Fig. 5

Complement component activation. (A) Dilated microcirculatory wall in rostral basis pontis is focally positive with immunostaining for C3d (Case 25). (B) Microcirculatory wall shown in (A) is seen here heavily positive for C4d. C5b-9 immunostaining was negative (Case 25). (C) Rostral basis pontis microcirculatory channel with immunostaining positive for C4d, with separation of mural layers (Case 25). (D) C4b positive immunostain associated with PMNs, in perivascular hemorrhage in periaqueductal central gray matter of midbrain, indicates acute perivasculitis with complement component activation (Case 4). (E) C5b-9 positive stain associated with PMNs in perivascular hemorrhage shown in (D) indicates membrane attack complex formation in acute perivasculitis (Case 4). (F) C5b-9 immunostaining in acute perivasculitis in rostral pontine tegmentum (Case 25). Scale bars: 10 μm in (A–F)