Tick saliva is a complex mixture serving a variety of functions. Soon after attachment, ixodid ticks (except a few species of Ixodes) secrete a milky white material that hardens into a latex-like cone surrounding the hypostome. This is the initial core of the cement cone.

Additional secretions over the next 48-72 hours add cortical layers to the cement; in some species this added cement secretion flows over the skin of the host to further strengthen the attached parasite. The cement secretions are provided by the A, D and E cells of the types II and III granular acini. The chemical composition of the cement consists of a mixture of antigenic and non-antigenic proteins, with substantial lipid and carbohydrate in the innermost layers, the latter compounds mostly in the form of lipo- and glycoproteins. A 90 kDa protein, secreted by the D and E cells of the type III acini, was found to be present in the cement of ixodid ticks of at least several different genera and is believed to the widespread in this family (Jaworski et al. 1990). Following establishment of the cement cone, the salivary glands of the feeding tick expand and protein synthesis accelerates. In studies of feeding A. americanum, total salivary gland protein increased about 15 times that of the protein content of the unfed tick glands. Protein content changed only slightly during the first 3 days of attachment, when little blood uptake occurs. However, intense synthesis commenced after attachment day 3 and protein content increased to 66 µg/tick in the glands on attachment day 12 (virgin females) (Brown and Askenase, 1986).

New proteins were found to have been generated by the glands following the attachment stimulus, while other proteins also present in the unfed glands increased in quantity. In the argasid tick Ornithodoros moubata, a small peptide (about 6,000 Da), presumably secreted in the saliva during feeding, was shown to be an effective anticoagulant, inhibiting clotting time in a dose-dependent manner (Waxman et al. 1990).

Following mating, many protein species disappear (Sauer et al., 1986). Knowledge of these proteins, most of which are unidentified at present, might be of interest since the feeding lesion may be formed in response, at least in part, to these foreign substances.

The feeding period is accompanied by copious secretion of salivary fluids. This pattern of salivary gland activity parallels the sequence of attachment, wound site formation, feeding, mating and repletion that characterizes the parasitic period.

In addition to the cement precursors described previously, histochemical tests have demonstrated a variety of enzymes in the secretory cells of the salivary glands. In B. microplus, certain C cells (c1 cells) contain acetylcholinesterase, a type B carboxyl esterase, uncharacterized proteases, leucine aminopeptidase, monamine oxidase, acid phosphatase and alkaline phosphatase (Kemp et al., 1982); others may also occur in these cells.

Whether some or all of these enzymes are secreted and contribute to the formation of the feeding site or fluid uptake is unknown. Certain salivary enzymes are capable of cleaving complement, specifically the C3 and C5 fractions of the complement cascade, leading to the production of amaphylatoxins.
Tick salivary glands secrete also a veritable cornucopia of pharmacologically active substances, including anticoagulants, prostaglandin E2 (PGE2) and prostacyclin, vasodilators, apyrase, antiinflammatory agents, anti-histamines (in some species) and others. In some species, enzymes are secreted that destroy bradykinins and anaphylatoxins, host proteins that play crucial roles in modulating the inflammatory response. In certain very successful host/parasite associations, e.g., the deer tick Ixodes scapularis (dammini), and the white footed mouse Peromyscus leucopus, unknown salivary agents suppress components of the host immune system, e.g., T.-cells, thereby minimizing rejection.