Efficacy of engraftment of human PBMC in NSG mice. (A) Schema of 9-wk engraftment protocol. Mice were irradiated 24 h prior to i.v. injection of 1 × 106 human PBMC and spleens were isolated on day 63. (B) Schema of 4-wk engraftment protocol starting with i.v. injection of 10 × 106 human PBMC on day 1. Isolation of spleens was performed on day 28. (C) Representative staining of CD3 vs. CD45 in blood withdrawals of individual mice engrafted with the 9-wk or the 4-wk protocol on week 2, 3 and 4. Italic numbers given beside the CD3/CD45-positive population indicate the percentage of CD62L-positive cells within the double-positive fraction.