Il-4 and IFN-gamma mRNA induction in human peripheral lymphocytes specific for beta-lactam antibiotics in immediate or delayed hypersensitivity reactions

Value of the Lymphocyte Transformation Test for the Diagnosis of Drug-Induced Hypersensitivity Reactions in Hospitalized Patients with Severe COVID-19

In the first wave of COVID-19, up to 20% of patients had skin lesions with variable characteristics. There is no clear evidence of the involvement of the SARS-CoV-2 virus in all cases; some of these lesions may be secondary to drug hypersensitivity. To analyze the possible cause of the skin lesions, we performed a complete allergology study on 11 patients. One year after recovery from COVID-19, we performed a lymphocyte transformation test (LTT) and Th1/Th2 cytokine secretion assays for PBMCs. We included five nonallergic patients treated with the same drugs without lesions. Except for one patient who had an immediate reaction to azithromycin, all patients had a positive LTT result for at least one of the drugs tested (azithromycin, clavulanic acid, hydroxychloroquine, lopinavir, and ritonavir). None of the nonallergic patients had a positive LTT result. We found mixed Th1/Th2 cytokine secretion (IL-4, IL-5, IL-13, and IFN-γ) in patients with skin lesions corresponding to mixed drug hypersensitivity type IVa and IVb. In all cases, we identified a candidate drug as the culprit for skin lesions during SARS-CoV-2 infection, although only three patients had a positive drug challenge. Therefore, it would be reasonable to recommend avoiding the drug in question in all cases.

Lymphocyte transformation test and cytokine detection assays: Determination of read out parameters for delayed-type drug hypersensitivity reactions

Drug hypersensitivity reactions (DHRs) occur in certain people and are often not predictable. DHRs can be classified as immediate and delayed reactions regarding to onset of clinical manifestations. Both reactions are considered to be an important public health problem because they can lead to life-threatening conditions; however, this review article will focus on delayed DHRs. The most important points for diagnosis of delayed DHRs are the recognition of drug hypersensitivity characteristics and culprit drug identification. While it is usually difficult to identify a culprit drug; clinical evaluation using the causality assessment method, a non-invasive process, can identify the culprit drug without the need for intensive investigation. Delayed DHRs can cause life-threatening conditions; therefore, in vivo skin tests, as well as drug provocation tests, have to be cautiously performed by a drug allergist and have not been recommended in uncontrolled conditions. ENDA/EAACI has recommended that in vitro tests (if available) be performed prior to any in vivo tests. Therefore, in vitro diagnostic tests can be alternative methods to identify a culprit drug for delayed DHR diagnosis as there is no or very low risk for patients under investigation. There are many testing approaches to identify causative agents for delayed DHRs such as: the lymphocyte transformation test (LTT), cytokine/mediator detection assays (i.e. ELISA and flow cytometry-based bead assays), multiplex bead-based immunoassay and ELISpot. The LTT is the most standardized method whereas it has been available in medical schools affiliated with university hospitals. Other in vitro tests, like cytokine detection assays, have also been used, even though they are still being evaluated. They could supplement LTT results that would provide drug allergist's with documentary evidence and prevent risk to patients by avoiding in vivo or drug provocation testing. Hence, the in vitro tests have been promising tests contributing to the management of the delayed DHR work-up process in clinical practice.

Lymphocyte transformation test: History and current approaches

Drug-induced hypersensitivity reactions encompass a variety of different clinical phenotypes ranging from harmless rashes to fatal reactions. They can be classified into allergic (i.e. drug allergy) and non-allergic reactions (i.e. non-allergic hypersensitivity). Drug allergies in turn can either be antibody (e.g. IgE) or T cell-mediated. One of the diagnostic tools for the in vitro detection of drug allergy is the lymphocyte transformation test (LTT) which is based on the activation and expansion of the drug-specific memory T cells following co-incubation of the patient's peripheral mononuclear cells (PMBC) with the suspected drug in vitro. The read-out parameter in the classical LTT is T cell proliferation which can be measured as counts per minute following the addition of radiolabeled thymidine to the cell culture. However, in the course of time different modifications of the classical LTT with regard to the read-out parameters and methods have been proposed. Likewise, variations of the LTT platform itself have been described in the literature. This review article describes the development of the classical LTT and its use in the context of drug allergy detection and summarizes the modifications which have been published over time.

