Inhibition of allergic reactions due to competition for mast cell sensitization sites by two reagins.

The ability of unrelated or incidental reagin to interfere competitively with mast cell sensitization by specific reagin has been examined using an experimental system whereby rats are induced to produce high levels of reaginic (IgE) antibody to two antigens. It is shown that passive sensitization by a reaginic antibody is inhibited (a) by simultaneous injection with a second reagin directed against another antigen, the degree of inhibition being related directly to the dose of the second serum or (b) if the test animal is actively producing unrelated reagin. The skin test sensitivity of rats actively producing high levels of two reagins as opposed to only one is also discussed. The results are presented with particular reference to the interpretation of PCA and other skin tests and to the possible importance of interference effects in multiple allergies.