Semiquantitative PCR analysis was used to determine the proportion of wild-type Btk-containing cells in the bone marrow (□) and in purified B cells from the spleen (▩). Groups 1 through 3 were lethally irradiated (900 rad) and received either 5.0 × 106 total cells (groups 1 and 2) or 0.5 × 106total cells (group 3), of which either 5% (groups 1 and 3) or 0.5% (group 2) were wild-type. Groups 4 through 8 received reducing amounts of radiation of 450, 200, 100, 50, or 0 rad, respectively, and all mice received 0.5 × 106 total cells, of which 5% were normal. Five mice were included in each experimental group. Values represent the average for each group ± standard deviation. In groups 2 through 8, all of the mice had between 0.1% and 1% normal Btk in the bone marrow.
