Individual or pooled single-cell suspensions from thymus or spleen were obtained as previously described.26,30,31 (link) Axillary and inguinal lymph nodes were collected and mechanically dissected before counting the cells and staining them with flow cytometry antibodies. Cell counts were performed by Z2 particle counter (Beckman Coulter, Pasadena, CA), Spark 10M (Tecan, Zürich, Switzerland), or hemocytometer. CD45 cells were enriched by magnetic bead separation using LS columns and CD45 beads (Miltenyi Biotech,). Peripheral blood was collected into EDTA capillary pipettes (Drummond Scientific, Broomall, PA). Peripheral blood counts were performed on Element Ht5 automatic counter (Heska, Loveland, CO).