Consequences of recombination of Bcl-x alleles on B lymphocytes in the bone marrow and spleen. (A) FACS analysis of bone marrow and spleen cells isolated from MMTVtTA cre bcl-x f/f (Bcl-x^−/−), and littermate controls (Bcl-x^+/+) 4 or 8 weeks after induction. Cells were stained with antibodies against B220 and CD19. (B) 3-primer PCR performed on DNA isolated from bone marrow (BM; lanes 1 and 2) and spleen (SPL; lanes 4 and 5) of MMTVtTA cre bcl-x f/f mice 4 weeks (lanes 1 and 4) or 8 weeks (lanes 2 and 5) after induction. Arrows indicate floxed and recombined alleles. Lanes 3 and 6 are examples of complete recombination, lane 7 is an example of no recombination, and M denotes 100-bp ladder. Vertical bars indicate repositioned lanes. (C) Recombination of Bcl-x f/f alleles in B-cell development. DNA prepared from whole bone marrow (lane 1), fraction A B lymphocytes (lane 2), and fraction B lymphocytes (lane 3) was subjected to 3-primer PCR. Lane 4 demonstrates no recombination; lane 5, nontemplate control; M, 100-bp ladder.