Leprosy mimicking autoimmune diseases: a case series.

OBJECTIVES: Leprosy is a chronic granulomatous disease caused by Mycobacterium leprae. Less frequently, there is involvement of the musculoskeletal system, and occurrence of systemic manifestation with non-specific symptoms such as fever, fatigue and myalgia. Therefore, leprosy can often mimic autoimmune diseases such as arthritis, vasculitis, or collagenosis and be mis-diagnosed. METHODS: This study describes a series of cases of leprosy mimicking autoimmune diseases in patients treated in the Rheumatology Department of our centre in the period 2019 to 2023. All patients were investigated regarding leprosy criteria and had clinical evaluation, serum markers, and histopathological analyses recorded. The diagnosis of leprosy was confirmed using skin biopsy followed by testing for acid-fast bacillus (AFB) or smear microscopy. RESULTS: Six patients who were initially investigated for autoimmune diseases were identified as diagnosed as leprosy cases, fulfilling both clinical and histopathologic criteria, two of whom presented with symptoms of polyarthritis with an inflammatory characteristic, two diffuse erythematous-violaceous lesions, three recurrent fever, three arthralgia, and one Raynaud's phenomenon, which are all characteristics present most frequently in rheumatologic diseases. CONCLUSIONS: We must consider the bacillary infection as a differential diagnosis of autoimmune diseases. Histopathological analysis is an important tool and the gold standard for diagnostic confirmation.

JAK-STAT inhibitors in Immune mediated diseases: An Overview.

For any biological response, transmission of extracellular signals to the nucleus is required for DNA transcription and gene expression. In that respect, cytokines/chemokines are well-known inflammatory agents which play a critical role in signalling pathways by activating the Janus kinase-signal transducers and activators of transcription (JAK-STAT) signalling proteins (Janus kinase-signal transducers and activators of transcription) which are a group of intracellular kinase molecules. Cytokines are a category of small proteins (∼5-25 kDa) that play a major role in cell signalling and are major drivers of an autoimmune response. Here we will discuss the role of Janus kinase-signal transducers and activators of transcription kinase cascades in the inflammatory-proliferative cascades of autoimmune disease and about the recent progress in the development of oral synthetic Janus kinase inhibitors (JAKi) and their therapeutic efficacies in dermatologic and systemic autoimmune diseases. Therapeutic efficacy of Janus kinase inhibitors is now well established in the treatment of array of autoimmune and inflammatory disease: spondylarthritis with a special focus on psoriatic arthritis (PsA) and its dermatologic manifestations (psoriasis) and ankylosing spondylitis (AS), atopic dermatitis (AD), alopecia areata (AA), rheumatoid arthritis (RA) and inflammatory bowel disease (IBD). In addition to the first-generation Janus kinase inhibitors several new-generation Janus kinase inhibitors are currently being evaluated. It is expected that these Janus kinase inhibitors likely have higher potency and less adverse effects as compared to their predecessors. Here we have discussed: (1) the functional significance of the Janus kinase-signal transducers and activators of transcription kinase cascades in the inflammatory-proliferative processes of autoimmune diseases and its cellular/molecular mechanisms and (2) progress in the development of oral synthetic Janus kinase inhibitors and their therapeutic efficacies in several systemic and cutaneous autoimmune diseases.

JAK inhibitor: Introduction.

The Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway is a key regulatory signaling system for cellular proliferation, differentiation, and apoptosis. In addition, JAK signaling pathway plays critical roles in orchestrating immune response through its interactions with the cytokine receptors and the transcriptions factors. Several key cytokines use JAK-STAT signaling proteins to transduce intra-cellular signals which are involved in the pathogenesis of autoimmune and inflammatory diseases such as in psoriatic disease (psoriasis, psoriatic arthritis), atopic dermatitis, alopecia areata, vitiligo, rheumatoid arthritis, ankylosing spondylitis, lupus erythematosus, Sjogren's syndrome, and other autoimmune diseases. In recent years, understandings of the molecular mechanisms of JAK-STAT pathway in the inflammatory proliferative cascades of autoimmune diseases has led to the development of JAK inhibitors and has opened a new dimension for the treatment of systemic and cutaneous inflammatory diseases. In this symposium we have provided a broad perspective on the use of Janus kinase inhibitors in cutaneous autoimmune diseases.

Outcome of COVID-19 in patients with autoimmune bullous diseases.

