To better understand the contribution of complement activation and anaphylatoxin receptor expressing cells to processes of compartmentalised inflammation and cortical pathology, our post-mortem study of MS investigated: (i) the presence of products of complement activation at the brain surfaces (pia and around blood vessels of the cortex); (ii) the association between complement, microglial and astroglial activation and; (iii) differences in complement C3aR1 and C5aR1 positive cell numbers in areas of cortical demyelination in comparison to non-lesion and control GM samples. This evidence concerns the gene C3AR1 and myeloid sarcoma.