The K veim response: still useful, still a puzzle

The role of neutrophils in the pathogenesis of Crohn's disease

Crohn's disease (CD) is caused by a trigger, almost certainly enteric infection by one of a multitude of organisms that allows faeces access to the tissues, at which stage the response of individuals predisposed to CD is abnormal. In CD the failure of acute inflammation results in the failure to recruit neutrophils to the inflammatory site, as a consequence of which the clearance of bacteria from the tissues is defective. The retained faecal products result in the characteristic chronic granulomatous inflammation and adaptive immune response. Impaired of digestion of bacteria and fungi by CGD neutrophils can result in a similar pathological and clinical picture. The neutrophils in CD are normal and their inadequate accumulation at sites of inflammation generally results from diminished secretion of proinflammatory cytokines by macrophages consequent upon disordered vesicle trafficking.

Atypical Cutaneous Presentations of Sarcoidosis: Two Case Reports and Review of the Literature

PURPOSE OF REVIEW

The goal of this review is to provide the reader with an updated summary of the cutaneous manifestations of systemic sarcoidosis, with a particular emphasis on the predilection of sarcoidosis for scars, tattoos, and other areas of traumatized skin.

RECENT FINDINGS

While the mechanism underlying the propensity for traumatized skin to develop sarcoidosis lesions remains unclear, several theories have been proposed including the idea that cutaneous sarcoidosis represents an exuberant, antigen-driven foreign-body response, as well as the theory that traumatized skin represents an immunocompromised district with altered local immune trafficking and neural signaling. In this review, we present two cases in which the development of cutaneous lesions in scars and tattoos was integral to the diagnosis of systemic sarcoidosis. We then review the various cutaneous manifestations of systemic sarcoidosis, the clinical characteristics and differential diagnosis of scar and tattoo sarcoidosis, the proposed mechanism by which traumatized skin is prone to developing sarcoidosis lesions, and current treatments for cutaneous sarcoidosis.

Making sense of the cause of Crohn's - a new look at an old disease

The cause of Crohn’s disease (CD) has posed a conundrum for at least a century. A large body of work coupled with recent technological advances in genome research have at last started to provide some of the answers. Initially this review seeks to explain and to differentiate between bowel inflammation in the primary immunodeficiencies that generally lead to very early onset diffuse bowel inflammation in humans and in animal models, and the real syndrome of CD. In the latter, a trigger, almost certainly enteric infection by one of a multitude of organisms, allows the faeces access to the tissues, at which stage the response of individuals predisposed to CD is abnormal. Direct investigation of patients’ inflammatory response together with genome-wide association studies (GWAS) and DNA sequencing indicate that in CD the failure of acute inflammation and the clearance of bacteria from the tissues, and from within cells, is defective. The retained faecal products result in the characteristic chronic granulomatous inflammation and adaptive immune response. In this review I will examine the contemporary evidence that has led to this understanding, and look for explanations for the recent dramatic increase in the incidence of this disease.

Making sense of the cause of Crohn's - a new look at an old disease

The cause of Crohn's disease (CD) has posed a conundrum for at least a century. A large body of work coupled with recent technological advances in genome research have at last started to provide some of the answers. Initially this review seeks to explain and to differentiate between bowel inflammation in the primary immunodeficiencies that generally lead to very early onset diffuse bowel inflammation in humans and in animal models, and the real syndrome of CD. In the latter, a trigger, almost certainly enteric infection by one of a multitude of organisms, allows the faeces access to the tissues, at which stage the response of individuals predisposed to CD is abnormal. Direct investigation of patients' inflammatory response together with genome-wide association studies (GWAS) and DNA sequencing indicate that in CD the failure of acute inflammation and the clearance of bacteria from the tissues, and from within cells, is defective. The retained faecal products result in the characteristic chronic granulomatous inflammation and adaptive immune response. In this review I will examine the contemporary evidence that has led to this understanding, and look for explanations for the recent dramatic increase in the incidence of this disease.