Elevated Levels of Intelectin-1, a Pathogen-binding Lectin, in the BAL Fluid of Patients with Chronic Eosinophilic Pneumonia and Hypersensitivity Pneumonitis

Objective Human intelectin-1 (hITLN-1) binds to galactofuranosyl residues, which are present in the microbial cell wall, but which are absent in mammalian tissues, and has been suggested to play an immunological role against microorganisms. However, the involvement of hITLN-1 in the pathogenesis of diffuse pulmonary diseases remains unknown. The aim of this study was to compare the hITLN-1 concentrations in the bronchoalveolar lavage (BAL) fluid of patients with diffuse pulmonary diseases. Methods The cell components and concentrations of hITLN-1 were analyzed in the BAL fluid of 8 patients with idiopathic chronic eosinophilic pneumonia (ICEP), 3 patients with drug-induced eosinophilic pneumonia, 4 patients with hypersensitivity pneumonitis (HP), 11 patients with sarcoidosis, 9 patients with cryptogenic organizing pneumonia, and 5 patients with idiopathic fibrosing interstitial pneumonia (fibrosing nonspecific interstitial pneumonia or usual interstitial pneumonia). Results The hITLN-1 concentrations in the BAL fluid of patients with ICEP and HP were higher than in those with other diseases. In the ICEP group, no significant difference was observed in the hITLN-1 concentrations of patients with or without a history of bronchial asthma. Conclusion The results of the present study suggest that hITLN-1 may be involved in the pathogenesis of ICEP and HP, and that an increase in the hITLN-1 concentration in the BAL fluid may represent a new biomarker for these diseases.

[Pathogenic Mechanism and Diagnostic Testing for Drug Allergies]

　Three stages of the pathogenic mechanism of drug allergies can be considered: antigen formation, immune reaction and inflammation/disorder reaction. Drugs are thought to form 4 types of antigens: drug only, polymers, drug-carrier conjugates, and metabolite-carrier complexes. Antigens are recognized by B cell receptors and T cell receptors. Helper T cells (Th) are differentiated into four subsets, namely, Th1, Th2, Th17 and regulatory T cells (Treg). Th1 produces interleukin (IL)-2 and interferon (IFN)-γ, and activates macrophages and cytotoxic T cells (Tc). Macrophages induce type IV allergies, and Tc lead to serious type IV allergies. On the other hand, Th2 produces IL-4, IL-5, and IL-6, etc., and activates B cells. B cells produce IgE antibodies, and the IgE antibody affects mast cells and induces type I allergies. Activated eosinophil leads to the chronic state of type I allergy. Diagnostic testing for allergenic drugs is necessary for patients with drug allergies. Because in vivo diagnostic tests for allergenic drugs are associated with a risk and burden to the patient, in vitro allergy tests are recommended to identify allergenic drugs. In allergy tests performed in vitro, cytological tests are more effective than serological tests, and the leukocyte migration test (LMT) presently has the highest efficacy. An LMT-chamber is better than LMT-agarose in terms of usability and sensitivity, and it can detect about 80% of allergenic drugs.

In Vitro Assays in Severe Cutaneous Adverse Drug Reactions: Are They Still Research Tools or Diagnostic Tests Already?

Severe cutaneous adverse drug reactions (SCARs) represent life-threatening medical conditions and an appropriate causative diagnosis of these conditions is of the highest importance. Existing in vivo diagnostic methods are risky or are just contraindicated in these patients. Therefore, in vitro tests take on greater significance. In this survey, the studies on in vitro assays in SCARs were identified with a defined searching strategy and strict eligibility criteria. Different methods in the particular clinical manifestations and the groups of drugs were compared in respect to the diagnostic parameters obtained. The lymphocyte transformation test and IFNg-ELISpot (Interferon γ-Enzyme-linked immunospot assay) appeared to have the best evidence currently available. Further diagnostic assays, which are based mostly on distinct mechanisms of SCARs, may outdo previous assays but they still need confirmation in a larger group of patients and in more research centers. Data from pediatric populations and acute generalized exanthematous pustulosis (AGEP) patients are scarce. Some technical issues, limitations, and modifications of routine laboratory methods are also discussed.

Interleukin-4 and interferon-γ are possible allergic markers in pediatric patients with β-lactam hypersensitivity

Background:

β-lactam agents are known to elicit T-cell-mediated immune responses that play a central role in the onset of allergic reactions, but the involvement of specific type of cytokines in drug allergy remains largely unexplored in humans.

