Page 948 - Veterinary Immunology, 10th Edition

VetBooks.ir Immunity to Arthropods

When arthropods such as ticks, fleas, or mosquitos bite an animal,
they inject saliva. This saliva contains digestive enzymes that assist

the parasite in obtaining its blood meal. The saliva also contains
components designed to minimize host responses (Fig. 28.12).

FIG. 28.12 Immunosuppressive and antiinflammatory factors
found in tick saliva. Collectively they act to permit prolonged tick
attachment and feeding.

Host immune responses to injected arthropod saliva are of three
types. Some salivary components are of low molecular weight and
cannot function as normal antigens. They may, however, bind to

skin proteins such as collagen and then act as haptens, stimulating
Th1 responses. On subsequent exposure, these responses may
induce a delayed hypersensitivity reaction. Other salivary antigens
may bind to epidermal Langerhans cells and induce cutaneous
basophil hypersensitivity, a Th1 response associated with the

production of IgG antibodies and a basophil infiltration. If these

948