Etiologies of Sarcoidosis

Since sarcoidosis was first described more than a century ago, the etiologic determinants causing this disease remain uncertain. Studies suggest that genetic, host immunologic, and environmental factors interact together to cause sarcoidosis. Immunologic characteristics of sarcoidosis include non-caseating granulomas, enhanced local expression of T helper-1 (and often Th17) cytokines and chemokines, dysfunctional regulatory T-cell responses, dysregulated Toll-like receptor signaling, and oligoclonal expansion of CD4+ T cells consistent with chronic antigenic stimulation. Multiple environmental agents have been suggested to cause sarcoidosis. Studies from several groups implicate mycobacterial or propionibacterial organisms in the etiology of sarcoidosis based on tissue analyses and immunologic responses in sarcoidosis patients. Despite these studies, there is no consensus on the nature of a microbial pathogenesis of sarcoidosis. Some groups postulate sarcoidosis is caused by an active viable replicating infection while other groups contend there is no clinical, pathologic, or microbiologic evidence for such a pathogenic mechanism. The authors posit a novel hypothesis that proposes that sarcoidosis is triggered by a hyperimmune Th1 response to pathogenic microbial and tissue antigens associated with the aberrant aggregation of serum amyloid A within granulomas, which promotes progressive chronic granulomatous inflammation in the absence of ongoing infection.

Development of a T7 Phage Display Library to Detect Sarcoidosis and Tuberculosis by a Panel of Novel Antigens

Sarcoidosis is a granulomatous inflammatory disease, diagnosed through tissue biopsy of involved organs in the absence of other causes such as tuberculosis (TB). No specific serologic test is available to diagnose and differentiate sarcoidosis from TB. Using a high throughput method, we developed a T7 phage display cDNA library derived from mRNA isolated from bronchoalveolar lavage (BAL) cells and leukocytes of sarcoidosis patients. This complex cDNA library was biopanned to obtain 1152 potential sarcoidosis antigens and a microarray was constructed to immunoscreen two different sets of sera from healthy controls and sarcoidosis. Meta-analysis identified 259 discriminating sarcoidosis antigens, and multivariate analysis identified 32 antigens with a sensitivity of 89% and a specificity of 83% to classify sarcoidosis from healthy controls. Additionally, interrogating the same microarray platform with sera from subjects with TB, we identified 50 clones that distinguish between TB, sarcoidosis and healthy controls. The top 10 sarcoidosis and TB specific clones were sequenced and homologies were searched in the public database revealing unique epitopes and mimotopes in each group. Here, we show for the first time that immunoscreenings of a library derived from sarcoidosis tissue differentiates between sarcoidosis and tuberculosis antigens. These novel biomarkers can improve diagnosis of sarcoidosis and TB, and may aid to develop or evaluate a TB vaccine.

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Immunity plays a major role in a vast array of human diseases.

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Sarcoidosis shares similarities with non-infectious and infectious granulomatous diseases, including tuberculosis.

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A highly sensitive and specific T7 phage library discriminates the immune signature between sarcoidosis patients and TB.

On the nature of sarcoidosis

More than 140 years since its recognition as a clinical entity, sarcoidosis remains enigmatic. Its classification as a disease vs. a syndrome is uncertain. Its etiology remains undefined. The "immune paradox" (delayed type hypersensitivity anergy in a setting of exuberant systemic granulomatous response) resists explanation. Its relationship to the Kveim test is poorly understood. Its prognostic determinants and treatment indications are among the unsolved or disputed problems. Immunological investigations generated the thesis that the characterizing systemic granuloma arise as a fallback reaction to inefficient cellular immune processing, due most often to impaired myeloid dendritic cell function of unknown cause. The concept that sarcoidosis represents a (genetically conditioned) default to a more primitive immunological response provides a unifying explanation for its development in persons with a variety of antigenic exposures and in individuals with cellular immune deficiencies. It furnishes a coherent explanation for the apparent paradox that individuals exhibiting the most intense cellular response experience the most favorable outcomes and for the adverse effect of corticosteroid-suppression in recent onset sarcoidosis.

Sarcoidosis--scientific progress and clinical challenges

Sarcoidosis is an uncommon systemic inflammatory disorder characterized by noncaseating granulomatous inflammation that most commonly affects the lungs, intrathoracic lymph nodes, eyes and skin. One-third or more of patients with sarcoidosis have chronic, unremitting inflammation with progressive organ impairment. Findings of family and genetic studies indicate a genetic susceptibility to sarcoidosis, with genes in the MHC region having a dominant role. Immunologic hallmarks of the disease include highly polarized expression of cytokines produced by type 1 T helper cells and tumor necrosis factor (TNF) at sites of inflammation. Increasing evidence obtained within the past decade suggests the etiology of sarcoidosis predominantly involves microbial triggers, with the most convincing data implicating mycobacterial or propionibacterial organisms. Innate immune mechanisms, possibly involving misfolding and aggregation of serum amyloid A, might have a critical role in the pathobiology of sarcoidosis. Despite these advances, there are no clinically useful biomarkers that can assist the clinician in diagnosis, prognosis or assessment of treatment effects. Corticosteroids remain the cornerstone of therapy when organ function is threatened or progressively impaired. The role of immunosuppressive drugs and anti-TNF agents in the treatment of sarcoidosis remains uncertain, and there are no FDA-approved therapies. Meaningful progress in developing clinically useful tools and new therapies will depend on further advances in understanding the pathogenesis of sarcoidosis and its disease-specific pathways.