Objectives:

This study was undertaken to investigate the role of cytokines involvement in pediatric patients with β-lactam hypersensitivity and to determine whether involvement of cytokines in drug-mediated reactions are important for the perspective of allergic patient's management.

Methods:

β-lactam-induced hypersensitivity reactions in eighty pediatric patients were determined by clinical manifestations and skin prick or intradermal testing. Production of T-helper (Th) type-1 cytokine interferon (INF)-γ, Th-2 cytokine interleukin (IL)-4, regulatory T-cell cytokine IL-10, and other cytokines IL-6 and IL-12 were determined by sandwich ELISAs.

Results:

Diagnosis of β-lactam allergy was confirmed in 53 pediatric patients. IL-4 secretion in patients' sera was significantly higher as compared with healthy controls (P < 0.05). However, INF-γ level in patients' sera was significantly lower as compared with controls (P < 0.05). No significant alterations were found in the protein secretion of IL-10, IL-12, and IL-6 in allergic patients as compared with controls (P > 0.05).

Conclusion:

We conclude that IL-4 is specific marker for the diagnosis of β-lactam-induced hypersensitivity. Moreover, IL-4 in combination with INF-γ is more sensitive for the diagnosis of these reactions. This study also concludes that both IL-4 and INF-γ may play an active role in the onset of allergic reactions against β-lactam antibiotics.

The lymphocyte transformation test in allergic contact dermatitis: New opportunities

Allergic contact dermatitis (ACD) is driven by the activation and proliferation of allergen-specific memory T-lymphocytes and is currently diagnosed by patch testing with a selected panel of chemical allergens. The lymphocyte transformation test (LTT) can be used to monitor ex vivo T-lymphocyte responses to antigens, including contact allergens. The LTT is not viewed as being an alternative to patch testing, but it does seek to reflect experimentally skin sensitization to specific chemicals. The LTT is based on stimulation in vitro of antigen-driven T-lymphocyte proliferation. That is, exposure in culture of primed memory T-lymphocytes to the relevant antigen delivered in an appropriate configuration will provoke a secondary response that reflects the acquisition of skin sensitization. The technical aspects of this test and the utility of the approach for investigation of immune responses to contact allergens in humans are reviewed here, with particular emphasis on further development and refinement of the protocol. An important potential application is that it may provide a basis for characterizing those aspects of T-lymphocyte responses to contact allergens that have the greatest influence on skin sensitizing potency and this will be considered in some detail.

Differential cytokine and transcription factor expression in patients with allergic reactions to drugs

BACKGROUND

Allergic drug reactions (ADR) can be either immediate reaction (IR) (IgE mediated) or delayed reaction (DR) (T-cell mediated). They follow the Th1/Th2 paradigm, with DR expressing interferon-gamma (IFN-gamma) with down-regulation of interleukin-4 (IL-4) and IR expressing IL-4 with down-regulation of IFN-gamma. We studied the extension of this polarization in DR and IR by examining the cytokine and transcription factor profile in T-cell subpopulations during the acute phase of an ADR.

METHODS

Expressions of cytokines [IL-4, IFN-gamma and tumor necrosis factor-alpha (TNF-alpha)] and transcription factors (c-maf, GATA-3 and T-bet) were analysed by semi-quantitative real time-polymerase chain reaction in peripheral blood mononuclear cells and in CD4 and CD8 subpopulations from ADR patients.

RESULTS

In DR, IFN-gamma, TNF-alpha and T-bet increased significantly in both CD4 and CD8 subpopulations, depending on the clinical severity. In IR, IL-4, c-Maf and GATA-3 were increased, but only significantly in CD4. A positive correlation existed between IFN-gamma and T-bet in DR and between IL-4 and c-Maf and GATA-3 in IR. In DR, IFN-gamma, TNF-alpha and T-bet were increased during the acute phase in CD4 and CD8. In IR, IL-4, c-Maf and GATA-3 were all increased in the acute phase, but only in CD4.

CONCLUSIONS

These results support the Th1/Th2 paradigm in ADR, confirming previous findings that include the expression in both CD4 and CD8 T cells, and extending the observation to the transcription factors involved in the polarization of the immune response. Monitoring the reactions in the cell populations implicated, could be an important tool for assessing the mechanisms involved in ADR.

Nonimmediate reactions to systemic corticosteroids suggest an immunological mechanism

BACKGROUND

Administration of corticosteroids (CS) by different routes may cause varying types of allergic reactions, thereby hampering their further use in affected patients. In order to verify an immunological involvement we evaluated a group of patients with symptoms compatible with nonimmediate allergic reactions to CS.

