The present invention relates to cytokine activity regulator molecules (CARMs) and their use in controlling the action of cytokines, particularly chemokines. In particular, the invention relates to CARMs that are derived from parasite salivary glands. The invention also relates to the use of CARMs in the treatment of diseases and allergies and in the production of vaccines that protect mammals, including humans, against the transmission of pathogenic (disease-causing) micro-organisms by certain parasites.