Contact sensitivity in the pig.

Following the application of a sensitizing dose of DNFB the afferent lymph draining the site becomes yellow due to the presence of dinitrophenylated proteins. Intralymphatic perfusion of such afferent lymph either whole or cell-free into recipients led to the development of contact sensitivity to DNFB in these animals. All of the OD, due to the DNP group, in the afferent lymph was precipitable with trichloracetic acid and at least 90 per cent non-dialysable. Preliminary data indicate that the DNP is conjugated to eight or more proteins; however, the chemical nature of the carrier(s) responsible for the induction of contact sensitivity and whether it is derived from interstitial fluid or skin are unknown. In a second group of experiments, conjugation of DNP to autologous lymph node cells and subsequent infusion via the afferent lymphatic, induced contact sensitivity against DNFB, and furthermore, very small amounts of DNP administered in this manner were required. In contrast 0.1 μmol of DNP coupled to RBCs did not induce contact sensitivity in five of six experiments. These results indicate that one mechanism leading to the induction of contact sensitivity to DNFB in the pig is by direct conjugation of this chemical to the specific carrier which subsequently passes to the regional lymph node via the afferent lymph. A second possible mechanism is that DNP at the peripheral site conjugates directly to WBCs which function as carriers. Although we as yet have no evidence that this second possibility occurs , it remains attractive because of the minute amounts of DNP which can induce contact sensitivity after coupling to lymph node cells .