Earlier studies have shown that the injection of antigenic material into the pad of the rabbit's foot is followed by the appearance of antibodies in the regional lymph node, in lymph coming from that node, and especially in the lymphocytes present in such efferent lymph. In the present work the fate of particulate antigenic material has been investigated during the period between its injection into the foot of the rabbit and the appearance of antibodies in the regional lymphatic tissue.
It has been found that soluble substance of the same immunologic specificity as the antigenic material injected can be identified in extracts of the injected tissue and of the regional lymph node, and in the efferent lymph from that node. The concentration of this soluble material falls off slowly in the injected tissue in the course of the few days following the injection. It falls off quickly in the extract of the lymph node and in the lymph itself, and its disappearance is succeeded by the appearance of antibody.
Evidence is presented that the immunologically active substance is derived from the injected antigenic material by a physiologic process, and this process is discussed as the means by which antigens, originally comprised in cells, are made available to the lymphocyte.