Serum amyloid A regulates granulomatous inflammation in sarcoidosis through Toll-like receptor-2

RATIONALE

The critical innate immune mechanisms that regulate granulomatous inflammation in sarcoidosis are unknown. Because the granuloma-inducing component of sarcoidosis tissues has physicochemical properties similar to those of amyloid fibrils, we hypothesized that host proteins capable of forming poorly soluble aggregates or amyloid regulate inflammation in sarcoidosis.

OBJECTIVES

To determine the role of the amyloid precursor protein, serum amyloid A, as an innate regulator of granulomatous inflammation in sarcoidosis.

METHODS

Serum amyloid A expression was determined by immunohistochemistry in sarcoidosis and control tissues and by ELISA. The effect of serum amyloid A on nuclear factor (NF)-kappaB induction, cytokine expression, and Toll-like receptor-2 stimulation was determined with transformed human cell lines and bronchoalveolar lavage cells from patients with sarcoidosis. The effects of serum amyloid A on regulating helper T cell type 1 (Th1) granulomatous inflammation were determined in experimental models of sarcoidosis, using Mycobacterium tuberculosis catalase-peroxidase.

MEASUREMENTS AND MAIN RESULTS

We found that the intensity of expression and distribution of serum amyloid A within sarcoidosis granulomas was unlike that in many other granulomatous diseases. Serum amyloid A localized to macrophages and giant cells within sarcoidosis granulomas but correlated with CD3(+) lymphocytes, linking expression to local Th1 responses. Serum amyloid A activated NF-kappaB in Toll-like receptor-2-expressing human cell lines; regulated experimental Th1-mediated granulomatous inflammation through IFN-gamma, tumor necrosis factor, IL-10, and Toll-like receptor-2; and stimulated production of tumor necrosis factor, IL-10, and IL-18 in lung cells from patients with sarcoidosis, effects inhibited by blocking Toll-like receptor-2.

CONCLUSIONS

Serum amyloid A is a constituent and innate regulator of granulomatous inflammation in sarcoidosis through Toll-like receptor-2, providing a mechanism for chronic disease and new therapeutic targets.

Potential etiologic agents in sarcoidosis

The etiology of sarcoidosis remains uncertain. The hallmark of sarcoidosis is the epithelioid granuloma, which serves as a necessary starting point for considering disease etiology. Any etiologic agent of sarcoidosis must also explain the typical clinical behaviors and characteristic immunopathologic features of the disease. One clinical observation that serves as a bridge to the etiology of sarcoidosis is the Kveim reaction. In this reaction, local epithelioid granulomas develop several weeks after the intradermal injection of homogenates of sarcoidosis tissue. Our group capitalized on the known properties of the Kveim reagent to search for candidate pathogenic tissue antigens in sarcoidosis without other a priori hypotheses regarding possible microbial or autoimmune etiologies. Using a limited proteomics approach based on the physicochemical properties of Kveim reagent, we detected a limited number of poorly soluble antigenic proteins in sarcoidosis tissues by protein immunoblotting, using sarcoidosis sera. Matrix-associated laser desorption/ionization-time of flight mass spectrometry identified one of these antigens to be the Mycobacterium tuberculosis catalase-peroxidase protein (mKatG). We found IgG responses to recombinant mKatG in more than 50% of patients with sarcoidosis but rarely in purified protein derivative (PPD)-negative control subjects. These findings support the conclusion that mKatG is a tissue antigen and target of the adaptive immune response in sarcoidosis, providing further evidence of a mycobacterial etiology in a subset of sarcoidosis. More generally, the approach used in these studies might be employed to discover and validate other candidate pathogenic antigens in sarcoidosis or other granulomatous disorders.

Differences in clinical findings between Caucasians and African Americans with biopsy-proven sarcoidosis

OBJECTIVE

To study the prevalence of ocular manifestations in African American and Caucasian patients with biopsy-proven sarcoidosis at the initial ophthalmic examination and to determine the relationship between angiotensin-converting enzyme (ACE) levels, chest x-ray findings, and ocular signs of sarcoidosis.

