  In this paper, we study a modification of the mathematical model describing
inflammation and demyelination patterns in the brain caused by Multiple
Sclerosis proposed in [Lombardo et al. (2017), Journal of Mathematical Biology,
75, 373--417]. In particular, we hypothesize a minimal amount of macrophages to
be able to start and sustain the inflammatory response. Thus, the model
function for macrophage activation includes an Allee effect. We investigate the
emergence of Turing patterns by combining linearised and weakly nonlinear
analysis, bifurcation diagrams and numerical simulations, focusing on the
comparison with the previous model.
