Memory B Cell Subpopulations in the Aged

The literature on immunosenescence has focused mainly on T cell impairment. With the aim of gaining insight into B cell immunosenescence, the authors investigated the serum IgD levels in 24 young and 21 old people and analyzed their relationship with the number of CD19 CD27 memory cells. Serum IgD were quantified by the use of radial immunodiffusion and the lymphocyte population CD19 CD27 was identified by a FACScan flow cytometer. Serum IgD levels were significantly lower (p 0.0001) in old subjects, and the percentage of CD19 CD27 lymphocytes were significantly increased (p 0.01) in old subjects. Finally, a significant negative correlation was found (p 0.01) between serum concentrations of IgD and CD19 CD27 . The present results show that the levels of IgD are negatively agerelated to the amount of B memory cells. This suggests that the B repertoire available to respond to new antigenic challenges is decreased in the elderly also. In fact, many memory IgD B cells fill immunologic space, and the number of naïve IgD B cells is dramatically decreased. Therefore, these preliminary results suggest that a decrease of naïve IgD CD27 B cells and a concomitant increase of memory IgD CD27 B cells could represent hallmarks of B immunosenescence, might provide biomarkers related to the lifespan of humans, and could be useful for the evaluation of antiaging treatments.