Antigen skin testing

Because of the risks of adverse reaction to the vaccine by persons who had already been exposed to the disease a sensitivity test must be carried out prior to immunization with BCG. A Mantoux skin test assesses an individual s sensitivity to a purified protein derivative (PPD) prepared fi om heat-treated antigens (tuberculin) extracted fiom M tuberculosis. A positive test imphes past infection or past, successful immunization Those with strongly positive tests may have active disease and should be referred to a chest clinic. Many people with active TB, especially disseminated TB, however, sero-convert fiom skin test positive to skin test negative. Results of the skin test must therefore be interpreted with care. 

Further assessment of atopy in the pathogenesis of the acute byssinotic reaction necessitates purification of well characterized and standardized cotton dust antigens, and the development of an allergy specific test (HAST) to measure serum IgE antibodies to cotton dust allergens. Such developments would allow correlation of skin tests, clinical history, dust exposure, FEVj and serum IgE level with specific IgE to cotton dust allergens. 

In addition to the flush, wheal, and flare, transient pain and itching result from the effects of histamine on sensory nerve endings. In sensitized individuals, intra-dermal injection of specific antigens produces a wheal this reaction is the basis for a skin test to quantify the extent of the allergic response. 

Does not identify those patients who react to a minor antigenic determinant (i.e., anaphylaxis) does not reliably predict the occurrence of late reactions patients with a negative skin test may still have allergic reactions to therapeutic penicillin... 

In order to study the immunostimulating effect of l-(chloromethyl)-3,7,10-trimethylsilatrane investigations were made of the weight coefficients of immunocompetent organs (thymus and spleen), the total leucocytes and erythrocytes in peripheral blood, titre of blood complement, the amount of antigen-reactive ro-sula-forming lymphocytes in spleen and thymus, microbial dissemination of skin as well as skin test with trypan blue. 

Park S, Ohya F, Yamashita K, et al Comparison of response to immunotherapy by intradermal skin test and antigen-specific IgE in canine atopy. J Vet Med Sci 2000 62 983-988. 

Mechanism It has been stated that in patients with penicillin-specific IgE antibodies who underwent successful penicillin desensitization, the data suggest that anti-specific, mast cell desensitization is responsible for the tolerant state and that mediator depletion plays no role (190). Additionally, the clinical observation that wheal-and-flare skin responses to penicillin often become negative with successful desensitization, while IgE responses to other antigens remain unchanged, also supports an involvement of an antigen-specific mechanism. Furthermore, both clinical reactivity and skin-test reactivity return within a few days, unless a tolerant state is maintained by continued drug administration. The author stressed that these findings show that the desensitized state depends on the... 

A 2-year-old child developed bronchospasm and cutaneous and laryngeal edema immediately after the injection of a 23-valent polysaccharide pneumococcal vaccine. The sjmptoms resolved within 1 hour of treatment with antihistamines, glucocorticoids, and aerosols. Skin tests and specific IgE tests showed that the pneumococcal antigens were responsible for the anaphylaxis. 

One hundred additional patients with hay fever were challenged with chamomile tea extract as a skin test and as a conjuctival provocation test to determine the prevalence of this type of reaction. IgE to chamomile tea was also measured. Only two of the 100 patients had a positive reaction to ocular chamomile tea extract. This ruled out an irritant effect of the tea as a mechanism of the patients responses, but clinicians must be aware that irritants such as alcohol may be present in chamomile products used in the eye. Twenty-eight patients had specific IgE to antigens contained in the chamomile tea extract (Subiza et al., 1990). 

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