METHODS

Studies included patch and intradermal tests, immunohistochemical studies and controlled administration to reproduce the response. The cytokines interleukin (IL)-4, interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha were quantified in peripheral blood during the response.

RESULTS

Of 32 subjects evaluated presenting nonimmediate urticaria or exanthema, 21 were finally considered positive after re-exposure. The drugs most frequently involved were betamethasone and dexamethasone. Fewer than half the patients responded to prednisolone whilst some responded to three or more CS. Hydrocortisone and deflazacort were well tolerated by all the patients. Subjects with a positive intradermal or patch test had a perivascular mononuclear cell infiltrate with the presence of CD4 and CD8 lymphocytes positive for CD45RO+ (memory) and CD69 (activation marker) cells. Monitoring peripheral blood during the acute response showed expression of IFN-gamma and TNF-alpha, with downregulation of IL-4.

CONCLUSION

Adverse systemic responses to different CS are suggestive of a nonimmediate reaction. The symptoms elicited together with the immunlogical studies suggest a T-cell mediated response. The response to closely related CS was especially marked between betamethasone and dexamethasone, whereas hydrocortisone and deflazacort were well tolerated.

Genetic aspects of immune-mediated adverse drug effects

Adverse drug effects (ADEs) are of great importance in medicine and account for up to 5% of all hospital admissions. ADEs can arise from several mechanisms and a wide range of drugs can cause immune-mediated ADEs (IMADEs). For a drug to elicit an IMADE, it must be both immunogenic (that is, able to sensitize the immune system) and antigenic (that is, able to evoke a response from a sensitized immune system). Unlike protein therapeutics, small-molecule drugs (or xenobiotics) are usually neither immunogenic nor antigenic. IMADEs are therefore the result of complex interactions between drug-metabolizing enzymes, immune sensitization and immune effectors. The genetic aspects of this interplay are discussed in this review.

Increased in Vitro Release of Interferon-Gamma from Ampicillin-Stimulated Peripheral Blood Mononuclear Cells in Stevens-Johnson Syndrome

Stevens-Johnson syndrome (SJS) was diagnosed in a 39-year-old woman, treated with ampicillin (4000-8000 mg daily), phenytoin (250 mg daily), and furosemide (20-40 mg daily) for 25, 21, and 20 d, respectively, before the appearance of the eruption. The lymphocyte stimulation test with the MTT [3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay on ampicillin, phenytoin, and furosemide showed a low value of stimulation index, which indicated negative reactivity. An in vitro IFN-gamma release test was conducted on the patient with SJS and on two healthy controls. IFN-gamma release increased by 52% following the in vitro challenge of the patient's peripheral blood mononuclear cells (PBMCs) with 15 microg/ml of ampicillin, but not with phenytoin or furosemide. Neither of the controls experienced increased IFN-gamma release. In the present case, increased in vitro IFN-gamma release was observed on ampicillin-stimulated PBMCs, which may indicate the role of ampicillin as the drug responsible for the induction of SJS, and may imply the role of IFN-gamma in the pathogenesis of SJS.

Gene polymorphisms within the immune system that may underlie drug allergy

Drug allergy encompasses a broad spectrum of different diseases. It occurs in some individuals, whereas it does not occur in many others. This suggests, among others, the involvement of hereditary factors, and thus of gene polymorphisms. Since drug metabolising enzymes as well as the immune system itself may be responsible for drug allergy, gene polymorphisms are relevant in both systems. While already some information exists on gene polymorphisms of drug metabolising enzymes that result in drug allergy, little information is available on gene polymorphisms within the immune system that result in such allergy. This review sets out to provide an avenue for future research aimed at discovering such polymorphisms. To this end, immune mechanisms that underlie drug allergy will be discussed. A pivotal mechanism underlying several types of drug allergy, immediate-type (type I) hypersensitivity, is also a hallmark of asthma, and therefore drug allergy and asthma share a range of candidate genes. Research on asthma has come relatively far in establishing associations of disease with polymorphisms in these genes. Therefore, these polymorphisms and their associations with asthma will be discussed. These studies on asthma provide us with lessons on how to conduct such studies on drug allergy.

