Expression of CD45 (LCA) on cells of thymus and peripheral organs during gestation. Expression is found early in thymus (beginning at day 52), followed by expression in spleen and PB after the engraftment window closes (day 80). a Representative histograms showing percent expression of CD45 on fetal ovine thymus, PB, spleen, bone marrow, lung, and small intestine at selected time points throughout gestation. b Cumulative data demonstrating expression of CD45 on cells from fetal ovine thymus, spleen, and PB throughout gestation. SEM is shown as error bars.