Age dependent decline in CD47 expression on circulating mouse erythrocytes and susceptibility to destruction by macrophages (85.11)

Abstract

Abstract We have recently described a novel technique to tag a cohort of mouse erythrocytes released into blood circulation over a defined time window, and follow age related changes in this population in circulation (Khandelwal S and Saxena RK, Expt. Gerontol. 41, 855, 2006). In the current study, we report the kinetics of age dependent decline in CD47 expression on circulating erythrocytes and its role on destruction of senescent erythrocytes by macrophages. CD47 expression was highest on erythrocytes freshly released into circulation and fell steadily thereafter. Oldest erythrocytes in circulation had 30% lower expression of CD47 than the youngest erythrocytes. Depletion of macrophages by administration of clodronate loaded liposomes resulted in a significant fall in the average expression of CD47 on erythrocytes of young (<15 d), intermediate (15–40 d)and old (>40 d) age groups, but a significant increase was observed only in the numbers of old erythrocytes in blood. A time dependent accumulation of CD47low erythrocytes was noted in blood and spleen though the accumulation was markedly higher in spleen. Taken together our results support the proposition that an age dependent fall in CD47 expression on blood erythrocytes may have a role in regulating the destruction of senescent blood erythrocytes by the macrophages. This work was supported by a research grant from the Department of Science and Technology, Government of India.