Distribution and lytic activity of NK cell subsets in the elderly

Old subjects present an increased number of NK cells associated with a decreased lytic activity of isolated and cloned CD16 cells. Recently, two new surface molecules of 58 kDa, identified by the monoclonal antibodies GL183 and EB6, have been described. The presence of these molecules, which can be coexpressed on CD16+ cells allows the recognition of the NK cell subsets whose cytolytic activity is restricted to different allospecificities. This study investigated a group of old subjects to determine whether a particular distribution or a different lytic activity of NK subsets, defined by MoAbs GL183 and EB6, is involved in the altered cytolytic activity found during ageing. Further, we investigated whether the ageing process might be responsible for a restriction of the NK cell repertoire involved in the recognition of allogenic cells. We found that old and young subjects have a similar proportion of double positive and double negative GL183/EB6 cells, while in the old group single positive subsets were increased. The lytic activity of sorted NK subsets isolated from old and young subjects was similar, although double positive and double negative cells from the old presented a lower cytotoxic activity. The addition of IFN-beta or rIL-2 to the culture medium restored the lytic activity to the level found in young subjects. These data show that the decreased NK lytic activity found in the old subjects is shared out among the different NK subsets and normal aged subjects do not lose the NK repertoire found in the young.