Not a few attempts to prevent severe acute GVHD in animal models by inhibiting macrophage CP-863187 function as an antigenpresenting cell or modulating macrophage phenotype have been reported and some were successful. However, severe adverse effects such as infections occurred occasionally since inflammatory macrophages play important roles in both innate and acquired immune response. Minimal risk of infection can give DP treatment an advantage over those pretreatment. Genetic modification of cells in human and experimental models is essential when deciphering gene-encoded information during developmental, physiological, and pathological states. A complete understanding of the mechanisms governing gene function is essential in areas such as development of regenerative and reparative medicine, gene therapy, genetic models of disease and reliable systems in drug discovery. One of the uses of homologous recombination is to generate stable ����knock-in���� cell lines with selectable markers expressing specific cDNAs or RNAi that make it possible to purify specific cellderived cell types from a mixed population and to decipher their roles in cell stemness, differentiation, and fate, as well as in homeostasis and disease. However, efficient and safe genetic targeting at stable and harmless loci PRL-3 Inhibitor I remains elusive and is a limitation for low-to-medium throughput strategies. Genetic modification based on homologous recombination, heterologous site-specific recombinase, and recombinase-mediated cassette exchange has been widely used in chromosomal targeting, although currently available technology is laborious. Zinc-finger nuclease�Cbased and meganuclease-based technologies have recently been designed for site-specific editing and are proving to be exceptionally promising tools, although they are time-consuming and expensive. In addition, these approaches are either inefficient or restricted in their applicability, thus preventing them from being used in large-scale functional genetic screening studies. At present, the most efficient strategies for gene targeting combine tagged cellular systems containing recombination target sites from phages or yeasts with selected harmless genetic loci that are prone to recombination, for example, ROSA26, hprt, AAVS1.