The relationship between antibody formation and deoxyribonucleic acid (DNA) synthesis in mouse spleen during primary and secondary response to sheep erythrocytes (SRC).

Incorporation of [H]thymidine into the spleens of intact mice during the primary and secondary responses to SRC has been studied. In both responses, auto-radiographs show a well marked increased incorporation of [H]thymidine by cells in the peri-arteriolar zone during days 1 and 2. The degree of labelling indicated that many of these cells were in S phase in preparation for mitosis. A similar response occurred in cells situated in the mantle layer on day 3 to day 4 of the primary response, but was much less evident in the secondary response. This was in keeping with the results of scintillation counting which showed that increased uptake of [H]thymidine was more sustained in the primary than in the secondary response to SRC. Many lightly labelled cells indicating metabolic turnover of DNA developed in the red pulp of the spleen at times which coincided with the maximum development of antibody-producing cells (PFC) which occurred about 24 hours earlier in the secondary than in the primary response. Germinal centres showed many lightly labelled nuclei. In both primary and secondary responses these areas enlarged, becoming maximal in size after the peaks of PFC were achieved. It was concluded that the enlargement of germinal centres was the result of trapping of cells in the areas rather than proliferation. From these studies it appears that metabolic turnover of DNA occurred in areas of the spleen intimately associated with antibody formation. The possible role of this process in antibody synthesis is discussed in the light of these observations.