Blood Cells - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 173

plasmacytoid dendritic cells. Preclassical dendritic cells circulate in blood and enter
lymphoid tissue, where they give rise to CD8 α+ (a coreceptor for MHC class-1

molecules) and CD8 classical dendritic cells, as well as non-lymphoid tissues,

where they may give rise to CD103

α −

lamina propria dendritic cells (lpDC).
In addition, in normal condition, Ly6C1

+

monocytes (Ly6C1 in Mus muscu-
lus: lymphocyte antigen-6 complex, locus C1) leave the bone marrow to enter
blood. They can then form alveolar macrophages. On the other hand, Ly6C1

−

+

monocytes can become CX3CR1 + lamina propria dendritic cells in non-lymphoid

tissues [ 296 ].
During inflammation, Ly6C1 monocytes engender monocyte-derived dendritic

cells such as TNF- and NOS2-producing dendritic cells (tipDC), 187

+

inflammatory

macrophages, and myeloid-derived suppressor cells [ 296 ].
During infection, Ly6G , 188 Ly6C1 high monocytes differentiate into tip dendritic

cells that produce tumor-necrosis factor-

+

, nitric oxide, and reactive oxygen species
as well as mucosal macrophages that synthesize a different set of inflammatory
mediators.
Relatively long-lived plasmacytoid dendritic cells that lodge in the bone marrow
and all peripheral organs differ from classical dendritic cells. A proportion of these
cells carry characteristic immunoglobulin rearrangements They are specialized in
immune responses to viral infection with a massive production of type-1 interferons.
They also can act as antigen-presenting cells and control T-cell responses [ 296 ].
Plasmacytoid dendritic cells are specialized for viral infections. They use Toll-
like receptors TLR7 and TLR9 in endosomes to sense viral nucleic acids. Receptor
TLR9 then triggers 2 different signaling pathways either from early endosomes or
specialized lysosome-related organelles, hence NF

α

B-dependent production of pro-
inflammatory cytokines or IRF7-dependent synthesis of antiviral type-1 interferons
owing to Adaptor protein-3-dependent TLR9 transfer, respectively [ 314 ]. 189

κ

3.14.2 Thymic Dendritic Cells

After migration into the thymus from blood, thymic dendritic cells inhibit
self-reactive thymocytes and activate T-regulatory cells for central tolerance in
vivo [ 315 ].

187 In the tipDC alias, letter i stands for inducible NOS NOS2).
188 Homo sapiens possesses genes lymphocyte antigen-6 complex, loci G5B to G5C and G6C to
G6F.
189 Both pathways depend on myeloid differentiation primary response gene product MyD88,
an adaptor for TLRs. The AP3 complex interacts with cleaved TLR9 in proteolytically active
VA M P 3 + ,LAMP2 − , PI(3,5)P 2 + ,NF κ B endosomes and facilitates its transfer to the LAMP2 + ,
lysosome-related organelle (LRO), also called IRF7 endosomes, where TLR9 can engage the
TRAF3-IRF7 pathway to cause transcription of IFN genes [ 314 ].