(A) Quantification of meningeal CD20⁺ B cell count and CD3⁺ T cell count in 27 MS donors and 9 nonneurological controls (NNCs) showing enrichment in MS donors versus NNCs. The median for meningeal CD20⁺ B cell count (orange dotted line) and meningeal CD3⁺ T cell count (blue dotted line) was used to stratify MS donors in high versus low meningeal B or T cell count. (B) Quantification of meningeal CD3⁺ T cell count showing significant enrichment of T cells in meninges adjacent to GML versus NAGM in MS donors with high (n = 14) but not low (n = 13) meningeal T cell count. (C) Quantification of meningeal CD20⁺ B cell count showing significant enrichment of B cells in meninges adjacent to GML versus NAGM in MS donors with high (n = 14) but not low (n = 13) meningeal T cell count. (D–G) Representative immunohistochemical staining for CD3 (D and E, arrows) and CD20 (F and G, arrows) in meninges adjacent to subpial GML or NAGM in MS donors with high CD3⁺ or CD20⁺ meningeal cell count. (H) Quantification of the proportion of subpial gray matter that did not stain positive for myelin in MS donors with high versus low CD3⁺ T cell meningeal count. (I) Spearman’s correlation coefficient between meningeal CD3⁺ T cell count and the proportion of subpial gray matter that did not stain positive for myelin. (J) Quantification of the proportion of subpial gray matter that did not stain positive for myelin in MS donors with high versus low CD20⁺ B cell meningeal count. (K) Spearman’s correlation coefficient between meningeal CD20⁺ B cell count and the proportion of subpial gray matter that did not stain positive for myelin. In A–C each data point represents mean cell count (mean ± SD) in all fields analyzed per case. Statistically significant differences determined by nonparametric Mann-Whitney test (A, H, and J) or nonparametric Kruskal-Wallis test followed by Dunn’s correction for multiple comparisons (B and C). Scale bars: 100 μm (D–G).