Studies on Sensitization. III. Skin Sensitivity in the Absence of Serum Precipitins

Abstract

It is generally assumed that the tissue hypersensitiveness which follows repeated injections in rabbits of substances protein in nature, is accompanied by the presence of serum precipitins in these animals. Opie 1 claims that the local inflammatory response in sensitized animals is due to the meeting of the serum precipitin with the antigen in the tissues. In our studies, we have constantly found serum precipitins to accompany skin sensitivity in the early weeks of sensitization. But with time, especially after a lapse of several months following the initial sensitization of the rabbits, skin sensitivity is frequently present in the total absence of serum precipitins. The accompanying table gives an illustration of such findings.

Studies now in progress indicate that sensitization following injection of protein, frequently precedes by a few days the appearance of serum precipitins. Soon, the latter reach a high level—even up to 1:1,000,000 dilution, or higher—the skin sensitivity titer usually lagging. Shortly the serum precipitin titer begins to drop, gradually becoming negative. The skin sensitivity titer, however, remains at a fairly high level for many months. No data are available at present as to the length of time a rabbit will remain sensitized after the protein injections have been discontinued.