〔Abstract〕 To investigate the effects of different doses of X ⁃rays irradiation combined with allogeneic lymphocyte infusion on the establishment of aplastic anemia in mice. Methods Forty BALB/c mice were randomly divided into four groups : the 3 Gy group (n = 9) , the 4 Gy group (n = 9) , the 5 Gy group (n = 10) , and the con⁃trol group (n = 12) . In the 3 Gy , 4 Gy , and 5 Gy groups , the experimental mice were exposed to corresponding do⁃ses of X ⁃ray and then intravenously infused with 0. 2 mL mixed suspension of the thymus and spleen cells from DBA/2 mice , at a concentration of 1 × 107 cells/mL , within 4 hours after irradiation. The control group did not un⁃dergo X ⁃ray irradiation and infused with an equivalent volume of physiological saline instead. Blood samples were collected from the orbital venous plexus of BALB/c mice and analyzed using an animal automated hematology analy⁃zer to measure peripheral blood parameters , including red blood cells ( RBC) , white blood cells ( WBC) , and platelets (PLT) . The general condition of mice was monitored daily , and survival rates were recorded for each group. At the experimental endpoint , the tibias were harvested for hematoxylin and eosin (HE) staining , while the femurs were used to prepare bone marrow smears for morphological examination. For the 5 Gy group , T ⁃cell subsets(ELISA) at the endpoint. Results In the 3 Gy group , pancytopenia was observed , but platelet recovery occured rapidly , returning to normal levels by day 17 post⁃modeling. No deaths occurred during the observation period. At myeloid⁃to⁃erythroid (M/E) ratio , and no significant morphological abnormalities were noted in cells at any devel⁃with hematopoietic cells. In the 4 Gy group , pancytopenia persisted throughout the observation period. The survival rate was 90% . Endpoint analysis showed hypocellular marrow by morphological examination. HE staining indicated minimal fatty infiltration in the bone marrow tissue. In the 5 Gy group , pancytopenia was observed , though erythro⁃cyte counts returned to normal levels by day 24. The survival rate during the observation period was 50% . End⁃oint analysis revealed vacuolization of marrow particles and reduced hematopoietic cells with predominantly non⁃hematopoietic cells in bone marrow morphology. HE staining demonstrated severe fatty infiltration in the bone mar⁃row tissue , with scarcity of immature cells and hematopoietic precursor cells. Flow cytometry analysis showed a de⁃creased proportion of CD4 + T cells (% ) and an increased proportion of CD8 + T cells (% ) . ELISA confirmed ele⁃vated secretion of negative hematopoietic regulators : interferon⁃gamma ( IFN⁃γ) and tumor necrosis factor⁃alpha (TNF⁃α ) . Conclusion Combined administration of varying radiation doses with allogeneic lymphocyte infusion consistently induced peripheral blood cytopenia in mice , characterized by reductions in RBC , WBC , and PLT counts. Integrated analysis of bone marrow morphology , histopathological assessment via HE staining , and immuno logical parameters confirmed that a mouse model of aplastic anemia can be successfully established using 5 Gy X ⁃ ray irradiation coupled with infusion of 2 × 106 allogeneic lymphocytes.