Ixodid tick salivary gland extracts inhibit production of lipopolysaccharide-induced mRNA of several different human cytokines

Extracts prepared from the salivary glands (SGE) of partially fed adult female Rhipicephalus appendiculatus ticks reduced the expression by human peripheral blood leukocytes (PBLs) of lipopolysaccharide (LPS)-stimulated cytokine mRNA. Treatment with SGE had no obvious effect on cytokine mRNA production when compared with untreated PBLs. LPS treatment induced or increased mRNA production for IFN alpha, IFN gamma, TNF-alpha, IL-1 alpha, IL-1 beta, IL-5, IL-6, IL-7 and IL-8. All the LPS-stimulated cytokine mRNAs were reduced when treated with a mixture of LPS and SGE. The results indicate the potential of ticks in modulating the cytokine network of their vertebrate hosts, possibly to facilitate blood feeding.