Background Data on outcomes of Coronavirus disease 2019 (COVID-19) infection in autoimmune bullous diseases (AIBDs) patients is scarce. Materials and methods This single-centre survey-based-observational study included patients registered in the AIBD clinic of the Postgraduate Institute of Medical Education and Research, Chandigarh, India. All registered patients were contacted over telephone between June and October 2021. A survey was conducted after obtaining informed consent. Results Among 1389 registered patients, 409 completed the survey. Two hundred and twenty-two (55.3%) patients were females and 187 (45.7%) were males. The mean age was 48.52 ± 14.98 years. Active disease was reported by 34% patients. The frequency of COVID-19 infection in responders was 12.2% (50/409), with a case-fatality ratio of 18% (9/50). Rituximab infusion after the onset of pandemic significantly increased the risk of COVID-19 infection. Active AIBD and concomitant comorbidities were significantly associated with COVID-19 related death. Limitation Relative risk of COVID-19 infection and complications among AIBD patients could not be estimated due to lack of control group. The incidence of COVID-19 in AIBD could not be determined due to lack of denominator (source population) data. Other limitations include telephonic nature of the survey and lack of COVID-19 strain identification. Conclusion Use of rituximab is associated with higher probability of COVID-19 infection, while advanced age, active disease and presence of comorbidities may increase the risk of COVID-19 mortality in AIBD patients.

Long-term presence of autoantibodies in plasma of cured leprosy patients.

Autoantibodies have been detected in leprosy patients, indicating that infection with M. leprae may lead to autoimmune disorders. However, whether autoimmune response last until patients are cured is unknown. Knowing the autoimmune response in cured leprosy patients is essential to identify whether symptoms are caused by leprosy itself or by other immune-related diseases. This knowledge is essential for the ongoing health management in cured leprosy patients where autoimmune disorders still exist. In our study, we selected six autoantibodies, including anticardiolipin antibody of IgG (ACA), anti-nuclear antibody (ANA), extractable nuclear antigen antibody (ENA), anti-streptolysin O (ASO), anti-double stranded DNA antibody (dsDNA), and rheumatoid factor (RF), that had been reported in leprosy patients as typical autoantibodies. We tested the six typical autoantibodies combined with LACC1, which encodes a protein associated with autoimmune disease such as Crohn's disease and is also the susceptible gene conferring leprosy risk, in cured leprosy patients through ELISA to assess the cured patient's immune status. We observed high positive rates of autoantibodies in cured leprosy patients, and the average plasma levels of five (ACA, ANA, ENA, ASO, and RF) out of the six autoantibodies were significantly higher in cured leprosy patients than in controls. The positive detection of autoantibodies is independent of the recovery period. Moreover, the level of these autoantibodies showed a strong positive correlation with the level of LACC1 in both controls and cured patients. This study showed that there is long-term autoimmunological activation in leprosy patients, even after decades of recovery. Autoimmune responses may influence the development and prognosis of leprosy. Special care should be given to posttreatment or cured leprosy patients regarding long-term autoimmunological activation.

Bullous pemphigoid in India: Review of cases registered in an autoimmune bullous disease clinic.

Background Information on bullous pemphigoid in an Indian context is scarce. Aim To report clinico-demographic profile, associated comorbidities and prescription pattern of bullous pemphigoid patients in India. Methods This was a retrospective study, where past records of all bullous pemphigoid patients diagnosed and treated between November 2013 and October 2019 were accessed and analysed. Patients having a compatible clinical presentation with either histopathological and/or direct immunofluorescence evidence of bullous pemphigoid were included. Results There were 96 bullous pemphigoid patients, with a male: female ratio of 1.6:1. The mean age at diagnosis was 62.5 ± 2.2 years, with mean duration of illness 27.5 ± 4.5 months before presentation. Comorbidities were present in 80 (83%) patients, with type 2 diabetes mellitus (38.5%), hypertension (36.4%) and neurological illness (16.7%) being the commonest ones. Clinically, blisters were the predominant presentation in 81 (84.4%) patients. The majority (87.5%) of patients showed a predominant eosinophilic infiltrate on histopathology. Direct immunofluorescence revealed immunoglobulin G deposits with complement C3 in 77 (80.2%) cases. The majority of patients (77.1%) were treated with oral prednisolone, either alone (11.5%) or in combination (65.6%) with other topical and systemic agents. Topical steroids were used in 29.1%, azathioprine in 28%, dapsone in 16.7% and omalizumab in 6.2% of patients. Limitations The study is retrospective. Immunofluorescence on salt split skin, direct immunofluorescence serration pattern analysis, and immunoblotting were not performed. Hence, there is a possibility that a few included cases were suffering from other subepidermal autoimmune bullous diseases like epidermolysis bullosa acquisita or anti-p200 pemphigoid. Conclusion Bullous pemphigoid patients in this study had a younger age of onset and showed male preponderance. Comorbidities like type 2 diabetes, hypertension and neurological disorders were frequent. Cutaneous blisters were the most frequent clinical presentation. Systemic corticosteroids comprised the mainstay of therapy.

