T helper 1/T helper 2 responses in patients with different clinical forms of leprosy

INTRODUCTION:

Currently, there are no laboratory tests or sensitive and specific molecular markers for the early diagnosis of leprosy. The aim of this study was to analyze the clinical characteristics of patients with leprosy and investigate their immunological profile, comparing this with the type of lesion and the presence or absence of a Bacillus Calmette-Guérin (BCG) vaccination scar.

METHODS:

Statistical analyzes were performed by employing comparative tests (Pearson´s chi-square) to evaluate the variables in different clinical forms, considering significance at the 5% level.

RESULTS:

The study identified a predominance of lepromatous leprosy (26.9%) in patients aged between 34-53 years. Caucasians predominantly had borderline tuberculoid (BT) clinical forms (42%); a predominance of males with borderline lepromatous (19%) and lepromatous leprosy (26.9%) forms was observed; and the presence of BCG vaccination scars (27.5%) and lower limb nerves were more affected (38%) predominantly in the BT clinical form. Significant differences were identified, which included hypochromic lesions predominantly in the BT clinical form (24%); diffuse-type lesions predominantly in the tuberculoid (TT) clinical form (28%); ill-defined lesion border dominance in lepromatous leprosy (LL) clinical forms (30%); an irregular lesion limit predominantly in LL clinical forms (32%); and a predominant Th1 immune response in the BT clinical form (41.7%).

CONCLUSIONS:

The evaluation of the immunological profile in leprosy patients may contribute to the more detailed diagnosis and possibly better characterization of the prognosis for these individuals.

Distinct regions of the large extracellular domain of tetraspanin CD9 are involved in the control of human multinucleated giant cell formation

Multinucleated giant cells, formed by the fusion of monocytes/macrophages, are features of chronic granulomatous inflammation associated with infections or the persistent presence of foreign material. The tetraspanins CD9 and CD81 regulate multinucleated giant cell formation: soluble recombinant proteins corresponding to the large extracellular domain (EC2) of human but not mouse CD9 can inhibit multinucleated giant cell formation, whereas human CD81 EC2 can antagonise this effect. Tetraspanin EC2 are all likely to have a conserved three helix sub-domain and a much less well-conserved or hypervariable sub-domain formed by short helices and interconnecting loops stabilised by two or more disulfide bridges. Using CD9/CD81 EC2 chimeras and point mutants we have mapped the specific regions of the CD9 EC2 involved in multinucleated giant cell formation. These were primarily located in two helices, one in each sub-domain. The cysteine residues involved in the formation of the disulfide bridges in CD9 EC2 were all essential for inhibitory activity but a conserved glycine residue in the tetraspanin-defining 'CCG' motif was not. A tyrosine residue in one of the active regions that is not conserved between human and mouse CD9 EC2, predicted to be solvent-exposed, was found to be only peripherally involved in this activity. We have defined two spatially-distinct sites on the CD9 EC2 that are required for inhibitory activity. Agents that target these sites could have therapeutic applications in diseases in which multinucleated giant cells play a pathogenic role.

Differential dermal expression of CCL17 and CCL18 in tuberculoid and lepromatous leprosy

BACKGROUND

Leprosy is characterized by polar clinical, histologic and immunological presentations. Previous immunologic studies of leprosy polarity were limited by the repertoire of cytokines known at the time.

METHODOLOGY

We used a candidate gene approach to measure mRNA levels in skin biopsies from leprosy lesions. mRNA from 24 chemokines and cytokines, and 6 immune cell type markers were measured from 85 Nepalese leprosy subjects. Selected findings were confirmed with immunohistochemistry.

PRINCIPAL RESULTS

Expression of three soluble mediators (CCL18, CCL17 and IL-10) and one macrophage cell type marker (CD14) was significantly elevated in lepromatous (CCL18, IL-10 and CD14) or tuberculoid (CCL17) lesions. Higher CCL18 protein expression by immunohistochemistry and a trend in increased serum CCL18 in lepromatous lesions was observed. No cytokines were associated with erythema nodosum leprosum or Type I reversal reaction following multiple comparison correction. Hierarchical clustering suggested that CCL18 was correlated with cell markers CD209 and CD14, while neither CCL17 nor CCL18 were highly correlated with classical TH1 and TH2 cytokines.

CONCLUSIONS

Our findings suggest that CCL17 and CCL18 dermal expression is associated with leprosy polarity.

Leprosy: review of the epidemiological, clinical, and etiopathogenic aspects - part 1

Leprosy is caused by Mycobacterium leprae and has been known since biblical times. It is still endemic in many regions of the world and a public health problem in Brazil. The prevalence rate in 2011 reached 1.54 cases per 10,000 inhabitants in Brazil. The mechanism of transmission of leprosy consists of prolonged close contact between susceptible and genetically predisposed individuals and untreated multibacillary patients. Transmission occurs through inhalation of bacilli present in upper airway secretion. The nasal mucosa is the main entry or exit route of M. leprae. The deeper understanding of the structural and biological characteristics of M. leprae, the sequencing of its genome, along with the advances in understanding the mechanisms of host immune response against the bacilli, dependent on genetic susceptibility, have contributed to the understanding of the pathogenesis, variations in the clinical characteristics, and progression of the disease. This article aims to update dermatologist on epidemiological, clinical, and etiopathogenic leprosy aspects.

