Page 579 - Veterinary Immunology, 10th Edition

• Explain how KIR receptors can regulate NK cell function and hence immunity to
VetBooks.ir • Explain the functions and properties of NKT cells.
infectious agents.

The structure of lymphocytes reveals few clues as to their functions.

The major cell types involved in adaptive immunity, the T and B
cells, as described in previous chapters, employ millions of highly
diverse, randomly generated antigen receptors. T and B cells,

however, require time to develop in sufficient numbers to affect the
outcome of an infection. They also undergo clonal selection as cells
with self-reactive receptors must be eliminated or suppressed.
Some lymphocytes are, however, able to respond to foreign
antigens or destroy abnormal cells immediately after they are

produced. These are innate lymphoid cells (ILCs) and they are
critical components of the body's defenses. Innate lymphoid cells
fall into two functional groups (Fig. 19.1). One group serves as

helper cells. They regulate the responses to the intestinal microbiota
and play important roles in allergic disease, autoimmunity, and
obesity. The second group consists of cytotoxic cells called “natural
killer” (NK) cells. They serve as a first line of defense against
viruses, some intracellular bacteria, fungi, and parasitic worms.

They eliminate stressed or damaged cells. Some play major roles in
immunity to tumors.

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