The World Allergy Organization (WAO) 2003 defines drug allergy as “immune-mediated drug hypersensitivity reactions”, also known as hypersensitivity reactions. Drug hypersensitivity reactions account for 3.4% to 17.8% of adverse drug reactions (ADRs). The diagnosis of antituberculosis drug hypersensitivity reactions (allergic reactions) remains a challenge for clinical and laboratory workers in tuberculosis, and the gold standard remains the drug provocation test (DPT). However, the clinical risk of DPT is high and may cause death. While other specialists usually discontinue all possible allergenic drugs in the event of a drug hypersensitivity reaction, TB treatment usually uses a multidrug combination regimen, and discontinuing all previously used drugs in the event of a drug hypersensitivity reaction may make effective TB treatment extremely difficult due to the limited availability of highly effective anti-TB drugs. Therefore, the search for an accurate and safe in vitro test for drug hypersensitivity reactions has been the goal of both TB clinicians and laboratory workers. To find an accurate and safe in vitro drug hypersensitivity test, we must have a clear understanding of the mechanism of hypersensitivity reactions. Drug hypersensitivity reactions belong to the category of specific immune reactions, which are essentially abnormal or pathologically specific immune reactions. Hypersensitivity reactions are recognized as four types, but there are also opinions that they are divided into six types. Type I hypersensitivity reactions are mediated by Ig E antibodies without complement involvement. It includes the sensitization phase in which Ig E antibodies are generated, transferred and bound to target cells, and the sensitization phase in which the same antigen re-enters the body and specifically binds to Ig E on the surface of mast cells or eosinophil membranes. The clinical manifestations are anaphylaxis, urticaria and neurovascular edema in drug dermatitis, gastrointestinal allergy, and respiratory allergic reaction. Because type I hypersensitivity reactions other than anaphylaxis are not as rapid and persistent as anaphylaxis, they are also referred to as type I hypersensitivity inflammation or persistent type I hypersensitivity reactions, and antihistamines work well in such patients. Recently, McNeil et al. showed that mast cells are the main effector cells in allergic reactions and play an important role in various inflammatory responses and immunomodulator-related diseases by secreting histamine. contraction. This led to the identification of Mrgprb2 as a target for the discovery and treatment of allergic reactions. Type II hypersensitivity reactions are also known as cytolytic or cytotoxic hypersensitivity reactions. The antibodies involved are mainly Ig G and, to a lesser extent, Ig M. These antibodies, when bound to surface antigens of the target cells themselves or to semi-antigens adsorbed on the membrane surface, or to antigen-antibody complexes adsorbed on the surface of the target cells, can damage the target cells in three different ways: 1) activation of complement, causing target cell lysis; 2) phagocytosis and lysis of the target cells by mononuclear phagocytes; and 3) by killer lymphocytes ( The Fc receptor of killer lymphocyte (abbreviated as “K cells”) binds specifically to the Fc segment of antibody on the surface of target cells, activating the K cells and then destroying the target cells. The main clinical manifestation is the damage and lysis of blood cells. Some scholars include hypersensitivity reactions of the K-cell pathway as type VI hypersensitivity reactions, also known as antibody-dependent cytotoxic reactions. Antibodies to certain anti-cellular components act directly on the cell to stimulate enhanced metabolic function and hypersecretion of that cell without destroying the target cells, such as allergic hyperthyroidism; some scholars include this type in type V hypersensitivity reactions, also known as stimulated hypersensitivity reactions. Type III hypersensitivity reaction is also known as immune complex type hypersensitivity reaction. Under certain conditions, soluble antigen-antibody immune complexes are deposited in the vessel wall, activating complement, attracting neutrophils to phagocytose immune complexes and releasing lysosomal enzymes, causing vasculitis and leading to systemic or local inflammatory reactions. Clinical manifestations include serum sickness, glomerulonephritis, rheumatoid arthritis, endogenous asthma, allergic alveolitis, and other immune complex disorders (e.g., allergic liver injury). Type IV hypersensitivity reactions are also known as delayed hypersensitivity reactions. In response to stimulation by certain antigens, T lymphocytes are sensitized and proliferate. When exposed to the same antigen again, the sensitized lymphocytes proliferate and directly kill the specific allergens or destroy the cells with the allergens. The main clinical manifestations are infectious allergic reaction, contact dermatitis (manifested by local redness, swelling, hard nodules, blistering and even exfoliative dermatitis), and transplant rejection. From the above mechanism, it can be seen that type I, II and III hypersensitivity reactions are mainly humoral immune reactions mediated by B lymphocytes or B lymphocytes combined with helper T cells (Th cells) type 2 CD4 T