Lymph node involvement in a humoral immune response

Mice were primed subcutaneously in the hind footpads with horseradish peroxidase (HRP) and boosted intravenously 10 weeks later. The appearance of cells with cytoplasmic anti‐HRP antibody was studied in several lymph nodes. It appeared that following intravenous boosting antibody‐forming cells appeared in significant numbers in the popliteal, the lumbar, and (in some animals) the sciatic lymph nodes exclusively. In the other lymph nodes examined specific antibody‐forming cells were observed only occasionally. By subcutaneous injection of Evans blue in the hind footpads it was shown that the subcutis of the hind footpads of these animals is drained by the popliteal lymph nodes, the lumbar lymph nodes, and (to a lesser degree) the sciatic lymph nodes. The presence of trapped immune complexes within lymph node germinal centers was confined to these three nodes. Based on these findings, it is concluded that specific antibody‐forming cells during the secondary response in these mice are induced exclusively in the lymph nodes draining the site of primary immunization