This turnover is likely to be driven by routine childhood vaccinations and exposure

to infections, common in this age group. Whole blood cultured in the absence of antigen reduced Ki67 expression to barely detectable levels by day 6, presumably due to cells reverting to a quiescent state. Therefore, this 6-day assay proved to be sufficiently specific and sensitive for the identification of rare, antigen-specific T cells following vaccination in the context of high ex vivo frequencies of Ki67+ T cells. Overall, our data show that outcomes click here of the Ki67 assay correlate strongly with current flow cytometry based whole blood and PBMC proliferation assays. This assay is highly reproducible, versatile, and presents several practical advantages over current techniques. We propose Ki67 as a marker for quantifying antigen-specific T cell proliferation, and utilising this assay to monitor T www.selleckchem.com/products/z-vad-fmk.html cell responses

in large field studies or paediatric studies based on limited blood volumes. The authors declare no financial or commercial conflicts of interest. W.A.H. is supported by the NIH (RO1-AI065653 and NO1-AI70022). T.J.S. is a Wellcome Trust Research Training Fellow (080929/Z/06/Z). “
“The two signal hypothesis of lymphocyte activation proposes that T cells that receive Signal 1 via their T cell receptor (TCR) complex depend on concomitant triggering of costimulatory receptors to achieve full activation (Greenwald et al., 2005 and Watts, 2005). T cell activation is also modulated by inhibitory costimulatory receptors that are able to attenuate TCR-signals. By acting as potent regulators of host-protective as well as pathological processes, T cell costimulatory pathways play a pivotal role in immunity (Saunders et al., 2005, Keir et al., 2008 and Nurieva et al., 2009). Consequently, such pathways are prime therapeutic targets in diseases that

are associated with aberrant T cell responses (Ford and Larsen, 2009 and Li et al., 2009). Likewise, tumor patients or individuals suffering from chronic viral infection might benefit from therapies Exoribonuclease that enhance costimulatory pathways or block inhibitory receptors (Blank and Mackensen, 2007). In this context it is evident that a more complete understanding regarding the function of human T cell costimulatory molecules is a prerequisite for the development of efficient therapeutic strategies. Studies on costimulatory pathways on human cells are hampered by several circumstances. Antigen presenting cells (APC) harbour a plethora of activating and inhibitory ligands with overlapping and redundant functions, which complicate the assessment of the contribution of single molecules to T cell activation processes. Studies on individual costimulatory pathways often rely on the use of immobilized antibodies. Such antibodies might differ from the natural ligands regarding their binding site and affinity.