Although it is generally recognized that the function of the immune system declines with age, the nature of the underlying defects is still poorly understood. We now demonstrate the predominance of CD8⁺CD28⁻ T cell clonal expansions in elderly persons who fail to produce specific Abs following influenza vaccination. These clones express effector cell markers and are mostly CD45RA⁺. When isolated and put into culture, they are unable to proliferate, but produce IFN-γ (but no IL-5) upon stimulation with anti-CD3 or autoantigen. These autoreactive CD8⁺ type 1 effector cells seem to trigger a Th1 polarization, as CD4⁺ T cells from elderly persons without in vivo Ab production produce Th1, but only low amounts of Th2 cytokines upon in vitro stimulation with PHA. Therefore, the increased occurrence of CD8⁺CD28⁻ clonal expansions may be decisive for the development of immune deficiency in the elderly.

In a worldwide collaborative effort, 19,630 Y-chromosomes were sampled from 129 different populations in 51 countries. These chromosomes were typed for 23 short-tandem repeat (STR) loci (DYS19, DYS389I, DYS389II, DYS390, DYS391, DYS392, DYS393, DYS385ab, DYS437, DYS438, DYS439, DYS448, DYS456, DYS458, DYS635, GATAH4, DYS481, DYS533, DYS549, DYS570, DYS576, and DYS643) and using the PowerPlex Y23 System (PPY23, Promega Corporation, Madison, WI). Locus-specific allelic spectra of these markers were determined and a consistently high level of allelic diversity was observed. A considerable number of null, duplicate and off-ladder alleles were revealed. Standard single-locus and haplotype-based parameters were calculated and compared between subsets of Y-STR markers established for forensic casework. The PPY23 marker set provides substantially stronger discriminatory power than other available kits but at the same time reveals the same general patterns of population structure as other marker sets. A strong correlation was observed between the number of Y-STRs included in a marker set and some of the forensic parameters under study. Interestingly a weak but consistent trend toward smaller genetic distances resulting from larger numbers of markers became apparent.