BIOL 462 Lecture 3: BIOL 462 Lecture 3 notes
18 Feb 2019
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Victoria Richard BIOL 462 – Lecture 3: innate immunity
Review of lecture 2
- Hematopoiesis is highly regulated
o HSC > myeloid progenitor > monocytes, granulocytes, megakaryocyte, erythroid
progenitor, dendritic cells
▪ First responders to infections
o HSC > lymphoid progenitor > NK, T and B cells, dendritic cells
▪ Adaptive immunity
- Primary lymphoid organs and microenvironments
o Bone marrow (site varies among species)
o Thymus (evolutionary conserved)
- Secondary lymphoid organs (spleen, lymph nodes, MALTs, Peyer’s patches)
o Patrolling phagocytes
- Lymphh and lymphatic system sweep antigens from the whole body and present them
to the immune. Cells
- Barriers are the organism’s first line of defense
- Phagocytosis: important to clear pathogens and remove damaged or aged endogenous
tissue
- Macrophages are always browsing, in particular close to barriers (e.g., intestine)
- Opsonization as a tag for destruction
o Multiple molecules can function as opsonins (carbohydrate binding proteins or
lectins, CRP, some antibodies, C1q, etc)
- Phagosomes and respiratory burst
INNATE IMMUNITY
Anatomical barriers to infection
- Physical and chemical barriers prevent pathogens from gaining access to deep tissues
o Physical barriers = epithelial & mucosal – block pathogen from entering
o Chemical barriers = antimicrobial substances on skin & acid pH
o When those barriers are breached, innate immune system receptors recognize
the threat
- Aging, dead, or damaged self-structures can also be recognized
- Pattern recognition receptors (PRRs) recognize these structures and target them for
clearance (germ line encoded = less diversity but broad specificity)
Pattern recognition receptors (PRR)
- PRR can be 4 types
o Free receptors in the serum
o Membrane-bound phagocytic receptors (stimulate ingestion of pathogens they
recognize)
o Membrane-bound signaling receptors
o Cytoplasmic signaling receptors
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2
Key elements of innate immunity →
Innate vs adaptive immunity
Anatomical barriers to infection
- Epithelia prevent pathogen’s entry into the
body
o Skin
▪ Thin Outer layer = epidermis –
consists of mostly dead cells filled with
waterproofing protein (keratin)
▪ Thicker inner layer = dermis –
composed of connective tissue, has blood
vessels hair follicles glands and myeloid
leukocytes (dendritic cells, macrophages
and mast cells)
o Mucosal
membranes
Anatomical barriers to infection
- Epithelial layers produce protective substances
o Acidic pH
o Enzymes and binding proteins
o Antimicrobial peptides
- Our skin has anti-microbial substances for certain types of bacteria (gram pos = S.
aureus, E.coli = gram neg)
- Skin secretes psoriasin, an antimicrobial protein that kills E. coli. Fingertips of a healthy
human were inoculated with Staphylococcus aureus and E. coli
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find more resources at oneclass.com
3
Phagocytosis
- Engulfment and internalization of materials (e.g.,
microbes) for their clearance and destruction
- Macrophages,
neutrophils and dendritic
cells in tissues and
monocytes in the blood are
the main cell types that
carry out phagocytosis
- Through various cell
surface receptors the
yercognize microbes such
as bacteria, extend their PM
to engulf them, and
internalize them in phagosomes
- Lysosomes then fuse with the phagocsomes,
delivering agents that kill and degrade the microbes
- Microbes are recognized by receptors on
phagocytic cells called pathogen-associated molecular
patterns (PAMPS)
- The receptors that recognize PAMPs are called
pattern recognition receptors (PRRs)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Victoria richard biol 462 lecture 3: innate immunity. Hematopoiesis is highly regulated: hsc > myeloid progenitor > monocytes, granulocytes, megakaryocyte, erythroid progenitor, dendritic cells, first responders to infections, hsc > lymphoid progenitor > nk, t and b cells, dendritic cells, adaptive immunity. Primary lymphoid organs and microenvironments: bone marrow (site varies among species, thymus (evolutionary conserved) Secondary lymphoid organs (spleen, lymph nodes, malts, peyer"s patches: patrolling phagocytes. Lymphh and lymphatic system sweep antigens from the whole body and present them to the immune. Barriers are the organism"s first line of defense. Phagocytosis: important to clear pathogens and remove damaged or aged endogenous tissue. Macrophages are always browsing, in particular close to barriers (e. g. , intestine) Opsonization as a tag for destruction: multiple molecules can function as opsonins (carbohydrate binding proteins or lectins, crp, some antibodies, c1q, etc) Aging, dead, or damaged self-structures can also be recognized.