A journey in science: promise, purpose, privilege

Real innovations in medicine and science are historic and singular; the stories behind each occurrence are precious. At Molecular Medicine we have established the Anthony Cerami Award in Translational Medicine to document and preserve these histories. The monographs recount the seminal events as told in the voice of the original investigators who provided the crucial early insight. These essays capture the essence of discovery, chronicling the birth of ideas that created new fields of research; and launched trajectories that persisted and ultimately influenced how disease is prevented, diagnosed, and treated. In this volume, the first Cerami Award Monograph, by Carl Nathan, MD, chairman of the Department of Microbiology and Immunology at Weill Cornell Medical College, reflects towering genius and soaring inspiration.

Leprosy: an overview of pathophysiology

Leprosy, also known as Hansen's disease, is a chronic infectious disease caused by Mycobacterium leprae, a microorganism that has a predilection for the skin and nerves. The disease is clinically characterized by one or more of the three cardinal signs: hypopigmented or erythematous skin patches with definite loss of sensation, thickened peripheral nerves, and acid-fast bacilli detected on skin smears or biopsy material. M. leprae primarily infects Schwann cells in the peripheral nerves leading to nerve damage and the development of disabilities. Despite reduced prevalence of M. leprae infection in the endemic countries following implementation of multidrug therapy (MDT) program by WHO to treat leprosy, new case detection rates are still high-indicating active transmission. The susceptibility to the mycobacteria and the clinical course of the disease are attributed to the host immune response, which heralds the review of immunopathology of this complex disease.

Mycobacterium leprae-host-cell interactions and genetic determinants in leprosy: an overview

Leprosy, also known as Hansen's disease, is a chronic infectious disease caused by Mycobacterium leprae in which susceptibility to the mycobacteria and its clinical manifestations are attributed to the host immune response. Even though leprosy prevalence has decreased dramatically, the high number of new cases indicates active transmission. Owing to its singular features, M. leprae infection is an attractive model for investigating the regulation of human immune responses to pathogen-induced disease. Leprosy is one of the most common causes of nontraumatic peripheral neuropathy worldwide. The proportion of patients with disabilities is affected by the type of leprosy and delay in diagnosis. This article briefly reviews the clinical features as well as the immunopathological mechanisms related to the establishment of the different polar forms of leprosy, the mechanisms related to M. leprae-host cell interactions and prophylaxis and diagnosis of this complex disease. Host genetic factors are summarized and the impact of the development of interventions that prevent, reverse or limit leprosy-related nerve impairments are discussed.

T regulatory cells and plasmocytoid dentritic cells in hansen disease: a new insight into pathogenesis?

Leprosy is characterized by spectrum of histologically different granulomatous skin lesions that reflects the patient's immune response to Mycobacterium leprae. Presence, frequency, and distribution of both CD4+ CD25+ FoxP3+ T regulatory cells (T-regs) and CD123+ plasmacytoid dendritic cells in leprosy have never been investigated. We performed a retrospective immunohistochemical study on 20 cases of leprosy [tuberculoid tuberculoid (TT): 1 patient; borderline tuberculoid (BT): 3 patients; borderline lepromatous (BL): 5 patients; lepromatous lepromatous (LL): 5 patients; borderline borderline in reversal reaction (BB-RR): 1 patient; BT-RR: 2 patients; and erythema nodosum leprosum (ENL): 3 patients]. FoxP3-positive cells were present in 95% of the cases with an average density of 2.9% of the infiltrate. Their distribution was not related to granulomatous structures or special locations. There was no statistical difference of FoxP3 expression between TT, BT, BL, and LL, whereas a statistical significant increment (P = 0.042) was observed in patients affected by reversal leprosy reactions (BT-RR and BB-RR) compared with patients affected by ENL and patients with nonreactional disease forms (BL, LL, BT, TT). CD123 expression was not observed in any of the biopsy specimens evaluated; with the exception of 2 cases of ENL, in which a focal positivity for CD123 was observed. Our results show that plasmacytoid dendritic cells are not involved in the immune response against M. leprae while T-regs are present in leprosy skin lesions. These data raise the question if T-regs have a pathogenetic role in HD as previously demonstrated in Leishmania major and Mycobacterium tuberculosis.

Host and parasite factors affecting the invasion of mononuclear phagocytes by Trypanosoma cruzi

Epimastigotes and trypomastigotes of Trypanosoma cruzi enter mouse and human macrophages by phagocytosis. Organisms are initially found in a parasitophorous vacuole, and fusion with lysosomes promptly ensues. Epimastigotes are rapidly killed and digested in phagolysosomes. Trypomastigotes, however, soon escape the confines of the vacuolar system and reach the cytoplasm, where they replicate. Metacyclic trypomastigotes are quickly taken up by mouse and human macrophages. In contrast, blood-form trypomastigotes are resistant to interiorization by mononuclear phagocytes. This effect can be overcome, without affecting parasite survival, by opsonization of the parasites with immunoglobulin G (IgG)-class antibodies or by removal of trypomastigote surface peptides with trypsin. The major surface glycoprotein (relative molecular mass 90 000) of the mammalian stages of T. cruzi has been implicated in this antiphagocytic effect. This surface glycoprotein seems to have glycosidase activity, and the antiphagocytic effect may be mediated via the removal of sugar residues necessary for parasite internalization by macrophages. This enzyme activity may explain other evasion mechanisms displayed by T. cruzi bloodstream forms. These include antibody-mediated complement lysis and Fc-receptor-mediated phagocytosis. Trypomastigotes are, however, promptly killed in mouse and human macrophages activated by either in vivo infection or in vitro treatment with sensitized, antigen-stimulated, T-cell products. Increased production of reactive oxygen intermediates by activated cells has been implicated as the mechanism of intracellular killing in mononuclear phagocytes. Opsonization by IgG-class antibodies enhances uptake of the parasites but does not affect their fate in normal mononuclear phagocytes. In contrast, it enhances their killing by activated macrophages, suggesting that antibodies may have a major protective role only in the presence of concomitant cell-mediated immunity.

