Page 280 - Veterinary Immunology, 10th Edition

VetBooks.ir Follicular DCs

Specialized DCs called follicular DCs (fDCs) are found in the
germinal centers of the spleen, lymph nodes, and Peyer's patches
(Chapter 12). They are also found around localized infection sites

and chronic inflammatory reactions. Follicular DCs are essential for
antibody production and the development of B cell memory. In an
animal that has not previously been exposed to the antigen, antigen

presentation is a passive process. The fDCs simply provide a
surface on which antigen can be presented to B cells. In contrast, in
animals that have previously been exposed to an antigen and
possess antibodies, the antigen and antibody combine to form
antibody-antigen complexes (also called immune-complexes).

Follicular DCs take up these immune-complexes on their surface
and then shed them in membrane vesicles called exosomes. B cells
can take up these exosomes and after processing the antigen,

present it to antigen-sensitive T cells. Follicular DCs can retain
antigens on their surface for more than 3 months. They also
integrate signals from toll-like receptors (TLRs) and other sources to
support effective germinal center responses (Chapter 12).

Dendritic Cell Maturation

Although many DC subpopulations have been characterized, their
most important properties are based on their state of maturity (Fig.
10.5). Thus immature DCs are specialized efficient antigen-trapping

cells. As they mature, DCs undergo cellular reorganization and
become specialized efficient antigen-presenting cells.

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