Age‐related loss of naïve T cells and dysregulation of T‐cell/B‐cell interactions in human lymph nodes

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Abstract
In this study we analysed the effects of age on T and B lymphocytes in human lymph nodes by comparing lymphocyte subsets in paraffin sections from lymph node tissue taken from healthy young and elderly people. We demonstrate that the relative number of CD8+ T cells decreases with age but that the relative number of CD4+ T cells does not. There is also a very pronounced age-dependent loss of CD45RA+ naïve T cells. The number and size of follicles and the relative number of CD20+ B cells are similar in young and elderly donors. For polymerase chain reaction analysis of the T-cell receptor (TCR) repertoire the TCR-γ gene rearrangements were used as a marker of clonality. This is a reliable tool to detect not only clonal TCR-γδ populations but also TCR-αβ populations. Young donors with clonal T-cell expansions in their lymph node tissue do, however, have a higher number of CD20+ B cells, a higher relative size of germinal centres compared to the follicle mantles and a higher number of immunoglobulin M-expressing cells than young donors without evidence of clonal T-cell expansions. Corresponding changes are not observed in elderly donors with clonal T-cell expansions in their lymph node tissue. In summary our findings demonstrate characteristic effects of aging on human lymph node tissue, the most striking feature being the depletion of naïve T cells and the apparent dysregulation of T-cell/B-cell interactions in old age.