Long-term culture of multibacillary leprosy macrophages isolated from skin lesions: a new model to study Mycobacterium leprae-human cell interaction

BACKGROUND

Leprosy is characterized by a disease spectrum having two polar clinical forms dependent on the presence or not of cell-mediated immunity. In the tuberculoid forms, granuloma-activated macrophages kill Mycobacterium leprae in conjunction with a Th1 response while, in multibacillary (MB) lesions, M. leprae nonactivated macrophages infiltrate the nerves and internal organs together with a Th2 response. The functional properties and activation pathways of macrophages isolated from patients with MB leprosy remain only partially understood.

OBJECTIVES

To establish an ex vivo methodology capable of evaluating the activation pathways, grade and fate of cultured macrophages isolated from MB lesions.

METHODS

Skin biopsies from patients with borderline tuberculoid, bordeline lepromatous and lepromatous leprosy (LL) were characterized by immunohistochemistry and transcriptional analysis. To isolate inflammatory cells, a portion of the samples was submitted to enzymatic digestion. These same cells, maintained in culture for a minimum 7-day period, were characterized morphologically and via flow cytometry at different culture time points. Cytokine [interferon (IFN)-gamma, tumour necrosis factor (TNF)-alpha and interleukin (IL)-10] mRNA levels were quantified by real-time polymerase chain reaction and protein secretion in the culture supernatants was measured by enzyme-linked immunosorbent assay and the nitric oxide levels by Griess reagent.

RESULTS

RNA expression in tuberculoid and MB lesions showed the profile expected of characteristic Th1 and Th2 responses, respectively. The inflammatory cells in all biopsies were successfully isolated. Although the number of cells varied between biopsies, it was highest in LL biopsies. The frequency of isolated CD14+ and CD3+ cells measured by flow cytometry correlated with the percentages of macrophages and lymphocytes in the lesions. Throughout the culture period, CD68+ macrophages showed morphological changes. A progressive increase in cell number and reduction of infected cells were perceptible in the cultures. In contrast to the biopsies, TNF-alpha, IFN-gamma and IL-10 expression in the tuberculoid and MB leprosy cells in 24-h culture and the cytokine levels in the supernatants did not differ significantly. During the culture period, cytokine expression in the MB cells progressively declined, whereas, from days 1 to 7, nitrite levels progressively increased. After day 40, the remaining macrophages were able to ingest fluorescein isothiocyanate-labelled M. leprae. These data need to be confirmed.

CONCLUSIONS

This study confirmed the feasibility of obtaining ex vivo macrophages from leprosy lesions and keeping them in long-term culture. This procedure may open new pathways to studying the interaction between M. leprae and human macrophages, which might, in turn, lead to the development of therapeutic tools capable of overcoming the specific anergy found in patients with MB leprosy.

Interactions between HIV infection and leprosy: a paradox

Early in the HIV epidemic it was feared that the disease would undermine leprosy control, as has occurred with tuberculosis. It was predicted that patients with leprosy and HIV coinfection would have an increased risk of lepromatous disease and a faster clinical evolution, and that the leprosy would be more difficult to treat. None of these concerns have materialised and the interaction between HIV and Mycobacterium leprae seems to be far more subtle than that between HIV and tuberculosis. We review the epidemiological, clinical, and pathological data relating to leprosy/HIV coinfection. The published epidemiological data are limited in quality but show neither an increased HIV prevalence among leprosy cases nor an alteration in clinical spectrum of leprosy among coinfected patients. Some data suggest that immune-mediated reactions that complicate leprosy occur at a higher frequency in coinfected patients. Leprosy has now been reported presenting as immune reconstitution disease among patients commencing highly active antiretroviral treatment. Histopathological observations reveal a normal spectrum of appearances in biopsies of leprosy lesions from coinfected patients, even among those with advanced immunodeficiency. These observations suggest that cell-mediated immune responses to M leprae are preserved at the site of disease despite evidence that these responses are abrogated systemically, by contrast with tuberculosis, in which the host granulomatous response is impaired by HIV coinfection. We speculate that this paradox may relate to differences between the activation state and rates of cell turnover within leprosy and tuberculosis granulomas that differentially affect the susceptibility of the granulomas to HIV. The interactions between leprosy and HIV have been little studied and further research on the clinical, pathological, and management aspects of this coinfection is warranted.

[Immunopathology of leprosy: the complexity of the mechanisms of host immune response to Mycobacterium leprae]

Leprosy, whose etiologic agent Mycobacterium leprae, is an illness of ample clinical and immunopathological spectrum. Its clinical manifestations are correlated with distinct immunologic forms, varying from a vigorous immune response mediated by cells to M. leprae, with Th1 standard in the tuberculoid polar region, to an absence of specific cellular response to antigens of M. leprae in the lepromatous polar region, with predominance of Th2 response and exacerbation of humoral response. It is probable that different polymorphic genes determine susceptibility to M. leprae. Additional studies are necessary to clarify the complex interactions between cytokines and the role of the phenotypic diversity of cells network that contribute to the host defense. The comprehension of such mechanisms will provide new insights for the identification of agonists and/or antagonists for pro- or anti-inflammatory effects, and also will indicate possible situations for its appropriate use in immunologic and/or immunotherapeutic interventions.