DESIGN

Retrospective, cross-sectional, observational study.

PARTICIPANTS

Eighty-one consecutive patients with biopsy-proven sarcoidosis seen at the Doheny Eye Institute from January 1989 through April 2005.

METHODS

Medical records were reviewed to obtain demographic data, biopsy site, initial ocular findings, pulmonary symptoms, and results of serum ACE levels and chest x-rays. Associations between ACE level/chest x-ray stages and ocular manifestations related to sarcoidosis were obtained from these data.

MAIN OUTCOME MEASURES

Ocular manifestations related to sarcoidosis.

RESULTS

Of the 81 patients, 35 were Caucasian; 29 were African American; and the remaining 17 were Hispanic, Asian Indian, and other races. Female patients were older than males (P = 0.05). Sixty-five (80%) of the 81 patients had ocular manifestations related to sarcoidosis. Thirty-three patients (40.7%) had uveitis, 12 (14.8%) had adnexal granulomas, and 25 (30.8%) had keratoconjunctivitis sicca. Of the 33 patients with uveitis, 22 presented with nongranulomatous inflammation. There was no significant association between ocular manifestations related to sarcoidosis and serum ACE levels (P = 0.43) or chest x-ray stage (P>0.99). Of the 29 African American patients, 26 (89.7%) had ocular manifestations related to sarcoidosis, compared with 24 (68.6%) of the 35 Caucasians (P = 0.12). The African American patients were younger (mean age, 44.4 years) than the Caucasian patients (mean age, 52.0) (P = 0.003) and had higher mean ACE levels (P = 0.003). A significantly high proportion of African American males presented with uveitis (P = 0.005), and a significantly high proportion of African American females presented with adnexal granulomas (P = 0.05).

CONCLUSIONS

The present study reveals that patients with sarcoidosis can present initially with clinical features of nongranulomatous uveitis. Relative to Caucasians, African American patients with sarcoidosis tend to be younger when they first present to the ophthalmologist and to present with uveitis and/or adnexal granuloma. Serum ACE levels and chest x-ray stages may not help predict the occurrence of ocular changes in sarcoidosis.

Mycobacterial catalase-peroxidase is a tissue antigen and target of the adaptive immune response in systemic sarcoidosis

Sarcoidosis is a disease of unknown etiology characterized by noncaseating epithelioid granulomas, oligoclonal CD4(+) T cell infiltrates, and immune complex formation. To identify pathogenic antigens relevant to immune-mediated granulomatous inflammation in sarcoidosis, we used a limited proteomics approach to detect tissue antigens that were poorly soluble in neutral detergent and resistant to protease digestion, consistent with the known biochemical properties of granuloma-inducing sarcoidosis tissue extracts. Tissue antigens with these characteristics were detected with immunoglobulin (Ig)G or F(ab')(2) fragments from the sera of sarcoidosis patients in 9 of 12 (75%) sarcoidosis tissues (150-160, 80, or 60-64 kD) but only 3 of 22 (14%) control tissues (all 62-64 kD; P = 0.0006). Matrix-assisted laser desorption/ionization time of flight mass spectrometry identified Mycobacterium tuberculosis catalase-peroxidase (mKatG) as one of these tissue antigens. Protein immunoblotting using anti-mKatG monoclonal antibodies independently confirmed the presence of mKatG in 5 of 9 (55%) sarcoidosis tissues but in none of 14 control tissues (P = 0.0037). IgG antibodies to recombinant mKatG were detected in the sera of 12 of 25 (48%) sarcoidosis patients compared with 0 of 11 (0%) purified protein derivative (PPD)(-) (P = 0.0059) and 4 of 10 (40%) PPD(+) (P = 0.7233) control subjects, suggesting that remnant mycobacterial catalase-peroxidase is one target of the adaptive immune response driving granulomatous inflammation in sarcoidosis.

Sarcoid heart disease: clinical course and treatment

Sarcoidosis is a rare granulomatous disease of unknown etiology that can affect any organ. Cardiac involvement, although uncommon, has a wide spectrum of clinical manifestations and is potentially fatal. Although there is no agreement upon a strategy for the diagnosis (which is difficult to make based on clinical information alone), the introduction of newer technology is promising and may be useful both for the early diagnosis of cardiac involvement and for the evaluation of response to therapy. Early treatment is crucial in improving symptoms and prognosis. ICD implantation and cardiac transplantation may offer improvements in management, as steroid therapy and pacemaker implantation has led to improved outcomes over the past three decades.

