Allergic reactions classification

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. 

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... 

It is classical to divide allergic reactions into four types according to the classification of Gells and Coombs (1962). Whereas this classification may still appear valid as far as some of the initial triggering events of allergic or immunologically mediated reactions are concerned, it has become obvious that it represents a rather simplistic approach to the complex reality of immunologically mediated reactions in tissues. 

Penicillins and cephalosporins are prototypes for allergic reactions of type I by the classification of Coombs and Gell (1963), based on the pathogenetic mechanisms. They are mostly IgE mediated. But type III and type IV reactions also occur. 

Coombs RRA, Gell PGH (1963) The classification of allergic reactions underlying disease. In Clinical aspects of immunology. Gell PGH, Coombs RRA (eds.) Blackwell Scientific, Oxford, pp 317-337... 

Table 2. Classification of allergic reactions to drugs according to the suspected immunologic mechanism...

The table established by Gell and Ccx)mbs is of importance when analyzing the type of immunologic reaction (Table 2). However, in this specific field of allergic reactions to drugs, there are several reactions which fail to enter into this practical but oversimplified classification. For instance ... 

Coombs and Gell (1963) have classified all immunologic (allergic) reactions into four types (I to IV). The classification of Types I to III depends on whether antigen or antibody is cell-fixed or in solution. Type IV is cell-mediated and is typified in the skin by responses such as the tuberculin reaction which develops macroscopically over 36-48 hr and lasts for 72-96 hours. This is the classical delayed hypersensitivity reaction. 

In the Gell and Coombs classification of allergic reactions, four types of hypersensitivities designated types I, n. III, and IV are distinguished. 

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