lymphocytes. Some allergens can also cause different types of hypersensitivity reactions at the same time or sequentially in the same individual. In the specific immune response there are immune memory cells (long-lived lymphocytes) and effector lymphocytes (short-lived lymphocytes). Immune memory cells include memory B cells and memory T lymphocytes; effector lymphocytes include plasma cells (PC) and effector T lymphocytes. Memory T lymphocytes are subdivided into central memory T lymphocytes (present in lymphoid organs, mainly CD4 T lymphocytes) and peripheral memory T lymphocytes (present in peripheral tissues and peripheral blood, mainly CD8 T lymphocytes). Upon re-exposure to antigen, memory lymphocytes are first stimulated, and memory lymphocytes play an immunomodulatory role, leading to mobilization of lymphocytes, proliferation and conversion of peripheral lymphocytes into effector lymphocytes, and immune response to the specific antigen. Advances in laboratory diagnostic techniques for antituberculosis drug hypersensitivity reactions It has been the endeavor of tuberculosis practitioners to explore safe and effective in vitro methods for drug hypersensitivity reactions. Research on laboratory diagnostic techniques for drug hypersensitivity reactions continues to progress, but no definitive method has been developed for clinical application. Clinical reliance on drug provocation tests remains. The progress of laboratory research is summarized as follows: I. Non-specific antibody detection Immunoglobulins Ig E, Ig G, Ig M, Ig A and complement are important components of the humoral immune response. and immune complexes, and this type of hypersensitivity reaction definitely requires the participation of complement. Therefore, antibody Ig E, Ig G, Ig M, Ig A and complement tests, especially the comparison of test results before and after the onset of hypersensitivity reactions, are useful for the diagnosis and differential diagnosis of type I, II and III hypersensitivity reactions [4-5,11-13]. However, most patients did not undergo Ig E, Ig G, Ig M, Ig A and complement testing before the occurrence of hypersensitivity reactions, and although the one-time test results have some reference significance, the clinical significance is relatively limited. Porebski et al. concluded that the detection of cytotoxic molecules granzyme B, granulysin, CD107a, CD69 cell surface activation marker molecules, lymphokines [interleukin (IL)-2, IL-5, IL-13 and γ-interferon-γ (Interferon-γ) γ,IFN-γ)] were evaluated to facilitate the determination of allergic reactions. According to the general principle of immune response, comparative analysis of test data before and after the appearance of hypersensitivity reactions is more meaningful, especially the analysis of cytokines generated from isolated lymphocytes for in vitro specific drug stimulation tests may have diagnostic significance. Third, specific anti-drug antibodies and complement assays have been found to have the presence of many specific anti-drug antibodies in the human body. Anti-drug antibodies can be used in drug immunoassays, as specific antagonists of toxins, drugs, hormones and as tools for drug research. The presence of specific anti-drug antibodies does not always lead to hypersensitivity reactions, and complement and related immune complex tests are required. The author proposed in 2001 that the early and safe diagnosis of type I, II and III hypersensitivity reactions is pending the development of in vitro detection reagents for specific anti-drug antibodies. However, due to the lack of awareness of antibody detection methodology among clinicians and the lack of attention to this area by laboratory personnel, no studies on the use of specific anti-tuberculosis drug antibody assays for the diagnosis of anti-tuberculosis drug hypersensitivity reactions have been reported so far. Drug-induced lymphocyte stimulation test (DLST), or lymphocyte transformation test (LTT), is a test that stimulates the proliferation of lymphocytes (including B and T lymphocytes) with drugs. The lymphocyte transformation test (LTT) is one of the methods to determine the in vitro safety of drug antigens causing hypersensitivity reactions by stimulating isolated peripheral blood lymphocytes (mainly B and T lymphocytes) and observing lymphocyte proliferation index. The current domestic and international literature on drug-stimulated lymphocyte proliferation assays reports mostly small sample numbers and lack of multicenter prospective studies, and although the reported specificity is good, the sensitivity is low, and the use of radioactive [3H]thymidine labeled lymphocytes has hidden risks of radioactive storage and disposal, which is not conducive to the promotion of clinical applications. Non-radioactive alternatives are also needed. Some drug-stimulated lymphocyte proliferation assays performed in the literature use single nucleated cells isolated from peripheral blood, but assume that only T lymphocytes are proliferating, which is inaccurate. In fact, under specific hypersensitivity antigen drug stimulation, not only memory T lymphocytes can regulate T lymphocyte proliferation and conversion to specific effector T lymphocytes, but also memory B lymphocytes and Th2 type T lymphocytes can regulate B lymphocyte proliferation and conversion to specific effector B lymphocytes (plasma cells) [4-5,24-26]. From