Innate Immune Response (Ch14)
Overview of Innate Defense System
First lines of Defense
• Physical Barriers
– Skin
– Mucous membranes
• Antimicrobial substances
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Lysozyme
Peroxidase enzyme
Lactoferrin
Defensins
• Normal Flora
Epithelial Barriers
Skin as the first line of defense
• Intact skin protects
– Epidermis
– Dermis
Mucous membranes line the interior of
the body
Ciliated cells are important…where?
Antimicrobial Substances
Microbial Barriers
• Normal flora (biota) play a role in keeping
the body protected
– Competitive exclusion
– E. coli produce bacteriocins which kill
Salmonella and Shigella
Cells of the Immune System
• Cells move from one system to the next
• Found in blood, developed from bone
marrow
• What are some of these cells??
– Granulocytes (neutrophils, basophils,
eosinophils)
– Mononuclear phagocytes
– Dendritic cells
– Lymphocytes
Dendritic cells
• Branched cells, important in adaptive
immunity
• Develop from monocytes, engulf material
and bring it to other cells for analysis
How do cells of the immune
system communicate?
• Cytokines
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Chemokines
Colony-stimulating factors
Interferons
Interleukins
Tumor Necrosis factors
Cytokines and their function
Interferons
• Three types of glycoproteins
– Alpha
– Beta
• Produced by virus infected host cells, induce mRNA
for antiviral proteins
– Gamma
• Produced by lymphocytes
Interferons inhibit viral replication
Sensor systems in the blood,
tissues and cells
• Can detect signs of tissue damage or
microbial invasion
• Respond by
– Detecting parts of bacteria/viruses using pattern
recognition receptors (PRRs)
– Directly destroy bacteria using complement
– Recruit other components of host defense
Pattern Recognition Receptors
• Toll-Like receptors (TLRs)
– Membrane bound receptors which detect
bacterial parts
• NOD-like receptors (NLRs)
– Cytoplasmic proteins detect bacterial parts
• RIG-like receptors (RLRs)
– Cytoplasmic proteins detect viral RNA
Toll-like receptors (TLRs)
• A type of PRR
• Recognize peptidoglycan,
lipopolysaccharide,
flagellin, certain nucleotide
sequences unique to
bacteria
Toll-like receptors
NOD-like receptors (NLRs)
RIG-like receptors
• Cytoplasmic proteins which detect viral
RNA in a cell
• Activate secretion of interferon and
inflammatory response chemicals
• Overall goal is to inhibit viral replication
Complement Proteins are part of
the Complement system
• Consists of a collection of 9 interacting
proteins found in blood and tissues
• Activation of these proteins promote
– Opsonization
– Inflammatory response
– Lysis of foreign cell
How are the complement proteins
activated?
Regulation of the complement system
What have we covered so far?
• The innate immune system is composed of
– Cells
– Chemicals released by cells to communicate
with each other
– Receptors to recognize invaders
• We need to look at the processes of
phagocytosis and inflammation
How do phagocytes work?
Fever is a nonspecific response
• Il-1 increases T
lymphocytes
• Decreases available
iron
• Increases cellular
reactions
Inflammation response
• What are the key cells involved?
• What are the four key symptoms of
inflammation?
• What activates the inflammation response?