Lesional T-cell subset in leprosy and leprosy reaction

BACKGROUND

The T-cell-mediated immune response plays an important role in leprosy. The in situ proportion and pattern of distribution of T-cell subsets in leprosy skin lesions have been studied, but no conclusion could be drawn.

METHODS

We used monoclonal antibodies for T-helper and T-suppressor surface antigen to define the nature of dermal infiltration in 17 cases of nonreactional leprosy and 20 cases of reactional leprosy.

RESULTS

We found T helper admixed with T suppressor in an aggregated pattern in the granulomas of most cases of nonreactional leprosy and in type I reactional leprosy, but a diffuse infiltrate throughout the dermis of type II reactional leprosy. The T-helper/suppressor ratio was 1.68 in tuberculoid and 1.5 in lepromatous cases. The T-helper/ suppressor ratios of borderline tuberculoid (3.11) and type I reactional leprosy (2.54) were not statistically different. The T-helper/suppressor ratio of type II reactional leprosy (5.83) was statistically higher than nonreactional lepromatous cases.

CONCLUSIONS

The alteration of the T-helper/suppressor ratio in our study is mainly due to the reduction of T-suppressor cells in the dermal infiltrates, especially in type II reactional leprosy. Further studies of T-suppressor functions may be important in the pathogenesis of leprosy.

Mycobacterial lymphadenitis associated with the initiation of combination antiretroviral therapy

OBJECTIVE

To characterize the impact of combination antiretroviral therapy on the clinical and laboratory features of mycobacterial lymphadenitis, we conducted a retrospective chart review of HIV-related mycobacterial lymphadenitis at St. Paul's hospital between 1989 and 1997. Among 52 evaluable patients, 12 presented within 12 weeks of initiating combination antiretroviral therapy (group 1, n = 12); the others developed lesions while receiving no antiretrovirals, monotherapy, or a stable combination regimen of >12 weeks duration (group 2, n = 40).

RESULTS

Group 1 patients had higher absolute CD4 lymphocyte counts (median, 150 versus 20 cells/mm3, respectively; p = .001) and hemoglobin levels (median, 113 versus 88 g/L, respectively; p = .002) at the time of mycobacterial diagnosis. Clinical comparison showed that group 1 patients were more likely to develop a draining sinus (50% versus 0%; p < .001), but less often to have weight loss (17% versus 74%; p < .0001) or disease which was disseminated (25% versus 70%; p = .04) or caused by Mycobacterium tuberculosis (0% versus 33%; p = .04).

CONCLUSIONS

Mycobacterial lymphadenitis developing within 12 weeks of initiating combination antiretroviral therapy is often localized Mycobacterium avium complex disease, associated with a relatively high CD4 count. The clinical course is often complicated by the development of a draining sinus. The close temporal association suggests that such treatment may unmask subclinical infection by enhancing the immune response to mycobacterial antigens.

CD1 Expression by Dendritic Cells in Human Leprosy Lesions: Correlation with Effective Host Immunity

A potential role for the CD1 family of lipid Ag-presenting molecules in antimicrobial immunity in vivo was investigated in human leprosy skin lesions. Strong induction of three CD1 proteins (CD1a, -b, and -c) was observed in dermal granulomas in biopsy samples of involved skin from patients with the tuberculoid form of leprosy or with reversal reactions, which represent clinical patterns of disease associated with active cellular immunity to Mycobacterium leprae. In contrast, lesions from patients with the lepromatous form of the disease who lack effective cell-mediated immunity to the pathogen did not show induction of CD1 proteins. Thus, expression of CD1 correlated directly with effective immunity to M. leprae, as assessed by the clinical course of infection. CD1a, -b, and -c could be induced to similar levels on monocytes from the blood of either tuberculoid or lepromatous leprosy patients. This suggested that the absence of expression in lepromatous lesions was most likely due to local factors at the site of infection as opposed to a primary defect of the CD1 system itself. The majority of cells expressing CD1 in leprosy lesions were identified as a population of CD83+ dendritic cells. Initial in vitro studies of the Ag-presenting function of CD1+CD83+ monocyte-derived dendritic cells showed that such cells were highly efficient APCs for CD1-restricted T cells. These results indicate that the CD1 system can be up-regulated in human infectious diseases in vivo, and may play a role in augmenting host defense against microbial pathogens.

Multibacillary leprosy: lesions with macrophages positive for S100 protein and dendritic cells positive for Factor 13a

In the defense against Mycobacterium leprae, macrophages play an essential part in the mechanism of bacterial lysis but require the presence of cytokines such as interleukin 2 and gamma interferon from lymphocytes in order to effectively kill the organisms in any number. While there have been many studies of the lymphocytes in lesions of leprosy, less attention has been given to the immunohistochemical characterization of the macrophage populations. In this study, the cutaneous lesions of 69 patients with leprosy (42 lepromatous, 5 mid-borderline, and 22 tuberculoid) were evaluated by immunohistochemistry for the expression of S100 protein, CD1a, CD68, muramidase, HLA-DR, and Factor 13a. The macrophages from lesions of polar, subpolar, and borderline lepromatous leprosy patients expressed S100 protein intensely and constantly. In contrast, the lesions of polar and subpolar tuberculoid leprosy had very few cells that were immunoreactive for S100 protein ('S100+') in the granulomas in the dermis. The macrophages in all lesions were reactive for CD68 and muramidase. In paraffin sections, macrophages of lepromatous lesions failed to stain for HLA-DR, whereas in tuberculoid lesions, they were strongly positive for HLA-DR. Three patients with histoid leprosy (relapse lesions) had lesions that were strongly positive for Factor 13a and were negative for S100 protein ('S100-'). Given the possible chemotactic and migration inhibition effects of the calcium-binding proteins of the S100 family, these data suggest a possibly important role for S100 protein in the accumulation of macrophages in lepromatous leprosy, and also reveal infection of Factor 13a + dermal dendritic cells in histoid leprosy.

