Growth and Senescence of the Primary Antibody-Forming Potential of the Spleen

Abstract

Summary: Growth and senescence of the primary antibody-forming potential (PAFP) of the spleen was assessed by culturing spleen cells of 1- to 126-week-old mice together with the test antigen in heavily x-irradiated, genetically compatible, 12-week-old mice. The maximum growth rate of the PAFP of the spleen occurred during the first month after birth. The mean doubling time during this period was ∼4 days in contrast to ∼14 days for spleen and body weights. The highest antibody-forming activity was obtained with cells from 40-week-old mice. The PAFP of the spleen increased ∼600-fold between 1 and 40 weeks of age. In contrast the body weight increased only 8-fold and the spleen weight 4-fold. After 40 weeks of age the PAFP of the spleen decreased gradually with age. Among the very old mice (∼120 weeks) it was only one fourth that of the spleen of 40-week-old mice. With improvement in the animal health program the PAFP of the spleen increased, especially among the very old mice. Evidence was presented to show that the change in the PAFP of the spleen with age is due mainly to the change in the number of potential antibody-forming cells. Furthermore, it was shown that the change in the number of these cells with age is not due to migration of these cells to and from the spleen. The significance of these results is discussed from the standpoint of functional differentiation.