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