Search

Background Delayed-type β-lactam hypersensitivity develops in subset of patients. The cellular immunological processes that underlie the drug-specific response have been described; however, little is known about involvement of the humoral immune system. Thus, the aim of this study was to utilize piperacillin hypersensitivity as an exemplar to (i) develop cell culture methods for the detection of drug-specific B-cell responses, (ii) characterize drug-specific IgG subtypes and (iii) assess reactivity of IgG antibodies against proteins modified to different levels with piperacillin haptens. Methods IgG secretion and CD19+ CD27+ expression on B cells were measured using ELISPOT and flow cytometry, respectively. A piperacillin- BSA adduct was used as an antigen in ELISA antibody binding studies. Adducts generated using different ratios of drug to protein were used to determine the degree of conjugation required to detect IgG binding. Results B cells from hypersensitive patients, but not controls, were stimulated to secrete IgG and increase CD27 expression when cultured with soluble piperacillin. A piperacillin- BSA adduct with cyclized and hydrolysed forms of the hapten bound to eight lysine residues was used to detect hapten-specific IgG 1-4 subclasses in patient plasma. Hapten inhibition and the use of structurally unrelated hapten- BSA adducts confirmed antigen specificity. Antibody binding was detected with antigens generated at piperacillin/ BSA ratios of 10:1 and above, which corresponded to a minimum epitope density of 1 for antibody binding. Conclusion These data show that antigen-specific B lymphocytes and T lymphocytes are activated in piperacillin-hypersensitive patients. Further work is needed to define the role different IgG subtypes play in regulating the iatrogenic disease. [ABSTRACT FROM AUTHOR]

Drug hypersensitivity reactions ( DHRs) are a matter of great concern, both for outpatient and in hospital care. The evaluation of these patients is complex, because in vivo tests have a suboptimal sensitivity and can be time-consuming, expensive and potentially risky, especially drug provocation tests. There are several currently available in vitro methods that can be classified into two main groups: those that help to characterize the active phase of the reaction and those that help to identify the culprit drug. The utility of these in vitro methods depends on the mechanisms involved, meaning that they cannot be used for the evaluation of all types of DHRs. Moreover, their effectiveness has not been defined by a consensus agreement between experts in the field. Thus, the European Network on Drug Allergy and Drug Allergy Interest Group of the European Academy of Allergy and Clinical Immunology has organized a task force to provide data and recommendations regarding the available in vitro methods for DHR diagnosis. We have found that although there are many in vitro tests, few of them can be given a recommendation of grade B or above mainly because there is a lack of well-controlled studies, most information comes from small studies with few subjects and results are not always confirmed in later studies. Therefore, it is necessary to validate the currently available in vitro tests in a large series of well-characterized patients with DHR and to develop new tests for diagnosis. [ABSTRACT FROM AUTHOR]

Background For certain HLA allele-associated drug hypersensitivity reactions, the parent drug has been shown to associate directly with the risk allele. In other forms of hypersensitivity, HLA risk alleles have not been identified and T cells are activated in an allele unrestricted manner. Chemically reactive drug metabolites bind to multiple proteins; thus, it is assumed that the derived peptide antigens interact with a number of HLA molecules to activate T cells; however, HLA restriction of the drug metabolite-specific T-cell response has not been studied. Objective To utilize T cells from sulfamethoxazole ( SMX) hypersensitive patients with cystic fibrosis to examine the HLA molecules that interact with nitroso SMX ( SMX-NO)-derived antigens. Methods T-cell clones were generated from 4 hypersensitive patients. Drug-specific proliferative responses and cytokine secretion were measured. Anti-human class I and class II antibodies were used to analyse HLA restriction. Antigen-presenting cells expressing different HLA molecules were used to determine the alleles involved in the presentation of SMX-NO-derived antigens to T cells. Results A total of 976 clones were tested for SMX-NO reactivity. Thirty-nine CD4+ clones were activated with SMX-NO and found to proliferate and secrete cytokines. The SMX-NO-specific response was blocked with an antibody against HLA-DQ. SMX-NO-specific responses were detected with antigen-presenting cells expressing HLA-DQB1*05:01 (patient 1) and HLA-DQB1*02:01 (patient 2), but not other HLA-DQB1 alleles. Conclusion and Clinical Relevance HLA-DQ plays an important role in the activation of SMX-NO-specific CD4+ T cells. Detection of HLA-DQ allele-restricted responses suggests that T cells are activated by a limited repertoire of SMX-NO-modified peptides. [ABSTRACT FROM AUTHOR]