Survival and prognostic factors in bullous pemphigoid: A retrospective cohort study.

Background Bullous pemphigoid is the most common subepidermal autoimmune blistering disease. Till now, the reported prognostic factors in bullous pemphigoid vary considerably. Aims The purpose of this study was to determine the overall survival rate and prognostic factors in bullous pemphigoid. Methods We conducted a retrospective cohort study on newly diagnosed bullous pemphigoid patients between July 2001 and November 2019 in a referral unit for autoimmune blistering skin diseases in Romania. Results One hundred forty-eight patients were included in the study. The Kaplan-Meier overall survival rates at 1, 3, 5 and 10 years were respectively 74.2% (95% confidence interval, 67.5-81.6%), 53.4% (45.7-62.2%), 43.6% (35.9-53%) and 31.3% (23.5-41.7%). The median follow-up among survivors was 48 months (interquartile range: 11-150). Ninety (60.8%) patients died during the follow-up period; of them, 38 (42.2%) had active disease at the time of death. Advanced age, neurological diseases, valvular heart disease, malignancies, use of statins, skin infections and extensive cutaneous involvement were linked to poorer outcomes, while the use of topical corticosteroids was associated with increased overall survival. Limitations This study lacks a control cohort to validate the obtained results. It was conducted in a retrospective manner in a single centre. In addition, indirect immunofluorescence microscopy was not performed in all patients. Conclusion Beyond ageing and neurological comorbidities, the prognosis of bullous pemphigoid patients was significantly influenced by the presence of skin infections, valvular heart disease, use of statins and extensive cutaneous involvement. Topical corticosteroid treatment was associated with increased survival in these patients.

Biologics in autoimmune bullous diseases: Current scenario.

Autoimmune bullous diseases can be intraepidermal (pemphigus group of disorders) or subepidermal (pemphigoid group of disorders). The treatment of these disorders chiefly comprises corticosteroids and immunosuppressant adjuvants like azathioprine and mycophenolate mofetil. Autoantibodies are the main mediators of these diseases. Rituximab, a chimeric anti-CD20 monoclonal antibody targeting B-cells, has emerged as an excellent treatment option for refractory pemphigus vulgaris in the last decade. Since then, many new biologics have been proposed/explored for managing autoimmune bullous diseases. These hold potential for greater efficacy and lesser adverse effects than conventional immunosuppressants. In this review, we discuss the role of various biologics in the treatment of autoimmune bullous diseases, followed by a brief discussion on the drawbacks to their use and new developments in this area.

Indications for Rituximab Use in an Integrated Health Care Delivery System.

BACKGROUND: Rituximab is a top-selling biologic that was first approved by the FDA in 1997 for a non-Hodgkin lymphoma orphan indication. It has since been approved for additional orphan indications, with rheumatoid arthritis as the only FDA-approved, nonorphan indication. Evidence suggests that rituximab is frequently used off-label, but information on its use over time and indications for use in the United States is limited. OBJECTIVE: To assess incident rituximab use over time in an integrated health care delivery system. METHODS: This was a cross-sectional, retrospective study. Data were collected from administrative databases and manual chart reviews. Patients who received their first rituximab infusion between October 1, 2009, and December 31, 2017, and who were not a part of a clinical trial were included. Indication for use (FDA-approved orphan/nonorphan, off-label) was determined. Proportions of use were assessed over time. Multivariable logistic regression modeling was performed to assess factors associated with receiving rituximab for an FDA-approved indication. RESULTS: A total of 1,674 patients were included. The majority (66.4%) of patients had an FDA-approved indication, with lymphoma being the most common approved indication (66.4%). The most common indication for off-label use was neurologic conditions (72.7%), predominantly demyelinating diseases. Off-label indication use increased from 1.2% in 2009 to 55.6% in 2017. Factors associated with rituximab use for an FDA-approved indication included increased age (adjusted odds ratio [AOR] = 1.05, 95% CI = 1.04-1.07) and increased burden of chronic disease (chronic disease score: AOR = 1.07, 95% CI = 1.02-1.12; Charlson Comorbidity Index score: AOR = 3.52, 95% CI = 3.03-4.10). CONCLUSIONS: Off-label use of rituximab grew dramatically over the course of the study. With the recent FDA approval of the rituximab biosimilar and its expected lower price, off-label use will likely continue to rise. Opportunities for cost savings and to ensure appropriate use of these medications should be evaluated. DISCLOSURES: This study was funded by Kaiser Permanente. All authors except Hansen are employed by Kaiser Permanente. Hansen has nothing to disclose. Preliminary results were presented at the Mountain States Conference for Residents and Preceptors in May 2019 in Salt Lake City, UT, and at an encore presentation October 2019 at the American College of Clinical Pharmacy Annual Meeting in New York, NY.

