T cell-mediated drug hypersensitivity

Different Types of T Cell-Mediated Drug Hypersensitivity Reactions. 41... 

Beeler A, Pichler W. In vitro tests of T cell-mediated drng hypersensitivity. In Drug Hypersensitivity, edited by Pichler WJ, pp. 380-390. Basel Karger, 2007. 

The most common clinical picture of non-immediate RCM reactions is a macu-lopapular exanthema, which resembles other drug-induced T-cell-mediated hypersensitivity reactions. The reported onset of skin eruptions 2-10 days after the first exposure to a RCM and 1-2 days after re-exposure to the same substance is typical for an allergic drug reaction with a sensitization phase. 

Type IV Delayed-type Hypersensitivity (DTH). Delayed-type hypersensitivity reactions are T-cell mediated with no involvement of antibodies. However, these reactions are controlled through accessory cells, suppressor T cells, and monokine-secreting macrophages, which regulate the proliferation and differentiation of T cells. The most frequent form of DTH manifests itself as contact dermatitis. The drug or metabolite binds to a protein in the skin or the Langerhans cell membrane... 

Levamisole was first synthesized for the treatment of parasitic infections. Later studies suggested that it increases the magnitude of delayed hypersensitivity or T cell-mediated immunity in humans. In immunodeficiency associated with Hodgkin s disease, levamisole has been noted to increase the number of T cells in vitro and to enhance skin test reactivity. Levamisole has also been widely tested in rheumatoid arthritis and found to have some efficacy. However, it has induced severe agranulocytosis (mainly in HLA-B27-positive patients), which required discontinuation of its use. The drug may also potentiate the action of fluorouracil (5-FU) in adjuvant therapy of colorectal cancer, and this combination has been approved for clinical use in the treatment of Dukes class C colorectal cancer after surgery. Its use in these cases reduces recurrences, and the mechanism... 

The second most frequent drug allergy is the T cell-mediated hypersensitivity. Chemicals that come in contact with the skin can induce contact hypersensitivity reactions. Hapten-specific T cells are guided to the site of allergen contact, most probably due to continued or subsequent exposure of the site to the allergen,10 and result in immune-mediated skin reactions through the release of, for example, cytokines or chemokines. 

Risk factors for a late skin reaction following administration of an iodinated contrast medium include current and up to 2 years past treatment with interleukin-2 (IL-2), a history of drug allergy or contact hypersensitivity, and a history of reaction to a previous contrast medium. Late reactions are more conunon in patients who reacted previously, especially if the same contrast medium is administered (see below). The latter fact is interesting since it suggests that the mechanism of the late reaction with its demonstration of memory may be immunologically and, in particular, T cell mediated. 

The adaptive immune system is responsible for the occurrence of drug allergies after applying certain chemicals for example to the skin. Symptoms of such allergic hypersensitivities are observed only in the elicitation phase and not in the preceding sensitization phase, as only the second exposure to the causative drug results in T cell- or antibody-mediated adverse effects. 

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