Page 279 - Veterinary Immunology, 10th Edition

shaped cytoplasmic granules called Birbeck granules, whose
VetBooks.ir function is unclear. Their long dendrites form an extensive network

that is ideally situated to capture foreign antigens (Fig. 10.4). These
antigens include not only invading microbes but also topically

applied antigens, such as the resins of poison ivy, or intradermally
injected antigens, such as those in mosquito saliva. Langerhans cells
influence the development of skin immune responses, such as
delayed hypersensitivity and allergic contact dermatitis (Chapter

33). They express multiple pattern-recognition receptors (PRRs),
including the C-type lectins langerin and DC-SIGN (see below) that
can bind bacteria, fungi, and some viruses. Once antigens are
captured, the Langerhans cells migrate to draining lymph nodes,

where they present the antigen to T cells. Some immunologists
regard Langerhans cells simply as specialized macrophages.

FIG. 10.4 This dark red cell in the epidermis of a dog is a
Langerhans cell stained for the protein vimentin. Note that its
dendrites extend between the epidermal cells so that it can
effectively trap antigens. (Courtesy Dr. K.M. Credille.)

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