Lecture 1 - Innate vs. Adaptive; Pattern Recognition (Bailey) Flashcards by Kellie Willis

What is infection?

Invasion of the body by a microbe that causes damage either directly or indirectly.

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What are the 6 steps of infectious disease?

Encounter (w/ pathogen)
Entry (into body)
Colonization and/or Invasion
Multiplication and/or Spread
Damage
Outcome

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Does encounter = infection?

NO!

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Nonspecific Adherence (of a pathogen to a surface)

reversible
docking
examples: random interaction, electrostatic attractions, etc.

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Specific Adherence (of a pathogen to a surface)

Irreversible
Anchoring
Involves ADHESINS

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What are adhesins?

Adhesins are involved in SPECIFIC ADHERENCE. They are on the surface of microbes.
They bind to adhesin receptors, which are very specific.
Example: Strep. mutans uses GLUCOSYL TRANSFERASE as an adherin

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What are the two mechanisms of “spread?”

LATERAL PROPOGATION to continuous tissues
- multiply then spread
DISSEMINATION to distant sites
- spread then multiply

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Is DAMAGE necessary for a microbe to be considered a pathogen?

Yes

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What is the principal physiological role of the immune system?

To protect the organism from infectious microbes.

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What are some PHYSICAL BARRIERS of INNATE IMMUNITY?

epithelial surfaces (skin)
mucosal surfaces
flushing action of tears and saliva

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What is a CHEMICAL BARRIER of INNATE IMMUNITY?

ANTIMICROBIAL PEPTIDES (AMP)

 - present on mucosal surfaces, skin, etc. 
 - 45 AMPs in saliva alone 
 - tend to be cationic (pathogens are anionic)

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Name 4 AMPs and their function.

Lysozyme - cleaves peptidoglycan; active against gram + bacteria
Cathelicidin - disrupts bacterial membranes
Defensins - creates pores in microbes
Lactoferrin - sequesters iron that bacteria need to survive

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What is a MICROBIAL BARRIER of INNATE IMMUNITY?

Microbiota

 - outnumbers cells of the body 10:1
 - outnumbers human genes 100:1

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What 2 categories are leukocytes divided into?

Innate Cells
- first responders
- non-specific
Adaptive Immune Cells
- respond later
- specific
- MHC restricted

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Where to INNATE immune cells come from?

Myeloid cells

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Where to ADAPTIVE immune cells come from?

Lymphoid Cells

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What are the cells of the INNATE immune system?

Monocytes/Macrophages
Neutrophils
Dendritic Cells
Other Granulocytes
- eosinophils
- basophils
- mast cells
Natural Killer Cells

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Main role of Eosinophils?

parasitic infections (recognizes IgE-coated parasites)

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Do neutrophils present antigens?

No, they just kill.

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Which cells of the innate immune system are great antigen-presenting cells?

Monocytes/Macrophages and Dendritic cells

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How are monocytes and macrophages different?

Monocytes - in circulation

Macrophages - in tissue

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What are the 3 important function of macrophages?

Kill
Present Antigen
Produce cytokines

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What cell of the innate immune response has a multi-lobed nucleus?

Neutrophil aka Polymorphonuclear Cell (PMN)

-granulocyte

What is the main function of a neutrophil?

Kill

What is the main function of a dendritic cell

Antigen presentation

What is the PRINCIPAL cell type that LINKS the innate immune response to the adaptive immune response?

Dendritic Cell

What are the cells of the ADAPTIVE immune response?

B cells T cells Natural Killer Cells

Where do B cells mature?

bone marrow

Where to T cells mature?

Thymus

Where to the cells of adaptive immunity come from?

Common LYMPHOID progenitor

What are the two components of ADAPTIVE immunity?

1. Humoral Component - B cell mediated 2. Cell-Mediated Component - T cell mediated

What are the two types of T-cells, and what do they do?

1. Helper T-cells (produce cytokines that attract, activate, and inactivate leukocytes) 2. Cytotoxic T-cells (kill virally infected cells and tumor cells)

Which MHC to CD4+ (helper) T-cells recognize?

MHC II

Which MHC to CD8+ (cytotoxic) T-cells recognize?

MHC I

Where are cell of the adaptive immune system activated?

within lymph nodes

How are T and B cells activated in a lymph node (LN)?

1. microbe infects host 2. microbe is taken up by APC @ site of infection 3. APC enters lymph circulation and into LN 4. Naive T and B cells enter LN from circulation

What is a Pathogen Associated Molecular Pattern (PAMP)?

PAMPs are unique structures on microbes (that often involve repeated structures) that are recognized by INNATE immune cells.

What is an example of a PAMP on Gram Negative bacteria?

Lipopolysaccharide (LPS) contains repeated sugars that can be recognized by pattern recognition receptors (PRR) on innate immune cells.

What is an example of a PAMP on Gram Positive Bacteria?

Murein and teichoic acids contain repeated sugars that can be recognized by pattern recognition receptors (PRR) on innate immune cells.

What is a Pattern Recognition Receptor (PRR)?

Receptor that cells of the INNATE immune system use to recognize Pathogen Associated Molecular Patters (PAMPs) on microbes.

Name a key PRR on innate immune cells.

Toll-like receptor (TLR)

Which type of bacteria does TLR2 recognize?

Gram +

Which type of bacteria does TLR4 recognize?

Gram -

What do extracellular surface TLRs recognize?

PAMPs

What do INTRAcellular endosomal TLRs recognize?

things that are found in endosomes after phagocytosis (such as nucleic acids)

Do TLRs only have to do with innate immune cells?

TLRs are only found on innate immune cells, but the consequences of TLR litigation affect BOTH innate and adaptive immunity.

What do cells of the adaptive immune system recognize?

antigens

What is an antigen?

any substance that can be SPECIFICALLY bound by a cell of the adaptive immune system

What is an immunogen?

an antigen that elicits an immune response

What is a Tolerogen?

an antigen that induces immunological tolerance of immune non-responsiveness.

What is an Allergen?

an antigen that causes an immediate hypersensitivity (allergic) reaction

T-cells are MHC restricted. What does this mean?

They cannot recognize antigen alone. It must be presented by MHC.

B-cells are NOT MHC restricted. What does this mean?

B cells can be directly activated by antigen. | However, T cells are often needed.

What are some important receptors for INNATE immunity antigen recognition?

1. Toll-like receptors (TLR) 2. N-formyl-methionyl receptor 3. mannose receptor 4. scavenger receptor

What are the two types of antigen-specific receptors of the ADAPTIVE immune system?

B cell receptor (Ig) -recognizes solubue intact macromolecules and small chemicals T cell receptor (TCR) -ONLY recognizes processed antigen fragments presented by MHC on the surface of antigen presenting cells (APCs)