Characterization of the lymphocyte subsets in multiple sclerosis lesions in comparison to inflammatory and non-inflammatory controls. (A–D) The inflammatory response in the lesions is dominated by CD3+/CD8+ T lymphocytes, while the contribution of CD4+ T cells is minor; the number of CD20+ B cells is highly variable between lesions and cases; while T cells are similar in number and distribution between multiple sclerosis and inflammatory controls, B cells are more selectively enriched in multiple sclerosis lesions in comparison to other inflammatory controls; T and B cell infiltrates are very sparse in non-inflammatory controls. (E–L) A more detailed analysis shows that T and B cells are significantly more numerous in the lesions of acute and relapsing multiple sclerosis in comparison to those in progressive multiple sclerosis (E–H). The stars shown in the acute multiple sclerosis and relapsing-remitting multiple sclerosis (RRMS) data indicate those patients, who have not been treated with corticosteroids. In addition, active lesions show the highest degree of inflammation, followed by slowly expanding lesions (SEL) and inactive lesions (I–L). Significance levels: *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001.