Phenotypic recovery of peripheral T and B cells.

Lethally irradiated (8.5 Gy) BALB/c mice were transplanted with one unit (2.5 × 10⁶) of T-cell–depleted bone marrow cells from C57BL/6 (closed triangles) or SJL/J (closed squares) mice or the combination of both (closed circles). Peripheral blood was harvested in EDTA microtubes. Then, 50 μL blood was incubated with antibodies at room temperature for 15 minutes. The stained samples were then processed in Multi-Q-Prep to lyse the red cells. The samples were analyzed in a Coulter EPICS-XL flow cytometer equipped with System II software. The absolute counts were determined by using Flow-Count. The controls were mice that received a single-donor graft (open triangles indicate C57BL/6; open squares, SJL/J) at a dose equivalent to that of the combined group (5 × 10⁶). The values represent the mean + SE of 3 to 15 animals per group. Similar experiments have been repeated twice. The pretransplantation levels (per microliter blood) are as follows: CD4⁺ T cells, 1912 ± 634; CD8⁺ T cells, 322 ± 246; B220⁺ cells, 1757 ± 422. P values as compared with the C57BL/6 + SJL/J group are shown in Table 2.