Neutrophil extracellular traps contribute to the pathogenesis of leprosy type 2 reactions.

Up to 50% of patients with the multibacillary form of leprosy are expected to develop acute systemic inflammatory episodes known as type 2 reactions (T2R), thus aggravating their clinical status. Thalidomide rapidly improves T2R symptoms. But, due to its restricted use worldwide, novel alternative therapies are urgently needed. The T2R triggering mechanisms and immune-inflammatory pathways involved in its pathology remain ill defined. In a recent report, we defined the recognition of nucleic acids by TLR9 as a major innate immunity pathway that is activated during T2R. DNA recognition has been described as a major inflammatory pathway in several autoimmune diseases, and neutrophil DNA extracellular traps (NETs) have been shown to be a prime source of endogenous DNA. Considering that neutrophil abundance is a marked characteristic of T2R lesions, the objective of this study was to investigate NETs production in T2R patients based on the hypothesis that the excessive NETs formation would play a major role in T2R pathogenesis. Abundant NETs were found in T2R skin lesions, and increased spontaneous NETs formation was observed in T2R peripheral neutrophils. Both the M. leprae whole-cell sonicate and the CpG-Hlp complex, mimicking a mycobacterial TLR9 ligand, were able to induce NETs production in vitro. Moreover, TLR9 expression was shown to be higher in T2R neutrophils, suggesting that DNA recognition via TLR9 may be one of the pathways triggering this process during T2R. Finally, treatment of T2R patients with thalidomide for 7 consecutive days resulted in a decrease in all of the evaluated in vivo and ex vivo NETosis parameters. Altogether, our findings shed light on the pathogenesis of T2R, which, it is hoped, will contribute to the emergence of novel alternative therapies and the identification of prognostic reactional markers in the near future.

Increased CD5+ B-cells are associated with autoimmune phenomena in lepromatous leprosy patients.

BACKGROUND AND OBJECTIVE: Leprosy is a chronic slowly progressive infection caused by Mycobacterium leprae that primarily affects the skin and peripheral nerves. Lepromatous leprosy is characterized by absence of T-cell responses to M. leprae and advanced clinical disease. It is frequently associated with the presence of autoantibodies, which might be related to CD19+CD5+ and CD19+CD5- B lymphocyte percentages. Therefore, the aim of this study was to evaluate the percentages of CD19+CD5+ and CD19+CD5- B cell subsets as well as the total B cells in lepromatous leprosy patients. MATERIALS AND METHODS: Twenty lepromatous leprosy patients and ten healthy subjects served as control were included in this study. Venous blood samples were analyzed by flow cytometry to determine the B cell subsets and total B cell percentages. RESULTS: Compared to healthy controls, the percentages of CD19+CD5+ B cell subset and total B cells were found to be significantly higher in the patient group. While, the percentage of CD19+CD5- B cell subset was found to be higher in the patient group than the control without any significantly difference. Regarding the eye affection, the percentage of total B cells was observed to be significantly higher in affected patients compared to the non-affected group. CONCLUSION: The observed significant increases in CD19+CD5+ and total B cell percentages in patients with lepromatous leprosy suggests a possible role of these cells in the disorganized protective immune response as well as the development of eye complications in these patients.

Nail changes in autoimmune blistering disorders: A case-control study.

