Increase of CD5(+) B cells during adolescence in female mice

We examined physiological changes in CD5(+) B lymphocytes in mice associated with aging (from 1 or 5 to 50 weeks of age). The most predominant populations of lymphocytes among these mice were mainly CD5(-) B cells in the spleen and peritoneal cavity, and T cells in the thymus. However, in the spleen, CD5(+) B cells increased from 1 to 15 weeks, and then decreased with aging. In the thymus, CD5(+) B cells increased from 3 to 9 weeks of age, and subsequently became more predominant than CD5(-) B cells. In the peritoneal cavity, CD5(+) B cells increased from 5 to 9 weeks of age, became the most predominant population in lymphocytes at 7 to 9 weeks of age, and decreased with aging. The proportion of CD5(+) B cells in total B cells increased from 5 to 7 or 9 weeks of age, and then decreased with aging, with the highest proportion at 9 weeks of age in the spleen (15%), thymus (94%), and peritoneal cavity (54%). These findings indicate that CD5(+) B cells increase physiologically during mouse adolescence, and subsequently decrease with aging.