Eight fundamental unsolved problems in sarcoidosis

More than 100 years since the identification and characterization of sarcoidosis, its etiology, fundamental nature, pathogenesis, incidence, ethnic predilections, relationship to the Kveim test and prognostic determinants remain largely either unknown or unexplained, and treatment indications, absent compelling findings, remain undefined. Professor Hilbert's "Address" delineates these fundamental deficits in our knowledge and understanding.

Löfgren's syndrome revisited: a study of 186 patients

PURPOSE

To evaluate the clinical features, the results of noninvasive tests and biopsies, and the outcome of patients with Löfgren's syndrome.

SUBJECTS AND METHODS

Patients diagnosed as having Löfgren's syndrome at a university hospital in Barcelona, Spain, from 1974 to 1996, were prospectively followed. Löfgren's syndrome was defined as the association of erythema nodosum or periarticular ankle inflammation with unilateral or bilateral hilar or right paratracheal lymphadenopathy.

RESULTS

Löfgren's syndrome was diagnosed in 186 patients. The mean age was 37 +/- 11 years, and 157 (85%) were women. In 91 patients (49%), symptoms started during the spring (P < 0.0001). Erythema nodosum, periarticular ankle inflammation, or both were present at onset in 173 patients (93%). At the time of diagnosis, 161 patients (87%) had no respiratory symptoms; 151 (81%) had stage I abnormalities on chest radiograph, 29 (16%) stage II, and 6 (3%) stage 0. Five percent of patients had decreased forced vital capacity, and 15% had decreased carbon monoxide diffusing capacity. Extrathoracic involvement was infrequent. Serum angiotensin-converting enzyme levels were increased in 50% of patients. Gallium-67 scans showed hilar uptake in all the studied patients, but it yielded useful additional diagnostic information only in those with normal chest radiographs or with unilateral hilar lymphadenopathy. The diagnosis was proven with biopsy results in 63% of patients. None of the patients without histologic confirmation were subsequently found to have a diagnosis other than sarcoidosis. In the 133 patients who were followed for a mean of almost 5 years, 11 (8%) continued to have active disease, and 8 (6%) had several recurrences between 18 months and 20 years after a complete resolution. A normal serum angiotensin-converting enzyme level at diagnosis was associated with disease resolution without recurrence.

CONCLUSION

Löfgren's syndrome is usually a self-limiting form of sarcoidosis. Histologic confirmation is not necessary in typical cases. In a small number of patients, the disease may remain active or recur long after its onset, although usually with mild organ dysfunction.

Etiology of sarcoidosis

Since sarcoidosis was first recognized as a distinct clinical entity, investigators have speculated that a transmissible agent may cause sarcoidosis. Recent attempts at directly isolating infectious organisms or indirectly detecting microbial DNA or RNA from sarcoid tissue have led to inconclusive results. Studies on the immunopathogenic origins of sarcoidosis have provided evidence of persistent antigenic stimulation at sites of inflammation that are associated with dysregulated cytokine production. To date, however, the challenge of defining the cause of sarcoidosis remains unmet.

Relationship between presentation of sarcoidosis and T lymphocyte profile. A study in bronchoalveolar lavage fluid

One hundred patients with histologically verified sarcoidosis were studied. They were divided into three groups, based on their clinical presentation and smoking status. Group A consisted of patients whose disease was detected by routine chest x-ray film, without symptoms; group B included those with respiratory and general constitutional symptoms; and group C included patients with erythema nodosum and/or arthralgia and hilar lymphadenopathy. Group A showed an increased CD4/CD8 ratio of 4.7 +/- 1.1; group B, 8.0 +/- 1.2; and group C counted for the highest ratio of 10.7 +/- 1.5. Cigarette smoking modifies the immunologic bronchoalveolar lavage (BAL) fluid sample profile, since alveolitis was less pronounced in smokers. In addition, BAL fluid samples obtained from sarcoidosis patients with hilar lymphadenopathy showed the most characteristic features of alveolitis, suggesting a disseminated instead of a local immune response. Therefore, the clinical presentation of sarcoidosis and the smoking status of a sarcoidosis patient are crucial for interpreting individual lavage analysis results.

