Fig. 3.

Toll-like receptor (TLR) agonists and muramyl dipeptide (MDP) induce cytokines synergistically. (a) Peripheral blood mononuclear cells (PBMCs) from healthy controls and Crohn's disease (CD) patients were stimulated in presence of either 20 ng/ml MDP, 25 µg/ml polyinosine–polycytidylic acid [poly (I : C)], 400 µM loxoribine or 1 µM cytosine-guanoside dinucleotides (CpG) or both MDP and a TLR agonist for 18 h. Supernatants were assessed for granulocyte–macrophage colony-stimulating factor (GM-CSF), tumour necrosis factor (TNF)-α and interleukin (IL)-1β, as described in the Methods. (b) The synergism was calculated by subtraction of baseline secretions induced by MDP and TLR agonists from secretions induced by combined treatment. Healthy: healthy controls carrying none of the three common nucleotide oligomerization domain 2 (NOD2) polymorphisms; CD WT: patients carrying none of the three common NOD2 polymorphisms; CD 1mut: patients carrying two of the three NOD2 polymorphisms; CD 2mut: patients carrying one or more of the three NOD2 polymorphisms. Error bars indicate standard error of the mean. See text for statistically significant associations.