Eosinophils in Delayed Hypersensitivity Skin Reaction Sites

Guinea pigs immunized with egg albumin or an azobenzene arsanate conjugate of acetyl-tyrosine (ABA-tyr) in complete or incomplete Freund's adjuvant can develop eosinophil-containing delayed hypersensitivity skin reactions when challenged with specific antigen. Retest, achieved by the re-injection of antigen at the site of a prior skin test, leads to an accelerated reaction which may contain increased numbers of eosinophils. ABA-tyr which induces delayed hypersensitivity without antibody formation, dissociates the two components of the retest reaction; that antigen leads to an accelerated reaction, but one with only small numbers of eosinophils.