Changes in expression of signal transduction proteins in T lymphocytes of patients with leprosy

Advanced stages of mycobacterial diseases such as leprosy and tuberculosis are characterized by a loss of T-cell function. The basis of this T-cell dysfunction is not well understood. The present report demonstrates major alterations in the expression of signal transduction molecules in T cells of leprosy patients. These alterations were most frequently observed in lepromatous leprosy (LL) patients. Of 29 LL patients, 69% had decreased T-cell receptor zeta-chain expression, 48% had decreased p56(lck) tyrosine kinase, and 63% had a loss of nuclear transcription factor NF-kappaB p65. An electrophoretic mobility shift assay with the gamma interferon core promoter region revealed a loss of the Th1 DNA-binding pattern in LL patients. In contrast, tuberculoid leprosy patients had only minor signal transduction alterations. These novel findings might improve our understanding of the T-cell dysfunction observed in leprosy and other infectious diseases and consequently might lead to better immunologic evaluation of patients.

Immunopathological mechanisms in bacterial-host interactions

The ability of bacteria to cause immunopathological damage in the host may take a variety of forms. These pathways may be conveniently grouped under three major headings: (1) organisms that can cause damage via shared antigenic determinants between host and bacterium; (2) those organisms that suppress the host’s response; and (3) organisms that release substances with specific biological properties or have receptors for specific tissue sites. The group A streptococcus is among the most versatile of these bacteria because it appears that it may use all three pathways in various streptococcal-related disease states. In rheumatic fever and chorea it appears that cross-reactive antigens play a major role in inducing immunopathological damage in that there is both a heightened humoral and cellular reaction by the host to these cross-reactive determinants. Recent evidence also indicates that rheumatic fever individuals express certain B cell antigens that may be associated with susceptibility to the disease. In the other complications of streptococcal infections, namely poststreptococcal glomerulonephritis, the bacterium uses both suppression of the host’s immune response and the excretion of a particular protein common to all nephritis-associated strains to achieve its immunopathological damage. In this context, other examples of bacterial-host interactions will be discussed as evidence for the common pathways used by microbes to cause immunopathological damage in the host.

Phenotypic characterisation of intestinal lymphocytes in ovine paratuberculosis by immunohistochemistry

Characterisation of the T-cell subsets in intestinal lesions in sheep with paratuberculosis may contribute to our understanding of the pathogenesis of this disease. To determine the phenotype and distribution of lymphocytes in the normal sheep intestinal mucosa and in Mycobacterium avium subspecies paratuberculosis infected sheep, immunohistochemistry was performed on 12 normal sheep and 18 naturally infected, clinically diseased sheep of which 12 showed lepromatous and six tuberculoid forms of the disease. Immunoperoxidase staining was carried out on frozen sections of ileum using monoclonal antibodies against ovine CD4, CD8, and gamma delta T-cell receptor (TCR) markers. In all three sample groups, cells appeared to be non-randomly distributed throughout the lamina propria. Higher densities of lymphocytes were present in villus than in crypt areas. CD8+ cells were located principally around the epithelial basement membrane, whereas CD4+ cells were localised towards the central villus area of the lamina propria. Lymphocytes bearing the gamma delta T-cell receptor were more widely distributed, both in epithelial and lamina propria compartments. Ileum with tuberculoid lesions had higher densities of CD4 and gamma delta T-cell subsets while lepromatous lesions had lower densities of CD4 and CD8 cells compared with normal tissues. The median relative percentage of CD4+ cells was increased and that of CD8+ cells decreased in tuberculoid cases, with a corresponding increase in the CD4:CD8 ratio, while the relative percentage of gamma delta + cells was increased in lepromatous cases.

Cellular immune response to Mycobacterium leprae infection in human immunodeficiency virus-infected individuals

The immune responses to Mycobacterium leprae and other mycobacterial antigens were studied in 11 leprosy patients with concurrent human immunodeficiency virus type 1 (HIV-1) infection. Three patients manifested borderline lepromatous leprosy, and eight patients had borderline tuberculoid (BT) leprosy. Despite the low CD4+ T-cell count in the peripheral blood, no histologic or phenotypic change in the cellular infiltrate in either the lepromatous or tuberculoid lesions was observed when compared with HIV-1-negative patients. Lepromatous lesions contained heavily parasitized macrophages and few CD8+ T cells. Lesions from the patients with BT leprosy showed extensive CD4+ T-cell infiltration despite a significant reduction in CD4+ T-cell counts in the peripheral blood. No acid-fast bacilli were detected in the tuberculoid lesions. HIV-1 infection did not alter the lack of response in lepromatous leprosy to M. leprae antigens either in vitro or in vivo. In contrast, the skin test response to M. leprae antigens as well as the in vitro lymphoproliferative responses to mycobacterial antigens that are usually seen in patients with tuberculoid leprosy were abrogated in the BT HIV-1+ patients. However, production of gamma interferon in response to the same stimuli was preserved in most of the patients. Analysis of cytokine gene expression showed activation of additional cytokine genes in the unstimulated peripheral blood cells of patients with both leprosy and HIV-1 infections as compared with cells from patients with leprosy alone. These results suggest that granuloma formation in leprosy can be independent of the impaired CD4+ T-cell response of the HIV-1 infection. Furthermore, in HIV-1+ individuals with M. leprae infection, activation of cytokine genes is observed even when the circulating CD4+ T-cell count is significantly reduced.

