## 4 Discussion
In particular, in the AR\({}_{100}\) group, the effect of suppressing weight loss in the thymus gland, popliteal lymph node, and spleen was comparable to that of the EAP\({}_{200}\) group. The oral administration of AR (100-400 mg/kg) significantly and dose-dependently suppressed the CPA-induced hematopoietic immunosuppression-associated thymus, spleen, and submandibular lymph node weight reduction, showing considerable inhibitory effects at a dose of 100 mg/kg, comparable to that of EAP (200 mg/kg). Pharmacologically active substances should exhibit low cytotoxicity toward normal cells and selective cytotoxicity toward denatured cells [30; 47; 48]. Examination of the MTT cytotoxicity results for spleen cells collected and cultured in the normal vehicle control group at the time of euthanasia showed no significant changes in cell viability in all AR-treated groups (0.01-10 mg/mL) compared to the untreated control group (0 mg/mL). Therefore, at least under the conditions of this experiment, AR does not exhibit cytotoxic or excessive proliferative effects on normal spleen cells. Furthermore, significant reductions were observed in ConA- and LPS-induced splenocytes proliferation in the CPA control group compared to the normal vehicle control group. However, a dose-dependent increase in ConA- and LPS-induced splenocytes proliferation compared to the CPA control group was confirmed in all AR-administered groups. In particular, 100 mg/kg of AR showed an inhibitory effect on the CPA-induced reduction in ConA- and LPS-induced spleen cell proliferation by CPA which was comparable to that of 200 mg/kg of EAP. Generally, ConA promotes the proliferation of T-cells, and LPS induces the division and proliferation of B-cells [11; 15; 30; 49]. Therefore, at least when evaluating the effect of MTT-based splenocytes proliferation in this study, oral administration of AR (100-400 mg/kg) significantly suppressed cell division and proliferation of T- and B-cells by CPA in a dose-dependent manner. It is regarded as indirect evidence of improvement, showing considerable suppressing effects in the AR\({}_{100}\) group, comparable to that of the EAP\({}_{200}\) group. The micronucleleus test using mouse bone marrow smears is the simplest and most reliable method for genotoxicity evaluation [30]. CPA is one of the representative genotoxic substances and causes a marked increase in MNPCE, that is, genotoxicity [18; 19; 30]. A marked increase was confirmed in the number of MNPCE in the CPA control group. However, a dose-dependent decrease in the number of MNPCE was observed in all the AR-administered groups compared to that in the CPA control group. In particular, 100 mg/kg of AR showed anti-mutagenicity by CPA, that is, reduction in genotoxicity, comparable to that of 200 mg/kg of EAP. In contrast, the ratio of PCE (PCE/ (PCE + NCE)) is used as an indicator of the toxicity of test substances to bone marrow cells [50]. The results of this experiment confirmed that the number and ratio of PCE decreased in the CPA control group. However, a dose-dependent increase in the number and ratio of PCE was observed in all AR-administered groups compared to that of the CPA control group. In particular, reduction in bone marrow cytotoxicity by CPA in the AR\({}_{100}\) group was comparable to the reduction effect of EAP\({}_{200}\). At least under the conditions of the micronucleleus experiment in the present study, oral doses of 100, 200, and 400 mg/kg of AR showed a clear and convincing dose-dependent inhibition for bone marrow cytotoxicity and anti-mutagenicity by CPA, showing efficacy comparable to EAP (200 mg/kg). CPA is an immunosuppressive agent that typically inhibits the hematopoietic system, accompanied by a decrease in the number of leukocytes and platelets in the blood, as well as a decrease in HGB and HCT, such as in aplastic anemia [11; 16; 30; 51].