1. The antibody response of rabbits following intracutaneous injections of pneumococcus or of streptococcus vaccines showed three phases.
(a) Within 5 to 12 days following a single injection of pneumococcus or of streptococcus vaccine, high antibody titres were detected in extracts from the site of the injection into the skin, the spleen, the bone marrow, and the liver. Occasionally, antibodies were also found in the draining lymph nodes. During this first phase, the titre of the circulating antibodies was low or negative. (b) During the next phase, when the interval between antigen injection and antibody titrations was prolonged from 2 to 4 weeks, the titres of the blood and of the organs showed only slight differences. High titres were observed during this period in extracts from the injected parts of the skin. (c) After a still longer interval during a third phase of antibody response, the serum titre decreased more rapidly than the titre of the extracts from spleen, bone marrow, and injected skin.
2. Similar results were obtained in rabbits following repeated intracutaneous injections of the vaccines. In these rabbits, however, antibodies usually were not detected during the first phase in extracts from the site of the injection into the skin. The repeated injections of the antigen had perhaps neutralized locally formed antibodies and interfered with their detection until an excess of antibodies was produced. No antibodies were found in the lymph nodes of the rabbits that had received repeated injections of vaccines.
3. The antibody titre of the kidney, anterior wall of the stomach, and non-injected parts of the skin was negative or very low.
4. The demonstration of antibodies in extracts from the site of the injection of antigen into the skin and their presence in lymph nodes before they are demonstrable in the blood shows that they are formed at the local site of inflammation. At the same time antibodies are formed in organs that fix antigen, namely in spleen, liver, and bone marrow.