Positive Kveim test in patients with coexisting sarcoidosis and human immunodeficiency virus infection

We present two cases of sarcoidosis complicated by HIV infection. Each case had a different level of sarcoidosis activity and coexisted with either an AIDS-related infection or a HIV-positive state. Manifestations of sarcoidosis were not apparent in the patient with the AIDS-defining opportunistic infection, but were active in the patient with asymptomatic HIV infection. Both patients had granulomatous reactions to Kveim antigen, and one had such a reaction following an AIDS-defining infection. These findings suggest that non-T-cell mechanisms may be involved in granuloma formation in sarcoidosis.

Nonviable autologous bronchoalveolar lavage cell preparations induce intradermal epithelioid cell granulomas in sarcoidosis patients

Intracutaneous injection of sarcoidosis patients with Kveim-Siltzbach antigen (KSAg), a particulate suspension of granulomatous sarcoidal spleen, induces an influx of T-helper lymphocytes and monocyte-macrophages followed by epithelioid cell granuloma formation. In the lung, similar granulomas form from an alveolitis of similar mononuclear cells, which may harbor a Kveim-like granulomagenic factor. To assess this possibility, preparations of nonviable autologous bronchoalveolar lavage cells (NABC) and KSAg were injected intracutaneously at different sites and biopsied at 4 to 5 wk. Of 22 sarcoidosis patients, nine (41%) developed typical granulomas at the NABC site, while all developed granulomas at the KSAg site. Responders to NABC had more recent onset of symptoms than nonresponders (3.2 versus 23.7 months, p less than 0.01), but did not have significantly higher percentages of lavage lymphocytes or more rosetting of lymphocytes about alveolar macrophages. None of 11 normal volunteers developed granulomas in response to NABC. Epithelioid cell granulomas at NABC and KSAg sites were similar by hematoxylin-eosin staining and by biotin-avidin-peroxidase immunohistochemical staining with monoclonal antibodies Leu-1, Leu-14, Leu-2a, Leu-3a, anti-interleukin-2 receptor, and polyclonal antibodies against lysozyme and alpha 1-anti-chymotrypsin. Symptomatic onset of sarcoidosis is associated with an autologous lavage cell factor that induces intradermal epithelioid cell granulomas that are immunophenotypically similar to Kveim-induced granulomas.

Counts of S-100 positive epidermal dendritic cells in Kveim test skin biopsies

S-100 positive epidermal dendritic cells were counted in skin biopsies from 48 Kveim tests and four known foreign-body reactions. Counts in histologically positive Kveim biopsies (mean 11.3 per 200 basal cells) were significantly higher than in either negative biopsies (5.1; P less than 0.001) or foreign-body reactions (4.7; P less than 0.05). A similar difference was found, irrespective of the histological appearances, between biopsies from patients diagnosed clinically as having sarcoidosis (10.5) and those in which another diagnosis had been made (4.1; P less than 0.001). In biopsies from patients with sarcoidosis 70% had a positive Kveim test, 70% had a raised epidermal dendritic cell count and one or the other was positive in 90%. All cases in which both the Kveim test was positive and the dendritic cell count was raised had a final clinical diagnosis of sarcoidosis. Counts of S-100 positive epidermal dendritic cells are useful in differentiating positive reactions to Kveim suspension from non-specific reactions to foreign material and increase the diagnostic confidence of the Kveim test.

Sarcoidosis: in search of Kveim reactivity in vitro

Granuloma formation in patients with sarcoidosis may be evoked by the intradermal injection of homogenised sarcoid tissue (the Kveim reaction). Attempts to demonstrate an in vitro counterpart of the reaction have been unsuccessful. The cytokine interleukin-2 (IL-2) enhances immune responses in vivo and in vitro. We report here an attempt to amplify the Kveim reaction by the addition of IL-2. We studied the effect of Kveim reagent on the proliferative responses of peripheral blood mononuclear cells (PBMC) in the presence or absence of exogenous IL-2. Twenty-eight patients were studied and 14 healthy subjects served as controls. PBMC were cultured, in vitro, in the presence of Kveim reagent. Recombinant IL-2 or both of these combined. Proliferative responses were measured by [3H]-thymidine incorporation. The response of patients' PBMC in the presence of Kveim reagent at a dilution of 1:40 was significantly below the unstimulated response (P less than 0.01). Kveim reagent at a dilution of 1:40 also inhibited the proliferative response of patients PBMC to IL-2 (P less than 0.005); greater dilutions (1:100 and 1:1000) of Kveim reagent were not inhibitory. Responses of PBMC from control subjects (both unstimulated and IL-2 generated) were reduced in the presence of Kveim reagent, however, these reductions were not statistically significant.