TUMOUR necrosis factor-α (TNF-α) levels in mammalian brain increase during neuroinflammatory diseases. We used the competitive polymerase chain reaction (PCR) to quantify the amount of TNF-α in stimulated and unstimulated brain mast cells (BMC). A cDNA fragment shortened by a deletion of 56 bp was used as an internal TNF-α-specific standard. The immunological stimulus resulted in enhanced TNF-α mRNA expression and increased release of histamine and TNF-α. This is the first time that BMC showing functional FCϵRI-bound IgE receptors have been purified. Our results support the hypothesis that BMC mediators might induce an initial response in neuroinflammatory diseases.