Callithrix jacchus (CJ) is a primate which is susceptible to a form of experimental encephalomyelitis that resembles multiple sclerosis (MS). Human studies seeking disease related genes for MS have identified candidates including interleukin 1ß (IL1ß) and its receptor antagonist IL1ra. We therefore attempted to measure expression of IL1ß and IL1ra in the brain of CJ and examined whether mRNA levels are affected by peripheral application of lipopolysaccharide (LPS). For cloning of partial sequences, RNA was extracted from frontal cortex. RT-PCR was performed with human primers, products were cloned for sequencing. CJ – specific primers/probes were developed for mRNA determinations by TaqMan PCR. Seven adult male CJ were subcutaneously injected with 40µg LPS, while 7 animals received NaCl injections. 3 hours later, animals were sacrificed by an overdose of ketamine. Brain sections were cut on a cryostat and specific areas (frontal Cortex, Hippocampus, Claustrum) were dissected using the micropunch technique. These areas were chosen because human studies have shown, that MS is associated with degenerative changes in these parts of the CNS. LPS reduced serum testosterone levels (1.3±0.4 vs. 0.5±0.09 ng/dl), while prolactin and IL1ß levels increased (9.2±1 vs. 20.4±4.9 ng/ml and 0.098±0.03 vs. 1.75±0.4 pg/ml, respectively, all results p<0.05). These endocrine changes were associated with significant increases of IL1ß- mRNA levels in the frontal cortex (15.3 fold), hippocampus (13.2 fold) and claustrum (12.8 fold). In contrast, mRNA levels of IL1ra remained unchanged in all three areas.