α-B-Crystallin as a Tissue Marker of Epileptic Foci in Paediatric Resections

Background: We studied α-B-crystallin, a small heat shock chaperone protein upregulated by various “stresses”, as an immunocytochemical tissue marker of epileptic foci. Methods: We examined 45 resected brain tissues of epileptic patients, 16 months to 23 years. Postmortem brains of 2 epileptic children and 20 normal fetuses and neonates of 10-41 weeks gestation similarly were studied. Immunocytochemical demonstration of α-B-crystallin was supplemented by neuronal, glial and inflammatory cell markers and electron microscopy (EM) in surgical cases. Autopsy brain tissue of children without epilepsy or neurological disease served as controls. Results: In all resections, α-B-crystallin was overexpressed in astrocytes and oligodendrocytes, including satellite cells adherent to neurons, and occasionally in neurons of neocortex, hippocampus and amygdala. In six cases, reactivity was most intense at or near the epileptic focus, with a diminishing gradient of intensity for 2-3 cm; similar focal expression was seen in autopsy cases. Presence or absence of histological structural lesions was independent of α-B-crystallin expression. Balloon cells and giant atypical cells in tuberous sclerosis were intensely reactive. Reactivity was present in DNETs. No correlation occurred with microglial activation, inflammation or gliosis; no ultrastructural alterations were seen. No expression was seen in fetal brains at any age. Conclusions: Immunoreactive α-B-crystallin is a reliable tissue marker of epileptic foci, regardless of presence or absence of structural lesions; at times it maps the extent of a focus.