Antigen-presenting cells in human cutaneous leishmaniasis due to Leishmania major

In this study biopsies from skin lesions and draining lymph nodes of patients suffering from cutaneous leishmaniasis caused by Leishmania major were examined by immunohistochemistry, and by light and electron microscopy to identify the types of antigen-presenting cells (APC) and their location. APC, identified morphologically and by their expression of specific cell markers, included Langerhans cells, macrophages, follicular dendritic cells, and interdigitating reticulum cells of the paracortex of lymph nodes. These cells expressed MHC class II antigens and contained Leishmania antigen. Since some keratinocytes and endothelial cells also showed these characteristics, they may also act as APC. By examining tissue samples from skin lesions and draining lymph nodes it was possible to follow the probable route of trafficking of various inflammatory cells between the skin lesion and lymph nodes. Leishmania antigen containing Langerhans cells were found in the epidermis, dermis and the regional lymph nodes. We believe these cells translocate from the epidermis to the dermis, where they take up antigen and migrate to the paracortex of the regional lymph nodes. There they are intimately associated with cells of the paracortex, and could be involved in the generation of Leishmania-specific T memory cells. LFA-1-positive T cells of the CD45RO phenotype were found in the skin lesion. Venular endothelium in the skin lesions expressed intercellular adhesion molecule-1 (ICAM-1), which is the ligand for LFA-1. The migration of lymphocytes from the vascular lumen to the site of inflammation is possibly a result of the interaction of these two adhesion molecules.

Mycobacterium leprae DNA content, cellular and cytokine patterns in skin lesions of leprosy patients undergoing multidrug therapy (MDT)

Skin biopsies from untreated and MDT-treated patients were examined for infiltrating cells and cells producing the cytokines TNF-alpha, IFN-gamma, and IL-1 beta using immunohistochemistry. Biopsy specimens from untreated tuberculoid leprosy patients were characterized by the presence of cells producing TNF-alpha, IFN-gamma, and IL-1 beta and of subepidermal Langerhans cells. These cells were rarely found or completely absent in biopsies of untreated lepromatous leprosy patients, but tended to increase under MDT. In a short-term therapy trial for three months with brodimoprim, dapsone, and rifampicin, 12 patients were monitored by follow-up biopsies. Semiquantitative PCR for mycobacterial DNA revealed two groups of patients: one group in which mycobacterial DNA in follow-up biopsies remained constant and a second group in which a decrease of mycobacterial DNA during therapy was noted. Immunophenotyping in these follow-up biopsies revealed that in the latter group IFN-gamma-positive cells and Langerhans cells were present and gamma delta T cell receptor-positive cells tended to decrease during therapy. In contrast, in patients whose mycobacterial DNA did not change during therapy, these phenotypical manifestations were not observed. We therefore, conclude that assessment of mycobacterial DNA in combination with phenotyping of infiltrating cells and determination of cytokine patterns may be useful tools in establishing criteria for the effectiveness and duration of MDT in patients with leprosy.

In situ characterization of lymphocytic immunophenotypes and interleukin-2 receptors in cutaneous tuberculosis and leprosy--a comparative evaluation

The granulomas of lupus vulgaris (LV) were characterized by preponderance of CD4+ lymphocytes and a raised CD4+/CD8+ ratio. In contrast, in scrofuloderma (SF) the CD8+ T-lymphocyte subpopulation predominated and the CD4+/CD8+ ratio was significantly decreased. A higher percentage of lymphocytes expressed interleukin-2 receptor (IL-2R) in LV as compared with SF, indicating an activated cellular immune response in the former. Immunophenotypic changes in tuberculosis verrucosa cutis (TBVC) were intermediate between LV and SF. CD4+ lymphocytes were the main infiltrating T-cell type in borderline tuberculoid leprosy (BT), while CD8+ lymphocytes predominated in the granuloma of lepromatous lepromatous (LL). The CD4+/CD8+ ratio and percentage of lymphocytes expressing IL-2R was significantly higher in BT as compared with LL. These immunophenotypic findings suggest that in both cutaneous tuberculosis and leprosy there is a continuous spectrum with regard to cell-mediated immunity depending on the clinical presentation.

Th1-Th2 paradigm: insights from leprosy

The mechanism by which T cells and cytokines regulate immune processes in skin can be investigated by studying patients with leprosy. The disease, caused by the obligate intracellular bacterium Mycobacterium leprae, forms a spectrum. At one pole, patients with tuberculoid leprosy are able to restrict the growth of the pathogen and their skin lesions are characterized by a predominance of CD4+ T cells and type 1 cytokines including interleukin 2 and interferon gamma. At the opposite pole, patients with lepromatous leprosy are unable to contain the infection and their skin lesions are characterized by a predominance of CD8+ T cells and type 2 cytokines including interleukins 4 and 10. A key determinant of the T-cell cytokine response may be interleukin 12, which selectively favors expansion of CD4+ T cells producing interferon gamma. By understanding the factors that regulate T-cell and cytokine responses in leprosy, it should be possible to devise specific immunologic interventions in diseases of skin.