Gene expression levels of cytokine profile and cytotoxic markers in non-immediate reactions to drugs

Drugs can induce IgE mediated or T cell dependent immunological reactions. T cell dependent reactions are poorly understood, although T lymphocytes have been proposed as a protagonist in a number of non-immediate immunological reactions (NIR). The objective was to study in vivo different regulatory and proinflammatory cytokines and cytotoxic markers in patients with NIR to drugs. Twenty patients with NIR after drug intake were classified into two groups: Group A (severe), Stevens-Johnson syndrome and toxic epidermal necrolysis; and Group B (mild), maculopapular exanthema and desquamative exanthema. Another 25 subjects taking the same drugs but without reactions formed a control group. Samples were obtained within 24 hours of the reaction and 30 days later. IL-2, IL-4, IFN, TNF, perforin, granzyme B (GrB), and FasL mRNA expression levels were determined in peripheral blood mononuclear cells by competitive RT-PCR. There were 9 patients in Group A and 11 in Group B. The drugs involved were betalactams (8), anticonvulsants (6), allopurinol (1), sulfamethoxazole (1), amiodarone (1) dypirone (2), and erythromicine+paracetamol (1). At the acute stage there was a high increase of IL-2, IFN, and TNF mRNA expression in both groups vs. controls, perforin and GrB varied in each group with patients in Group A having the highest values, and FasL was only expressed in Group A. Relationships between the cytokines were only significant in Group B (p < 0.05). Only the relation between IFN-gamma and TNF-alpha was significant in Group A. There was a significant correlation between cytotoxic markers in both groups (A: p < 0.001, B: p < 0.01). These data demonstrate the complexity of the Th1 phenotype in NIR after drug intake. In patients with mild NIR, cytokines appear to play a closely related role, whereas cytotoxic markers appear more relevant in severe reactions.

Determination of interleukin-5 secretion from drug-specific activated ex vivo peripheral blood mononuclear cells as a test system for the in vitro detection of drug sensitization

BACKGROUND

In vitro detection of drug sensitization is still limited. The lymphocyte transformation test, which determines drug-specific proliferation, is the only in vitro test for detecting drug sensitization at the cellular level irrespective of the reaction's clinical phenotype. Accumulation of eosinophils following IL-5 secretion from drug-specific stimulated T cells is a characteristic histological feature of drug-induced skin eruptions.

OBJECTIVE

We determined whether in vitro drug-specific activation of ex vivo peripheral blood mononuclear cells from 10 patients with drug-induced maculopapular exanthems and three patients with severe skin reactions results in secretion of IL-5, IL-10 or IFN-gamma and assessed the sensitivity and specificity of drug-specific IL-5 secretion as a test system compared with the lymphocyte transformation test and patch tests. Furthermore, the subsets of CD4+ and CD8+ T cells involved in drug-specific proliferation, IL-5 secretion and mRNA expression were examined in three patients.

METHODS

Drug-specific proliferation of peripheral blood mononuclear cells in the lymphocyte transformation test was investigated by 3H-thymidine uptake, and culture supernatants taken after 5 days were analysed for IL-5, IL-10 and IFN-gamma concentrations by ELISA technique. IL-5 mRNA expression was determined by RT-PCR.

RESULTS

Drug-specific activation of peripheral blood mononuclear cells consistently resulted in IL-5 and to a lesser extent in IL-10 and IFN-gamma secretion. The sensitivities of the patch test, lymphocyte transformation test and assessment of drug-specific IL-5 secretion for the detection of drug sensitization were 55%, 75% and 92%, respectively.

CONCLUSION

These data suggest a role for the determination of drug-specific IL-5 secretion by ex vivo peripheral blood mononuclear cells for the in vitro detection of drug-sensitization in drug-induced maculopapular exanthems.

Penicillin conjugates to interferon-gamma and reduces its activity: a novel drug-cytokine interaction

Beta-lactam antibiotics are the class of drug most frequently associated with IgE-mediated allergy but the mechanisms underlying this response are poorly understood. IFN-gamma is a key cytokine in immunity with regulatory actions on monocytes, NK cells, epithelial cells, and T and B lymphocytes. IFN-gamma promotes Th1 responses and inhibits Th2- and IgE-mediated responses. In this study we show, by Western blotting, that the prototype beta-lactam benzylpenicillin (BP) conjugates to human IFN-gamma but not to IL-4. The interaction of BP with IFN-gamma inhibited the cytokine's detection by immunoassay and impaired its activity, as assessed in three different assays: upregulation of MHC molecules on monocytes plus induction of nitric oxide synthesis and expression of monocyte chemoattractant protein-1 mRNA by epithelial cells. This is the first reported example of a direct drug-cytokine interaction and suggests a mechanism by which penicillin may disrupt IFN-gamma-dependent immune responses and promote allergy.

