Destruction of BM hematopoietic progenitor and stem cells as bystanders. Sublethally irradiated B6D2F1 mice (5 Gy TBI) were infused with 5 × 106 normal B6 (CD45.2) LN cells to induce BM failure. BM cells from 2 affected mice and 1 control mouse that did not receive LN cell infusion were mixed 1:2 with BM from a B6-CD45.1 congenic codonor, and the cell mixtures were then transplanted into new lethally irradiated, B6D2F1 recipients at 5 recipients per donor. Three recipients each received 10 × 105 B6-CD45.1 congenic codonor BM cells and were used as controls. Recipient survival and donor engraftment were monitored for 10 weeks (A). Sublethally irradiated CByB6F1 mice (5 Gy TBI) were infused with 5 × 106 normal B6 (CD45.2) LN cells to induce BM failure. BM from 1 affected mouse (moderate for BM failure to ensure recipient survival) was mixed 1:2 with BM from a B6-CD45.1 congenic codonor and was injected into 6 lethally irradiated CByB6F1 recipients. Of these, 3 recipients were intraperitoneally injected with 500 μg/d anti-IFN-γ on days 0 and 9, and the other 3 recipients were not. BM cells from 1 control CByB6F1 mouse that did not receive LN cell infusion were mixed 1:2 with BM from a B6-CD45.1 congenic codonor and were injected into 3 lethally irradiated CByB6F1 recipients. Recipients were analyzed 3 weeks after transplantation for CBC and total BM cellularity (B). In both parts of study, each recipient received 5 × 105 donor and 10 × 105 codonor BM cells. Data in panel B are means ± standard error.
