Cultured rhesus embryos (top panel): A. hatched blastocyst on day 0 of co-culture and the following are representative embryos on day 10 of co-culture with B. control, C. PBMCs, D. NK cells, E. monocytes, F. NK cells + monocytes, G. macrophages, and H. NK cells + macrophages. Outgrowth diameter (mm) was measured (lower graph) on day 10 of co-culture blastocysts cultured alone or with either PBMCs, NK cells, monocytes (Mo), NK cells + Mo, macrophages (Mφ) or NK cells + Mφ. Each data point presents a single embryo. Asterisk denotes P < 0.05, compared to Blasts alone.