DELAYED HYPERSENSITIVITY III. SP~.cmlc DESENSITIZATION OF GUINEA PIGS SENSITIZED TO PROTEIN

A general method for experimental induction in guinea pigs and man of the delayed hypersensitive state directed against protein antigens has been decribed previously (1). Sensitization follows a single intradermal injection of a small amount of antigen in the form of a washed immune precipitate. Provided the specific precipitation is carried out in the region of antibody excess, active antibody production is suppressed and no circulating antibody can be detected for 2 to 3 weeks after the delayed type of skin reactivity has appeared. If the sensitizing injection is suspended in adjuvant containing killed acid-fast bacteria, the delayed skin reactions to a given amount of antigen are larger than those seen when mycobacteria are excluded. The present studies were undertaken to determine the effects of a single injection of specific antigen on the subsequent skin reactivity of guinea pigs sensitized by this method. In this paper we have used the term desensitization, as have others in the past, to indicate loss of skin reactivity to a specific antigen. In the experiments to be reported it has been shown that guinea pigs sensitized to protein antigens can be completely and specifically desensitized by a single injection containing a sufficient amount of the corresponding antigen. In the following paper, the systemic effects of specific challenge are described (2).