Lung diseases in the tropics. Part 1: Tropical granulomatous disorders of the lung: diagnosis and management

International travel, student and cultural exchanges and changing immigration patterns are insidiously transforming the face of medicine in the United States, Europe and other developed countries. It is essential that the practising clinician be aware of the increasing prevalence of various new and exotic tropical lung diseases. The definitive diagnosis of the pulmonary granulomas that constitute the bulk of lung disorders in the tropics is important since the treatment varies significantly. At the same time, recent developments in molecular biology, immunology and biochemistry have increased the diagnostic accuracy and therapeutic effectiveness related to tropical granulomatous disorders. Clinicians in the developing countries can now supplement their clinical acumen with rapid advances in immunology and histopathology enabling them to grasp the fundamental mechanisms of granuloma formation. Mycobacterial, fungal, parasitic, spirochetal and other infections must be differentiated from a variety of non-infectious granulomas including sarcoidosis, hypersensitivity pneumonitis, drug reaction and generalized vasculitis since therapy is vastly different. The treatment, if inappropriate, may not only be worthless but, in many cases, extremely harmful and even fatal.

The mycobacterial secreted antigen 85 complex possesses epitopes that are differentially expressed in human leprosy lesions and Mycobacterium leprae-infected armadillo tissues

The granulomatous skin lesions in leprosy are thought to be initiated by the immune response to certain antigens of the causative agent, Mycobacterium leprae. The antigen 85 complex is one of the major targets in the immune response to M. leprae infection. In the present study, a panel of previously characterized monoclonal antibodies (MAbs) (3A8, Rb2, A4g4, A2h11, Pe12, and A3c12) reacting with different epitopes of the 85 complex proteins of Mycobacterium tuberculosis and M. leprae was employed in a comparative immunohistological analysis to demonstrate the in situ expression of 85 complex antigenic epitopes in leprosy lesions across the clinical spectrum and in M. leprae-infected armadillo liver tissues. These MAbs showed a heterogeneous staining pattern in a given leprosy lesion. In highly bacilliferous borderline and lepromatous leprosy lesions, MAbs Rb2, A4g4, A2h11, and Pe12 stained clear rod-shaped M. leprae bacilli within macrophages, and the degree of staining correlated with the bacillary index of the lesion. On the other hand, MAbs 3A8 and A3c12 staining was mostly seen as a diffuse staining pattern within interstitial spaces and on the membranes of the infiltrated cells but not the bacilli. In paucibacillary borderline and tuberculoid leprosy lesions, only 3A8, Rb2, and A3c12 showed distinct staining in association with infiltrates in the granuloma. None of these MAbs showed any detectable reaction with control nonleprosy skin lesions, while MAb A3c12 positively stained the granulomas of both leprosy and control specimens. In situ reactivity of these MAbs with M. leprae-infected armadillo liver tissues also showed a heterogeneous staining pattern. Interestingly, a clear difference in expression of these epitopes was observed between armadillo tissues and human leprosy lesions. By immunogold ultracytochemistry, we further showed the differential localization of these MAb-reactive epitopes on the cell surface, in the cytosol, and at the vicinity of M. leprae within Kupffer cells of armadillo liver tissues. Our results indicate that these antigenic epitopes of the antigen 85 complex are differentially expressed in leprosy lesions and infected armadillo tissues and that they could be target determinants in the immunopathological responses during M. leprae infection.

Two sisters with leprosy

Leprosy is a rare entity in Japan, but remains quite common in developing countries. We report two sisters with leprosy from Brazil but currently working in Japan who presented to our clinic. The younger sister was infected with the BB type with HLA-A2, A24, B51, Bw52, DR2, DRw8, DRw52, DQw1, and DQw3. The elder sister had the TT type with HLA-A2, A31, B51, Cw3, DRw6, DRw8, DRw52, DQw1, and DQw3. Immunohistochemical findings revealed that CD4+, 4B4+ helper/inducer T-cells were dominant in the granulomas of both cases. Bacilli were not detectable in the biopsy specimens. However, Mycobacterium leprae-specific DNA fragments were found in their peripheral blood and biopsy specimens by polymerase chain reaction.

Isolated granulomatous angiitis of the spinal cord

We describe a 31-year-old diabetic man, with granulomatous angiitis confined to the spinal cord, who developed rapidly progressive spastic paraplegia, clinically interpreted as being secondary to a spinal cord infarct. At the time of autopsy, vasculitis was limited to the spinal cord, without involvement of cerebral vessels. The inflammatory cells were predominantly CD4+ T lymphocytes, with few CD8+ T and B lymphocytes. The phenotypical composition of the inflammatory infiltrate is similar to that described in other granulomatous disorders such as sarcoidosis and tuberculin reaction.

T-cell-mediated cytotoxicity against Mycobacterium antigen-pulsed autologous macrophages in leprosy patients

The involvement of CD4+ T lymphocytes in the defense mechanisms against intracellular pathogens is widely recognized. Little information is available on the generation and specificity of the cytotoxic cells that eliminate human monocytes/macrophages infected with mycobacteria. In this work, we tested whether mononuclear cells from leprosy patients could generate cytotoxic T-cell activity against autologous macrophages pulsed with Mycobacterium leprae or purified protein derivative (PPD) in a 4-h 51Cr release assay. Peripheral blood mononuclear cells from normal Mycobacterium bovis BCG-immunized controls or from leprosy patients stimulated with antigen for 7 days were used as effector cells. Paucibacillary (PB) patients and normal controls yielded more active effector cells in this system than multibacillary (MB) patients. MB patients were able to develop cytotoxicity against M. leprae, BCG, or PPD, in contrast with the immunological anergy widely described. We did not find cytotoxicity against unpulsed macrophages. Cross-reactivity was observed between PPD, BCG, and M. leprae. Only antigen-pulsed autologous macrophages were suitable as target cells. M. leprae-induced cytotoxic cells were found in both CD4+ CD8- and CD4- CD8+ T-cell subsets, whereas CD4+ cells were the main component of PPD-induced cytotoxicity. In MB patients, BCG-induced cytotoxic cells were better killers of M. leprae-pulsed macrophages than cells induced by M. leprae. This is an interesting finding in view of the ongoing vaccination trials. The involvement of CD4- or CD8-mediated cytotoxicity may be important in the balance between protection and tissue or nerve damage.

