Page 70 - Veterinary Immunology, 10th Edition

MBL is found in high levels in blood. It has multiple sites that bind
VetBooks.ir oligosaccharides, such as N-acetylglucosamine, mannose, glucose,

galactose, and N-acetylgalactosamine. MBL thus binds strongly to
bacteria such as Salmonella enterica and Listeria monocytogenes. It

binds to Escherichia coli with moderate affinity. It binds strongly to
yeasts such as Candida albicans and Cryptococcus neoformans. It can
also bind viruses such as influenza A as well as parasites such as
Leishmania. Bacteria coated by MBL are readily ingested by

phagocytic cells. MBL plays an important role in activating the
complement system (Chapter 4). There are two forms of MBL in the
pig: MBL-A and MBL-C. These can bind to Actinobacillus suis and
Haemophilus parasuis. Some European pig breeds may express very

low levels of MBL-C and hence, suffer from increased disease
susceptibility.
Multiple CLRs, such as the surfactant proteins SP-A and SP-D,
are produced in the lungs. Six different soluble CLRs (conglutinin,

MBL, pulmonary surfactant proteins [SP-A, SP-D], and collectins-46
[CL-46 and CL-43]) have been identified in mammals. However,
conglutinin, CL-46, and CL-43 have been identified only in Bovidae.
Some CLRs are cell surface PRRs that can bind bacteria, fungi,

and some viruses. The major ones are the dectins and DEC-205. The
dectins bind β-glucans on fungal cell walls and play an important
role in antifungal defense by promoting their intracellular
destruction. Dectin-1 (also called CD369) is expressed by bovine

macrophages, monocytes, and dendritic cells. Bovine dectin-2 is
expressed on Langerhans cells in the skin (Chapter 10). DEC-205 is
expressed on bovine dendritic cells. Another cell-associated lectin is
the macrophage mannose receptor CD206. CD206 recognizes

carbohydrates on diverse pathogens, such as the fungi Candida
albicans and Pneumocystis, the protozoa Leishmania, and viruses such
as bovine viral diarrhea virus.
Selectins are CLRs expressed on vascular endothelial cells that

play a key role in the emigration of leukocytes from the
bloodstream into the tissues in inflammation (Chapter 5).
Other soluble collectins include the ficolins (H-, L-, and M-
ficolins), a family of lectins produced by the liver and some lung
cells. These too can bind bacterial carbohydrates and activate the

complement system (Chapter 4). There are also many cell-

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