Drug metabolism, danger signals, and drug-induced hypersensitivity

One of the most difficult challenges for the practicing allergist/immunologist today is that of evaluating and managing patients who present with histories of drug-induced reactions. Adverse drug reactions are heterogeneous, and a single drug can often cause a multitude of reactions. Because the mechanisms responsible for many of these reactions are not known, they can be, and often are, difficult to classify. Moreover, for those that have features consistent with immune-mediated mechanisms, our diagnostic tools remain limited, because little is known about the relevant immunogenic determinants of most drugs. Despite these challenges, management approaches must be devised for patients who present with histories of drug-induced disease. Simply telling such a patient to avoid all drugs that have been associated with previous adverse events leaves both the patient and the referring physician frustrated. The initial part of this review focuses on exciting current research that is furthering our understanding of the mechanisms responsible for drug-induced reactions. Because it will take time to translate this new information into clinical practice, the latter part of the review focuses on ways to evaluate and manage patients who present with drug-induced reactions using the tools and the knowledge that are currently available.

Th(1)/Th(2) responses to drugs

T lymphocytes can be characterized by their pattern of cytokine secretion and be divided into type I (Th(l)/Tc(l)) and type 2 (Th(2)/Tc(2)) subsets. The involvement of type-1 or type 2-like responses in sensitization has been studied in the mouse, with reference contact and respiratory contact sensitizers. One interesting feature with certain drugs, such as beta-lactam antibiotics, is the diversity of clinical manifestations associated with immune-mediated hypersensitivity reactions in humans: immediate reactions such as urticaria, Quincke oedema and anaphylactic shock, and delayed hypersensitivity reactions, such as maculopapular rashes, allergic contact dermatitis and skin reactions of other types. In the mouse, Th(1) and Th(2) cytokines have been shown to regulate primary and secondary benzylpenicilloyl- (BPO-) specific antibody responses. Peripheral blood lymphocytes isolated from patients with a clear history of beta-lactam allergy were assessed for type-1 and type-2 phenotypes. Immediate reactions involved mixed Th(1), Tc(1), and Tc(2) responses, whereas allergic contact dermatitis involved Tc(1) and Th(1) cells. Other delayed hypersensitivity reactions to beta-lactams were restricted to Th(1) responses. It has been demonstrated that both CD4(+) and CD8(+)-lidocaine-specific T cell clones isolated from patients with allergic contact dermatitis produced IFN-gamma, even though CD8(+) clones only produce IFN-gamma, while IFN-gamma producing CD4(+) cells concomitantly produced IL-5 and IL-4. Together these data illustrate the heterogeneity of drug-specific T-cell responses.

In vitro drug allergy detection system incorporating human liver microsomes in chlorazepate-induced skin rash: drug-specific proliferation associated with interleukin-5 secretion

BACKGROUND

Chlorazepate is a benzodiazepine often used for pre-operative anxiolysis. The central metabolite responsible for the pharmacological and probably for the adverse effects of most benzodiazepines, including chlorazepate, is N-desmethyldiazepam. We report a woman who developed a generalized exanthem 1 day after receiving chlorazepate and four other drugs related to anaesthesia for surgery of the larynx. Patch tests pointed to chlorazepate as the culprit drug for the skin rash.

OBJECTIVES

The purpose of this study was to detect drug allergy to chlorazepate or a metabolite in vitro by means of the lymphocyte transformation test (LTT), and to determine the concentrations of the T-helper (Th) 2-type cytokine interleukin (IL)-5 and the Th1-type cytokine interferon (IFN) -gamma in the culture supernatants.

METHODS

We performed an LTT with peripheral blood mononuclear cells from the patient and a control, employing human liver microsomes containing cytochrome P450 enzymes as a metabolizing system, in parallel cultures. IL-5 and IFN-gamma concentrations in the culture supernatants were assessed by enzyme-linked immunosorbent assay.

RESULTS

In the LTT, no T-cell reactivity was observed to the parent compound chlorazepate, whereas coincubation of the drug with human liver microsomes yielded proliferative T-cell reactivity, which was associated with secretion of IL-5 but not of IFN-gamma.

CONCLUSIONS

We conclude that addition of a metabolizing system may be advantageous for in vitro detection of T-cell reactivity to drug metabolites in the LTT.