Association of the mycobacterial 30-kDa region proteins with the cutaneous infiltrates of leprosy lesions. Evidence for the involvement of the major mycobacterial secreted proteins in the local immune response of leprosy

The granulomatous skin lesions of human leprosy are known to be due to the cutaneous immune reaction to various mycobacterial antigens. In the present study, by immunohistochemical analysis using a previously characterized monoclonal antibody (MoAb) 3A8 we have demonstrated a selective expression of the 3A8 epitope of mycobacterial 30-kDa proteins, the major secreted proteins of mycobacteria, in various forms of leprosy lesions across the clinical spectrum. The localization of MoAb 3A8 staining is confined to the areas of cellular infiltrates of the lesions. In tuberculoid lesions the intense 3A8 staining was seen mostly in association with the membrane of the dermal cellular infiltrates whereas in highly bacilliferous lepromatous lesions the staining seems to be diffused with granular appearance but not in the form of bacteria. In patients with reversal reaction the staining was specifically extended to cells infiltrating the epidermis. MoAb 3A8 did not show any reactivity with inflammatory skin lesions of patients other than those with leprosy. Since the 3A8 epitope of 30-kDa proteins has been shown to be present in all cellular compartments of the mycobacteria and in the actively secreted BCG 85 antigen complex, MoAb 3A8 reactive protein(s) in leprosy lesions may be derived either from degraded somatic mycobacterial products or from antigens actively secreted by live bacilli. The latter could be true in the cases of untreated lepromatous lesions with high bacterial load since live M. leprae has also been considered to secrete corresponding 30-kDa proteins similar to other closely related mycobacteria. By double immunoenzyme staining we clearly demonstrate the expression of 3A8 epitope on CD68+ macrophages in the granulomas of tuberculoid leprosy, whereas in highly bacilliferous lepromatous lesions most of the double staining was seen in a diffuse pattern within the interstitial space of the cellular infiltrate as well as in the cytoplasm of CD68+ macrophages. In lesions from reversal reaction the 3A8 epitope is more strongly expressed on CDla+ dendritic Langerhans cells (LC) both in the epidermis and in the dermis as compared with other types of leprosy. This provides evidence for the involvement of LC in handling of mycobacterial antigenic epitopes in leprosy lesions. Further, immunoenzyme double staining revealed that the expression of this mycobacterial 3A8 epitope on antigen presenting cells such as CD68+ macrophages and CDla+ LC is present in juxtaposition with CD3+ T cells including the alpha beta and gamma delta receptor-bearing T cells in the granuloma.(ABSTRACT TRUNCATED AT 400 WORDS)

Hypotheses on the pathogenesis and natural history of Helicobacter pylori-induced inflammation

Although Helicobacter pylori is now recognized as playing an etiologic role in chronic gastritis and peptic ulcer disease, information on the pathogenesis and natural history of infection is limited. A model is proposed in which luminal H. pylori secrete substances that mediate inflammation that is beneficial to the organism but ultimately deleterious for the host; in addition to tissue damage, inflammation also affects gastric secretory function. In this model, the host may attempt to suppress the inflammatory response, and the adequacy of this postulated down-regulation determines pathological and clinical outcome. The effects of the inflammatory process on gastrin-hydrochloric acid homeostasis may be of critical importance in the pathogenesis of peptic ulcer disease. Because the long-term consequences of H. pylori colonization reflect the continued presence of the organism in the host over years or decades, it may be useful to consider this as a "slow" bacterial infection.

Defining protective responses to pathogens: cytokine profiles in leprosy lesions

The immunological mechanisms required to engender resistance have been defined in few infectious diseases of man, and the role of specific cytokines is unclear. Leprosy presents clinically as a spectrum in which resistance correlates with cell-mediated immunity to the pathogen. To assess in situ cytokine patterns, messenger RNA extracted from leprosy skin biopsy specimens was amplified by the polymerase chain reaction with 14 cytokine-specific primers. In lesions of the resistant form of the disease, messenger RNAs coding for interleukin-2 and interferon-gamma were most evident. In contrast, messenger RNAs for interleukin-4, interleukin-5, and interleukin-10 predominated in the multibacillary form. Thus, resistance and susceptibility were correlated with distinct patterns of cytokine production.

Differing lymphokine profiles of functional subsets of human CD4 and CD8 T cell clones

Functional subsets of human T cells were delineated by analyzing patterns of lymphokines produced by clones from individuals with leprosy and by T cell clones of known function. CD4 clones from individuals with strong cell-mediated immunity produced predominantly interferon-gamma, whereas those clones that enhanced antibody formation produced interleukin-4. CD8 cytotoxic T cells secreted interferon-gamma. Interleukin-4 was produced by CD8 T suppressor clones from immunologically unresponsive individuals with leprosy and was found to be necessary for suppression in vitro. Both the classic reciprocal relation between antibody formation and cell-mediated immunity and resistance or susceptibility to certain infections may be explained by T cell subsets differing in patterns of lymphokine production.