## 3 Results
In contrast, relatively equal proportions of Ly6C\({}^{\text{Lo}}\) non-classical monocytes expressed Nr4a1 in both the neonatal bone marrow and liver (66.60% vs. 68.42%; \(p=0.67\)) (Figure 2d). Figure 2: Cont. Although Nr4a1 was expressed in moderately high proportions by neutrophils (Figure 2a), macrophages (Figure 2b) and monocyte subsets (Figure 2c,d), we evaluated the mean fluorescent intensity of Nr4a1 to quantify the level of Nr4a1 expression. Ly6C\({}^{\text{Lo}}\) non-classical monocytes had significantly higher expression of Nr4a1 compared to populations in both the liver and the bone marrow (Figure 2e,f). Among the myeloid populations in the neonatal liver, Ly6C\({}^{\text{Lo}}\) non-classical monocytes showed the highest intensity of Nr4a1 expression compared to neutrophils (MFI 6344 vs. 3611; \(p<0.001\)), macrophages (MFI 6344 vs. 2782; \(p<0.001\)), and Ly6C\({}^{\text{Hi}}\) classical monocytes (MFI 6344 vs. 4485; \(p<0.0002\)) (Figure 2e). Ly6C\({}^{\text{Lo}}\) non-classical monocytes also exhibited the highest intensity of Nr4a1 expression in the neonatal bone marrow compared to other myeloid populations (Figure 2f); however, the Nr4a1 expression was significantly higher in liver Ly6C\({}^{\text{Lo}}\) non-classical monocytes than  
Figure 2: **Ly6C\({}^{\text{Lo}}\) non-classical monocytes exhibit the highest expression of Nr4a1. (a) Nr4a1 expression on neutrophils as %GFP positive (\(n=14\); BM 80.03% vs liver 66.52%; \(p=0.02\)). Both organs exhibit similar intensity of expression, represented as Mean Fluorescence Intensity (MFI) (BM 3408 vs liver 3611; \(p=0.25\)). (b) Neonatal BM macrophages show higher expression of Nr4a1 compared to the liver (\(n=14\); BM %GFP 53.46% vs liver 33.83; \(p<0.001\)) (BM MFI 4554 vs liver 2782; \(p<0.0001\)). (c) Higher proportion of Ly6 CHi classical monocytes exhibit Nr4a1 expression in the neonatal BM (\(n=14\); BM 66.13% vs Liver 56.51; \(p=0.03\)); however, MFI is similar between both organs (BM 4575 vs liver 4485; \(p=0.82\)). (d) High proportions of Ly6C\({}^{\text{Lo}}\) non-classical monocytes exhibit Nr4a1 expression in both organs (\(n=14\); BM 66.60 vs liver 68.42%; \(p=0.67\)); however, Ly6C\({}^{\text{Lo}}\) non-classical monocytes the neonatal liver show a higher intensity of expression (BM MFI 5338 vs liver 6344; \(p=0.009\)). (e) Among the myeloid populations in the neonatal liver, Ly6C\({}^{\text{Lo}}\) non-classical monocytes exhibit the highest expression of Nr4a1 compared to neutrophils (MFI 6344 vs 3611, respectively; \(p<0.0001\)), macrophages (MFI 6344 vs 2782, respectively; \(p<0.001\)), and Ly6C\({}^{\text{Hi}}\) classical monocytes (MFI 6344 vs 4485, respectively; \(p<0.0002\)). (f) Ly6C\({}^{\text{Lo}}\) non-classical monocytes also exhibit the highest expression of Nr4a1 in the neonatal BM; however, the degree of intensity is significantly lower than in the liver. \({}^{*}p\leq 0.05;\ ^{**}p\leq 0.01\); \({}^{**}p\leq 0.001\). in bone marrow Ly6C\({}^{\text{Lo}}\) non-classical monocytes (MFI 6344 vs. 5338; \(p\) = 0.009) (Figure 2d). These results demonstrate that although Nr4a1 was present in high proportions in most myeloid populations, the expression was highest in Ly6C\({}^{\text{Lo}}\) non-classical monocytes in the neonatal liver. **Perinatal liver inflammation leads to increased expression of Nr4a1 in hepatic Ly6C\({}^{\text{Lo}}\) non-classical monocytes. ** Having shown that Nr4a1 expression is environment-specific, we next quantified the proportion of mature myeloid populations, and characterized their Nr4a1 expression in the setting of inflammation in the neonatal bone marrow (Figure 3) and liver (Figure 4). We used the well-established murine model of BA, which involves the infection of neonatal pups with Rhesus rotavirus. The injection of RRV during the first 24 h of life results in weight loss, jaundice, and death in the majority of neonatal pups by 21 days [12; 21; 22; 23; 24]. The characteristic histologic findings after RRV infection include periportal inflammation, which is apparent within 3 days.