In vitro released interferon-gamma in the diagnosis of drug-induced anaphylaxis

ARTICLE

The diagnosis of anaphylactic shock reactions to drugs remains difficult. The oral provocation test has the best sensitivity, but the test itself may sometimes harm the patient. Therefore, there is a great need to develop a new in vitro method to make an accurate and reliable diagnosis of anaphylactic shock reactions to drugs. We previously reported that an in vitro drug-induced interferon-gamma (IFN-gamma) production test might be useful as a diagnostic tool for drug eruptions [1, 2]. In this paper we describe a case with drug-induced anaphylaxis, whose causative drug was determined by an IFN-gamma production test.

Case and methods

A 17-year-old male was first seen at our hospital in December 1997 with a 20-day history of frequent wheal, cutaneous or mucosal angioedema, and abdominal pain. He had no significant past medical history and he specifically had a negative atopic history. The results of the laboratory tests were within the normal limits; total IgE 87I U/ml (normal ¾ 400), C1 esterase inhibitor activity 101% (normal 80-125). Various oral antihistaminic drugs were thus administered under the diagnosis of chronic urticaria. However, new wheals, angioedema, and abdominal pain continued to appear, and these symptoms also tended to become particularly exacerbated in the evening. Ten days after his first visit, he developed a headache, general malaise and a high grade fever. In the evening he took 1 g of PL^® (salicylamide, acetaminophen, anhydrous caffeine and promethazine methylene disalicylate) and 2 tablets of Bufferin^® (aspirin and dialminate). Two hours later, cutaneous and mucosal angioedema, dyspnea, abdominal cramping and hypotension appeared and together caused the patient fall into anaphylactic shock. Intravenous steroid infusion and oxygen inhalation were administered and he successfully recovered several hours later. During the next two months, the chronic urticaria was controlled by antihistamic drugs.

We thereafter performed the prick test, patch test [3], drug-induced lymphocyte stimulation test (DLST)[3] and drug-induced IFN-gamma production test (IFN-gamma test), which have all been described previously [1, 2]. The IFN-gamma test was carried out by measuring the IFN-gamma activity in the culture supernatant obtained after the incubation of peripheral lymphocytes either with or without the causative drug. Each drug was broken into pieces by supersonic waves in sterile conditions and dissolved into RPMI medium. The patient's peripheral blood mononuclear cells (PBMC) obtained by Conray-Ficoll densimetric centrifugation were suspended in an RPMI medium with 10% fetal calf serum (1 x 10⁶/ml). PBMC were cultured in triplicate culture wells with or without PL^® (15 µg/ml), Bufferin^® (8 µg/ml) for 72 hrs at 37° C in a humidified atmosphere containing 5% CO₂. After 72 hrs, cell-free supernatants from triplicate culture wells were thus collected together and stored at ­ 70° C until used. The activity of IFN-gamma in the culture supernatant was measured with an EIA test kit (Medgenix diagnostics, Fleurus, Belgium). Three healthy subjects with a history of exposure to PL^® served as control sources of PBMC.

Results and discussion

The results of prick tests, patch tests and DLST carried out with PL^® and Bufferin^® were all negative. When PBMC from our patient were incubated with Bufferin^®, no significant differences were observed between the supernatants with and without the drug. When the PBMC were incubated with PL^®, however, a significantly high level of IFN-gamma was detected in the PBMC from our patient, while only a very slight level was seen in the control subjects (Table I). These results indicate that PL^® may thus have been the causative drug for anaphylactic shock in our case.

However, there is a possibility of a pseudoallergic reaction or an aggravation of symptoms in our patient with chronic urticaria. The clinical symptoms of a pseudoallergy often resemble the immediate-type hypersensitivity reaction and it is a well-known fact that the intake of NSAIDs (nonsteroidal anti-inflammatory drugs) such as PL^® and Bufferin^® aggravates the symptoms of urticaria. The pathogenesis of hypersensitivity of NSAIDs has yet to be clearly elucidated, but in pseudoallergy, no antigen-specific immune mechanism is involved. Our case indicates an antigen-specific immune mechanism because IFN-gamma was released by PBMC from the patient in response to stimulation with PL^®.

Generally, an in vitro IFN-gamma test may be useful in the diagnosis of a delayed-type hypersensitivity (DTH) reaction to drugs, because IFN-gamma is regarded as important in the effector phase of DTH [4], which is the Th1-mediated response. In this case, the prick test, patch test and DLST with PL^® and Bufferin^® were all negative, while only the IFN-gamma test with PL^® was positive. The in vitro IFN-gamma production, induced after stimulation with the causative drug, was also observed in our patient who demonstrated an anaphylactic shock reaction, which is generally regarded to be a Th2-mediated response. This finding may indicate the presence of drug-specific IFN-gamma producing T cells in patients with an anaphylactic shock reaction to medication. The polarization of the immune response (Th1 or Th2) is not absolute [5, 6], so varying numbers of drug-specific IFN-gamma producing, Th1 cells may thus be present in Th2-mediated anaphylaxis. Human Th2 cells have been reported to retain the ability to produce IFN-gamma when adequately stimulated [7], therefore in anaphylaxis drug specific Th2 cells may produce IFN-gamma on stimulation with the drug in vitro. As mentioned above, the Th1/Th2 dichotomy is less absolute in human than in mouse T cells, there is the possibility that Th2 cells may produce IFN-gamma or only Th1 cells can produce IFN-gamma. It is unclear which type of Th cell produced IFN-gamma in our case because we did not investigate other cytokines. The mechanism by which IFN-gamma is involved in anaphylaxis is not known. One possibility is that the imbalance between other cytokines may indirectly induce anaphylaxis. However, further study will be needed to clarify the exact mechanism.

In fact, the positive rate is very low for either the skin test or DLST when diagnosing hypersensitivity to drugs, and false-negative reactions are thus unavoidable in clinical practice. Assays that measure the drug-induced IFN-gamma production may thus be a useful diagnostic tool not only for identifying DTH to drugs, but also for predicting anaphylactic shock reaction to drugs.

REFERENCES

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