3.3.4. Macrophages

Similar to monocytes, we hypothesise that macrophages experience diffusion but not convection. Once monocytes are in the arterial wall, they differentiate into macrophages. Furthermore, macrophage phagocytes oxidised LDL, and once they cannot ingest a greater amount of oxidised LDL, they suffer apoptosis and become foam cells. These two phenomena are represented in the macrophage reactive terms:

$$\frac{\partial \mathbb{C}\_{M,w}}{\partial t} + \nabla \cdot (-D\_{\mathbb{C}\_{M,w}} \nabla \mathbb{C}\_{M,w}) = d\_{\mathbb{m}} \mathbb{C}\_{m,w} - \frac{LDL\_{\text{ox},r}}{n\_{\text{FC}}} \cdot \mathbb{C}\_{\text{ox}LDL\_w} \mathbb{C}\_{M,w} \tag{39}$$

In Equation (39), *LDLox*,*<sup>r</sup>* is the constant rate of oxidised LDL uptaken by macrophages, and *nFC* is the maximum amount of oxidised LDL that a single macrophage must ingest to transform into a foam cell.
