Hypersensitivity Classification

Hypersensitivity can be defined as an exaggerated response of the immune system leading to host tissue damage. However, some of the immune responses described in the hypersensitivity classification below are, in some circumstances, appropriate responses to invading antigen. For example, a component in what is an appropriate immune response to tissue transplant rejection can be defined as a type II hypersensitivity reaction. 

The antineoplastic dm are contraindicated in patients with leukopenia, thrombocytopenia, anemia, serious infections, serious renal disease, or known hypersensitivity to the drug and during pregnancy (see Display 55-1 for pregnancy classifications of selected antineoplastic drag s). 

Table 3. Grade of severity for quantification of immediate hypersensitivity reactions (according to the classification from the French Society for Anesthesiology)... 

Hypersensitivity reactions with P-lactam antibiotics, especially penicillin, may encompass any of the type I through IV Gell-Coombs classifications. The most common reactions are maculopapular and urticarial eruptions.7 While rare (less than 0.05%), anaphylaxis to penicillins causes the greatest concern because they are responsible for the majority of drug-induced anaphylaxis deaths in patients, accounting for 75% of all ana-i phylaxis cases in the United States.5,8 The treatment of ana-I phylaxis is given in Table 51-2.9... 

Coombs, R.R.A. and Gell, P.G.H. (1975). Classification of allergic reactions responsible for clinical hypersensitivity and disease. In Clinical Aspects of Immunology. (Gell, P.G.H., Coombs, R.R.A. and Lachman, D.J., Eds.). Blackwell Scientific Publications, Oxford, p. 761. 

Rajan TV. 2003. The Gell-Coombs classification of hypersensitivity reactions A reinterpretation. Trends Immunol. 24 376-379. 

The penicillins [pen i SILL in] are the most widely effective antibiotics and are among the least toxic drugs known the major adverse reaction to penicillins is hypersensitivity. The members of this family differ from one another in the R substituent attached to the 6-aminopenicillanic acid residue. The nature of this side chain affects their antimicrobial spectrum, stability to stomach acid, and susceptibility to bacterial degradative enzymes (P-lactamases). Figure 30.1 shows the main structural features of the penicillins. Figure 30.2 shows the classification of agents affecting cell wall synthesis. 

Classification of chemically induced hepatotoxicity is primarily based upon pattern of incidence and histopathological morphology. Intrinsic hepatotoxic drugs demonstrate a broad incidence, dose-response relationship and will usually give similar results in humans and experimental animals. The incidence of liver damage from idiosyncratic hepatotoxicants is limited to susceptible individuals and results from hypersensitivity reactions or unusual metabolic conversions that can occur due to polymorphisms in drug metabolism genes (see Chapters 11 and 13). 

TABLE 32.7. Gell and Coombs Classification of Hypersensitivity Reactions... 

Hypersensitivity reactions to parahens, generally of the delayed type and appearing as contact dermatitis, have been reported. However, given the widespread use of parabens as preservatives, such reactions are relatively uncommon the classification of parabens in some sources as high-rate sensitizers may be overstated. ... 

Haptens or prohaptens can induce type I to IV immune reactions (Gell and Coombs classification)9 IgE-mediated drug hypersensitivity (type I), IgG-mediated... 

However, there are times when the immune system acts in an exaggerated manner leading to tissue damage. This is referred to as hypersensitivity. In the classic Coombs and Cell classification system, there are four types of hypersensitivity reactions. The first three (types 1-3) are mediated by antibody (e.g., IgG, IgE). The fourth type (type 4) is mediated by antigen-specific T cells and is also known broadly as delayed-type hypersensitivity (DTH). It is delayed because the reaction appears hours to days after antigen crosses into the skin. Though often thought of as... 

Yet another classification system refers to the nature of the host s response to the causative agent. Some agents, referred to as intrinsic hepatotoxicants, will cause hepatotoxicity in most individuals of most species. In the case of idiosyncratic hepatotoxicants, where a chemical s toxic effects are a function of unusual susceptibility of the exposed individual, it may not be clear whether the lesion is a manifestation of the hepatotoxic properties of the substance in question or a manifestation of the individual s untoward response to the agent. This response may mean hypersensitivity (allergic) reactions or exaggerated responses to minor alterations in liver function. For example, anabolic or contraceptive steroids cause diminished biliary excretion (cholestasis) in most... 

On the basis of the highly influential Gell and Coombs classification scheme, there are four categories of hypersensitivity. 

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