OLIGOCLONALITY OF CD8-CELLS IN HEALTH AND DISEASE - AGING, INFECTION,OR IMMUNE REGULATION( T)

Oligoclonality of the CD8+ T cell subset is a common and characteristi c feature of the normal human peripheral T cell repertoire. These clon ally expanded populations are predominantly found in a CD57+ or CD28- CD8+ T cell subset. While CD8 oligoclonality is somewhat more common i n the older age group, it is also very prevalent in young to middle-ag ed adults. Recent experiments have also demonstrated that the clonally expanded populations may actually occur in two distinct subpopulation s of CD8+ CD28- cells, distinguished by the expression of the CD57 sur face marker, A major difficulty with studies involving CD8+ CD28- CD57 + T cells is their relative lack of proliferative capacity. We have re cently investigated the possibility that this phenotype may be due to a state of ''replicative senescence'' in some cases. In this regard, w e have demonstrated that the telomere lengths of CD8+ CD28- T cells ar e generally shorter than that of their CD8+ CD28+ counterparts, consis tent with a distinct replicative history for the CD8+ CD28- population . Additional studies of the normal biology of clonally expanded CD8+ T cells are likely to yield important insights into immune function in health and disease.