IL-1B is secreted by microglia and
absorbed by astrocytes and
neurons. It is free to diffuse
throughout the environment.
Microglia secrete IL-1B into the
same grid space at which they are located when their internal
concentration of soluble amyloid exceeds the triggering
concentration parameter. The appropriate checks are made
so that the microglia concentration is taken into
account. The rate of secretion is the
product of the IL-1B secretion rate, u, and
the microglia concentration, q, so that
IL-1B diffuses according to the diffusion properties
discussed above. Initially, the diffusion coefficient
equals the diffusivity parameter throughout
space. However,
astrocyte blocking may reduce the
diffusion coefficient in specific regions.