Hypersensitivity testing, test methods

Tuberculin skin testing is an important part of the care of all HIV-1-infected patients or persons at risk for HIV-1 infection. Tuberculin skin testing should be done using the Mantoux method. A tuberculin reaction of >5 mm of induration is classified as positive in persons known to have or suspected of having HIV-1 infection. Unfortunately, as the CD4 lymphocyte count declines with progression of HIV-1 disease, many patients no longer react to delayed-type hypersensitivity testing. More than 60% of persons with CD4 lymphocyte counts of <200 cells/pl may have skin test reactions of <5 mm. Thus, it is impossible to detect the presence of tuberculous infection in many HIV-l-infected individuals. 

Sailstad, D. M. Murine local lymph node assay An alternative test method for skin hypersensitivity testing. Lab. Animal 31 36-41, 2002. 

Given the absence of routinely-used animal and in vitro test methods, most and in some cases perhaps all of the information available for an evaluation of the potential of a chemical to cause respiratory hypersensitivity is based on clinical and epidemiological findings in people exposed at the workplace or, occasionally,... 

However, this is still considered as open to question by some authors (Dewd-NEY 1977) who point out that the BPO determinant may appear predominant only because the testing methods mostly used for detection of penicillin hypersensitivity (skin and serological tests) appear to be most sensitive for this type of determinant. 

The guinea pig maximization test (GPMT) is a preferred method for the detection of skin sensitizers. It belongs to the class of adjuvant-tests, where the substance will be applied in Freund s complete adjuvant (FCA). The test is based on the possible induction of an immune response of the skin during an induction period (at least 1 week). This pretreatment of the subject will eventually result in a hypersensitive reaction during a further exposure, the so-called challenging phase. 

Gad SC, Dunn BJ, Gavigan FA et al. (1987) Development, validation, and transfer of a new test system technology in toxicology. In Goldberg AM (ed) New Test System in Toxicology. Mary Ann Liebert, New York, pp 275-292 Van Loveren H, Kato K, Ratzlaff RE et al. (1984) Use of micrometers and calipers to measure various components of delayed-type hypersensitivity ear swelling reactions in mice. J Immunol Methods 67 311-319... 

There are several acceptable ways to evaluate DTH responses in nonclinical species. Of these, the most common are the guinea pig assays used to assess contact sensitization. Both the Magnusson and Kligman model (guinea pig maximization test) and the Buehler model measure the elicitation phase of the hypersensitivity response, though the tests vary in their methods of chemical application and utilization of adjuvants. Most recently, the local lymph node assay has been accepted as a stand alone test for chemical hypersensitivity. This assay is conducted in mice and measures the induction phase of sensitization. In humans, the most common methods to assess delayed hypersensitivity are the patch test (contact sensitivity for diagnostic purposes) and the human repeat insult patch test (contact sensitivity for predictive purposes). Additionally, intradermal... 

Hypersensitivity and immunosuppression are considered the primary focus for developing in vitro methods in immunotoxicology. Nevertheless, in vitro assays to detect immunostimula-tion and autoimmunity are also needed. Although developmental immunotoxicity is an emerging concern, there are no in vitro test models available at this time. 

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