Intradermal skin testing may often give inaccurate results because of poor stability of allergens and loss of protein by adsorption to the walls of containers and syringes during the process of making the extreme dilutions required with potent extracts. To test the ability of stabilizers to prevent such losses of allergenic activity, three diluents for allergens were compared: standard phosphate-buffered saline (PBS), pH 7.4, containing 0.4% phenol and the same buffer containing either 0.03% human serum albumin (HSA) or 0.005% Tween 80. Tenfold dilution series of ragweed, grass, Altemaria, and dust allergens were tested by the intradermal threshold dilution technique in the same group of patients five times over six months, comparing stored dilutions with dilutions freshly made from the same batches of lyophilized extracts. Results with Tween 80 and HSA buffers were identical and highly reproducible; however, each new set of dilutions in standard buffers frequently showed within 24 to 48 hr after preparation a lower skin test potency which varied unpredictably between ten and one thousandfold. Furthermore, upon prolonged storage at 4 °C, dilutions in standard buffer lost further activity. Storage of radiolabeled antigen E (AgE) in ordinary glass tubes for 24 hr showed adsorption of about 5% of the labeled protein to glass in the absence of stabilizers but only 0.5% in the presence of stabilizers. We conclude that stabilizing agents should be added to diluting fluids in preparing allergens for skin testing or immunotherapy.
ASJC Scopus subject areas
- Immunology and Allergy