PVL contain high levels of activated microglia expressing major histocompatibility complex class II (MHCII) and the costimulatory molecules B7-2 and CD40, along with minichromosome maintenance protein 2 (MCM-2) suggesting a more immune-activated and proliferative-permissive environment within PVL [12]. The gene discussed is CD40; the disease is periventricular leukomalacia.