Host cells reconstitute both T- and B-cell lineages in RAG^–/– → F1 bone marrow chimeras. Bone marrow from RAG^—/— mice was used to reconstitute CB6F1 mice as described. (A) The staining profile of one representative mouse is shown. Reconstitution of blood lineages was assessed starting at 3 months after transfer, by antibody staining of lymph node and spleen cells with anti–Thy-1 antibodies (biot-J1j) for T-cell–lineage identification, PE–anti-CD19 for B-cell–lineage identification, together with anti–class I antibodies specific for H-2D^d molecules (FITC-34-4-21S). (B) Myeloid lineages were analyzed by staining peritoneal cavity cells with anti–H-2K^b (right panel) or anti–H-2K^d (left panel) antibodies. Representative staining profiles for one mouse from each group (RAG^—/— → F1 and B6 → F1, broken lines) are shown. Staining of normal F1 mice with each antibody is depicted by solid lines.