BACKGROUND: Pemphigus and pemphigoid disorders produce blistering cutaneous lesions. Earlier case reports state that nail involvement is uncommon in these autoimmune blistering disorders. AIMS AND OBJECTIVES: To study nail changes in autoimmune blistering disorders. METHODS: A case-control study was conducted where 40 cases and 40 controls were evaluated for nail changes. RESULTS: Nail changes were seen in 72.5% of cases and 17.5% of controls. The most common nail findings were paronychia and onychorrhexis. LIMITATIONS: Small sample size; short study duration; nail biopsy could not be done. CONCLUSION: Our findings indicate that the inflammatory nature of the blistering cutaneous disease is often reflected conspicuously in the nails.

Chinese version of the treatment of autoimmune bullous disease quality of life questionnaire: Reliability and validity.

BACKGROUND: Treatments for autoimmune blistering disease carry significant risks of medical complications and can affect the patient's quality of life. Recently, the Treatment of Autoimmune Bullous Disease Quality of Life questionnaire was developed in Australia. OBJECTIVE: The objective of this study was to evaluate the reliability and validity of the Chinese version of the Treatment of Autoimmune Bullous Disease Quality of Life questionnaire in Chinese patients with autoimmune blistering diseases. METHODS: The Chinese version of the Treatment of Autoimmune Bullous Disease Quality of Life questionnaire was produced by forward-backward translation and cross-cultural adaptation of the original English version. Autoimmune blistering disease patients recruited in the study self-administered the Chinese Treatment of Autoimmune Bullous Disease Quality of Life questionnaire, the Dermatology Life Quality Index and the 36-item Short-Form Health Survey. Reliability of the Chinese Treatment of Autoimmune Bullous Disease Quality of Life was evaluated using internal consistency and test-retest (days 0 and 7) methods. Validity was analyzed by face, content, construct, convergent and discriminant validity measures. RESULTS: A total of 86 autoimmune blistering disease patients were recruited for the study. Cronbach's alpha coefficient was 0.883 and the intraclass correlation coefficient was 0.871. Face and content validities were satisfactory. Convergent validity testing revealed correlation coefficients of 0.664 for the Treatment of Autoimmune Bullous Disease Quality of Life and Dermatology Life Quality Index and -0.577 for the Treatment of Autoimmune Bullous Disease Quality of Life and 36-item Short-Form Health Survey. With respect to discriminant validity, no significant differences were observed in the Treatment of Autoimmune Bullous Disease Quality of Life scores of men and women (t = 0.251, P = 0.802), inpatients and outpatients (t = 0.447, P = 0.656), patients on steroids and steroid-sparing medications (t = 0.672, P = 0.503) and patients with different autoimmune blistering disease subtypes (F = 0.030, P = 0.971). LIMITATIONS: Illiterate patients were excluded from the study. The patients were from a single hospital and most of their conditions were in a relatively stable status. CONCLUSION: The Chinese version of the Treatment of Autoimmune Bullous Disease Quality of Life questionnaire is a reliable and valid instrument to measure treatment burden and to serve as an end point in clinical trials in Chinese autoimmune blistering disease patients.

A Brighter Side to Thalidomide: Its Potential Use in Immunological Disorders.

Thalidomide and its derivatives are immunomodulatory drugs (IMiDs) known for their sedative, teratogenic, anti-angiogenic, and anti-inflammatory properties. Commonly used in the treatment of cancers such as multiple myeloma and myelodysplastic syndrome (MDS), IMiDs have also been used in the treatment of an inflammatory skin pathology associated with Hansen's disease/leprosy. They have also shown promise in the treatment of autoimmune disorders including systemic lupus erythmatosus (SLE) and inflammatory bowel disease (IBD). Recent structural and experimental observations have revolutionized our understanding of these properties by revealing the fundamental molecular events underpinning IMiD activity. We review these findings, their relevance to IMiD therapy in immunological disorders, and discuss how further research might unlock the vast clinical potential of these compounds.

Skin diseases of the nose.

