*3.4. C3b Deposition in Hmox1*−*/*<sup>−</sup> *Tissue Samples*

C3b staining in kidney sections obtained from *Hmox1*−*/*<sup>−</sup> rats revealed focal (present in some glomeruli) glomerular deposition (Figure 4, Table 1) compared to WT kidney sections, in which no C3b expression was detected. Specifically, segmental glomerular staining, located in mesangial and endothelial cells of *Hmox1*−*/*<sup>−</sup> kidney tissue sections, was observed. In liver sections from *Hmox1*−*/*<sup>−</sup> rats, there was bridging consisting of inflammatory cells between central veins and biliary ducts with no C3b deposition. In the lung parenchyma of WT rats, C3b immunolocalized in alveolar walls and in cells surrounding bronchioles. On the contrary, in lung parenchyma of *Hmox1*−*/*<sup>−</sup> rats, C3b deposition was barely detectable. Increased C3b deposition, mainly in the red pulp and, to a lesser extent, in the marginal zones, periarteriolar sheath (PALS) and germinal centers, was detected in *Hmox1*−*/*<sup>−</sup> spleen sections (Figure 4, Table 1).

**Figure 4.** C3b staining of WT and *Hmox1*−*/*<sup>−</sup> rat tissue sections. Staining of C3b was detected in kidney, lung and spleen tissues sections. Magnification ×200.
