Microarray analysis reveals similarity between CD8+CD28- T cells from young and elderly persons, but not of CD8+CD28+ T cells

We isolated highly purified CD8(+)CD28(+) and CD8(+)CD28(-) T cell populations from healthy young and elderly persons for gene expression profiling using Affymetrix oligonucleotide microarrays. We demonstrate that the gene expression profile of CD8(+)CD28(-) T cells is very similar in young and elderly persons. In contrast, CD8(+)CD28(+) in elderly differ from CD8(+)CD28(+) in young persons. Hierarchical clustering revealed that CD8(+)CD28(+) in elderly are located between CD8(+)CD28(+) in young and CD8(+)CD28(-) (young and old) T cells regarding their differentiation state. Our study demonstrates a dichotomy of gene expression levels between CD8(+)CD28(+) T cells in young and elderly persons but a similarity between CD8(+)CD28(-) T cells in young and elderly persons. As CD8(+)CD28(+) T cells from elderly and young persons are distinct due to a different composition of the population, these results suggest that the gene expression profile does not depend on chronological age but depends on the differentiation state of the individual cell types.