OBJECTIVES: The goal of this study was to review the main lesion types of the nasal skin and appropriate treatment strategies rather than to present a comprehensive list of all diseases that affect the skin that can involve the nose. METHODS: We reviewed the main nasal skin lesion types and available treatment strategies. Nasal skin lesions were classified as benign, premalignant, or malignant. RESULTS: Benign lesions of the nose include nonmalignant tumoral lesions (i.e., freckles, comedo, adenoma sebaceum [Pringle disease], hydrocystoma, fibrous papules, sebaceous hyperplasia, and rhinophyma), autoimmune and inflammatory conditions (i.e., pemphigus, sarcoidosis, systemic lupus erythematosus, facial eosinophilic granuloma, rosacea, herpes zoster infection, leishmaniasis, and leprosy), and vascular lesions (i.e., telangiectasis, hemangioma, and spider nevus). Premalignant lesions are actinic keratosis and keratoacanthoma; and malignant tumors are melanoma, basal cell carcinoma, and squamous cell carcinoma. Regardless of whether or not they are malignant, all facial lesions can yield significant cosmetic discomfort that should be evaluated carefully before commencing any curative or corrective intervention. In general, benign lesions are treated with dermabrasive modalities, such as trichloroacetic acid, phenol, salicylate, and laser ablation. Electrocautery, cryosurgery, and surgical excision are also used, although these methods may result in scar formation, which can sometimes be more problematic than the original lesion itself. CONCLUSION: Any disease that affects the skin, especially those diseases that are triggered by ultraviolet exposure, can involve the face and nose. Cosmetic defects due both to the lesion itself and the intervention must be discussed with the patient, preferably in the presence of a first-degree relative, before commencement of treatment. As a result of heterogeneity of skin lesions of the nose, appropriate education of general practitioners as well as otorhinolaryngologists is mandatory.

Clinical, demographic and immunopathological spectrum of subepidermal autoimmune bullous diseases at a tertiary center: A 1-year audit.

BACKGROUND: The subepidermal autoimmune bullous diseases are a subset of immunobullous diseases encountered less frequently in the Indian population. There is a paucity of data on the prevalence, demographic and clinicopathological spectrum of various subepidermal autoimmune bullous diseases from India. AIM: To determine the demographic and clinicopathological profile of subepidermal autoimmune bullous diseases in Indian patients, presenting to the Immunobullous Disease Clinic of Postgraduate Institute of Medical Education and Research, Chandigarh. METHODS: Patients seen from November 2013 to November 2014 who fulfilled the preset diagnostic criteria of subepidermal autoimmune bullous diseases were identified from case records. Data regarding demographic characteristics, clinical profile, immunopathological findings and treatment were collected from the predesigned proforma. RESULTS: Of 268 cases of autoimmune bullous diseases registered, 50 (18.7%) were subepidermal autoimmune bullous diseases. Bullous pemphigoid was most frequently seen in 20 (40%) cases, followed by dermatitis herpetiformis in 14 (28%), mucous membrane pemphigoid in 6 (12%), chronic bullous dermatosis of childhood / linear immunoglobulin A bullous dermatosis in 5 (10%), lichen planus pemphigoides in 3 (6%), pemphigoid gestationis and epidermolysis bullosa acquisita in 1 (2%) case each. None of the patients had bullous systemic lupus erythematosus. LIMITATIONS: We could not perform direct and indirect immunofluorescence using salt-split skin as a substrate and immunoblotting due to non-availability of these facilities. Therefore, misclassification of subepidermal autoimmune bullous diseases in some cases cannot be confidently excluded. CONCLUSION: Subepidermal autoimmune bullous diseases are not uncommon in Indian patients. Bullous pemphigoid contributes maximally to the burden of subepidermal autoimmune bullous diseases in India, similar to that in the West, although the proportion is lower and disease onset is earlier. Dermatitis herpetiformis was observed to have a higher prevalence in our population, compared to that in the West and the Far East countries. The prevalence of other subepidermal autoimmune bullous diseases is relatively low. Detailed immunofluorescence and immunoblotting studies on larger patient numbers would help better characterize the pattern of subepidermal autoimmune bullous diseases and their features in Indian patients.

The TNF-family cytokine TL1A: from lymphocyte costimulator to disease co-conspirator.

Originally described in 2002 as a T cell-costimulatory cytokine, the tumor necrosis factor family member TNF-like factor 1A (TL1A), encoded by the TNFSF15 gene, has since been found to affect multiple cell lineages through its receptor, death receptor 3 (DR3, encoded by TNFRSF25) with distinct cell-type effects. Genetic deficiency or blockade of TL1A-DR3 has defined a number of disease states that depend on this cytokine-receptor pair, whereas excess TL1A leads to allergic gastrointestinal inflammation through stimulation of group 2 innate lymphoid cells. Noncoding variants in the TL1A locus are associated with susceptibility to inflammatory bowel disease and leprosy, predicting that the level of TL1A expression may influence host defense and the development of autoimmune and inflammatory diseases.