Tissue-specific lectin/haemagglutinin activities have been investigated for both soft and hard ticks, although there are comparatively few papers published. Some tick lectins are proteins with binding affinity for sialic acid, various derivatives of hexosamines and different glycoconjugates. Most tick lectin/haemagglutinin activities are blood-meal enhanced, and could serve as molecular factors of self/non-self recognition in defence reactions against bacteria or fungi, as well as in pathogen/parasite transmission. Dorin M, the plasma lectin of Ornithodoros moubata, is the first tick lectin to be purified from tick haemolymph, and the first that has been fully characterized. Partial characterization of other tick lectins/haemagglutinins has been performed mainly with respect to their carbohydrate-binding specificities and immunochemical features. The main goal of this review is to provide an overview of our knowledge of lectins as tissue specific carbohydrate-binding proteins of ticks with emphasis on their structural properties and functional roles either in defence reactions or pathogen transmission. Other lectin reviews have been published dealing with tissue-specific lectins in blood-sucking arthropods (e.g. Ingram & Molyneux, 1991; Grubhoffer, Hypša & Volf, 1997; Grubhoffer & Jindrák, 1998). In addition, several publications have drawn attention to plant and animal lectins, and to lectins as tools in modern glycobiological research (e.g. Jacobson & Doyle, 1996; Rhodes & Milton, 1998).
Research on lectins began in 1888 with publication of the doctoral thesis of Herman Stilmark at the University of Dorpat, Estonia, on the agglutinins of the seeds of castor bean Ricinus communis (Sharon & Lis, 1988).