the aforementioned mechanism of hypersensitivity reaction occurrence, the drug-stimulated lymphocyte proliferation test covers hypersensitivity reactions mediated by B and T cells, which means that it is applicable to the detection of all types of hypersensitivity reactions and should be more sensitive. The low sensitivity that has been reported in some studies may also be related to the imperfect research methods. For example, the determination of the results of the drug provocation test cannot be determined as hypersensitivity reactions only by the reproduction of adverse reactions, but should also be combined with other immunological test parameters and the relevant test results of toxic reactions except for the possibility of drug toxic reactions, which needs further improvement. On the other hand, because of its wide applicability, the inability to distinguish between types of hypersensitivity reactions is its drawback, and other immunological assays are needed to complement it. V. Specific plasma cell assay Mainly to detect drug-induced specific humoral immune response, isolate peripheral blood single nucleus cells, add drug-stimulated culture, and detect specific plasma cells by labeling plasma cells. Some scholars have used enzyme-linked immunospot technique (ELISPOT) to detect antibody-secreting plasma cell counts upon antigen stimulation [25], and flow cytometry to detect resting B cells (CD27-CD38-), memory B cells (CD27+CD38-), and plasma cell precursors ( CD27+CD38+) and plasma cells (CD27-CD38+) [26]. These same techniques can be used for the detection and determination of allergic drug antigens for antibody immune response types. VI. Specific T lymphocyte assay Primarily, drug-induced specific T lymphocyte immune responses are detected by isolating peripheral blood individual nuclear cells, adding them to drug-stimulated cultures, and detecting specific lymphocytes by labeling T lymphocytes. The T-cell spot test for tuberculosis infection (T-SPOT. TB) has been used for the diagnosis of latent tuberculosis infection. In fact, the release of IFN-γ from T lymphocytes has been associated not only with Mycobacterium tuberculosis infection but also with other infectious and inflammatory diseases and even tumors, and studies related to the detection of many other infections such as staphylococcus, malaria, toxoplasma, and viruses using the ELISPOT method have been reported [29-35]. When the specific stimulatory antigens, early secretory protein 6 (ESAT-6) and culture filtrate protein-10 (CFP10) of Mycobacterium tuberculosis, are replaced with specific antigens of other pathogenic organisms or specific drug antigens of allergy in T-SPOT.TB, they may also be used for other infectious diseases or drug allergens It should be used for the detection and diagnosis of hypersensitivity reactions to anti-tuberculosis drugs. Allergy-related genetic testing Drug hypersensitivity reactions are related to patient specificity and patient genotype. Drug hypersensitivity reaction syndrome (DIHS) is a severe systemic drug reaction characterized by acute extensive skin damage with fever, lymph node enlargement, multi-organ involvement, eosinophilia and mononucleosis, and hematological abnormalities. It is an immune allergic reaction triggered by drug and virus reactivation. In recent years, significant progress has been made in immunopathological and pharmacogenetic studies of immune-mediated severe adverse drug reactions, such as T-cell-mediated Stevens-Johnson syndrome, epidermolysis bullosa dermatitis, drug allergic liver injury, and other drug allergic syndromes, which have been shown to be associated with different human histocompatibility antigens also called leukocyte antigens (HLA) class I and class II molecules (including HLA-B*15-related antigens) mediated The human G protein-coupled receptor MRGPRX2 is the target of many small molecule drugs associated with allergic reactions. To date, no relevant studies on different anti-TB drug allergy-related gene fragments and loci have been reported, and genetic studies related to anti-TB drugs are recommended. Outlook In summary, laboratory tests used for drug hypersensitivity reactions are relatively numerous, including non-specific antibody assays, relevant cytokine assays, specific anti-drug antibody assays, lymphocyte transformation assays, specific plasma cell assays, specific T-lymphocyte assays, allergy-related gene assays, and other methods. The main problem at present is that the TB community has not paid enough attention to the integration and introduction of modern technologies, and the entire TB community, including those engaged in basic TB research, applied laboratory researchers, clinical TB diagnosis and treatment researchers, and TB control managers, needs to work together. In particular, specific drug-resistant antibody assays, specific plasma cell assays, specific T-lymphocyte assays, and genetic studies of anti-tuberculosis drug allergy deserve our in-depth exploration. We should embark on systematic, basic and clinically applied multicenter studies. By objectively analyzing the current situation and finding the right research direction, we believe that in the near future we can find the best method for in vitro testing of antituberculosis drug hypersensitivity and form a new safe gold standard for diagnosing antituberculosis drug hypersensitivity.