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. 2019 Apr 10;6(3):e558. doi: 10.1212/NXI.0000000000000558

Figure 2. Immunohistochemical stains of skeletal muscle biopsies from patients with IMNM, sIBM, or irMyositis.

Figure 2

In IMNM biopsies, PD1+ cells are diffusely distributed in the endomysium (A) and most of them correspond to CD3+ T cells (D). Macrophages in myophagocytosis and endomysial macrophages are PD-L1+ (B) but the sarcolemma of myofibers is not (B). CD68 + macrophages coexpress PD-L2 (E), they colocalize with MHC class I+ sarcolemmal membranes (G), and PD1+ lymphocytes interact with PD-L2+ sarcolemmal structures (F) (A and C, original magnification ×200; B, original magnification ×400; D-F, original magnification ×600). In sIBM biopsies, PD1+ cells are CD3+, and they are detectable in the endomysium surrounding myofibers (H, K). PD-L1 is faintly detectable in macrophages within myophagocytosis but not on the sarcolemma and not on endomysial or perimysial macrophages (I). The sarcolemma of myofibers and macrophages are PD-L2+ and colocalize with sarcolemmal MHC class I (J, N). CD68 + macrophages coexpress PD-L2 (L), and PD1+ lymphocytes only occasionally interact with PD-L2+ sarcolemmal structures (M) (H-J, original magnification ×200; K-N, original magnification ×600). In irMyositis, PD1+ cells are detectable in the endomysium and they are CD3+ with variable intensity (O, R). PD-L1 is positive on macrophages but not all CD68 + macrophages express PD-L1 (P). The sarcolemma of myofibers is moderately PD-L2 positive (Q) and faintly coexpresses MHC class I (U). CD68 + macrophages interact with PD-L2+ sarcolemmal structures (S). Single PD1+ T cells interact with PD-L2 sarcolemmal structures (T) (O-Q, original magnification ×200; R-U original magnification ×600). IMNM = immune-mediated necrotizing myopathy; irMyositis = myositis induced by immune checkpoint inhibitors; sIBM = sporadic inclusion body myositis.