However, its expression is more widespread and typically elevated in CSF and blood upon acute damage conditions such as ischemic stroke or cerebral hemorrhage, which unselectively affect all brain cell types.26,27 In contrast, GFAP is more specifically expressed in a subset of astrocytes and increases in chronic conditions with astrocytosis, such as amyotrophic lateral sclerosis (ALS).28,29 In contrast to S100B, we found GFAP serum levels to be significantly increased in PBC probands when compared with control individuals (Table 3 and Fig. 4A). Here, GFAP is linked to ischemic stroke.