L1 + L2 (overview lectures) Flashcards by Nicky Scher

How is a properly functioning immune system defined?

(1)
- distinguishes between SELF and NON-SELF
- will only mount a response against NON-SELF
- WILL mount a response against a pathogenic bacteria
- Will NOT mount a response against a self-protein

(2)
- distinguishes between DANGEROUS non-self and SAFE non-self
- WILL mount a response against a pathogenic bacteria
- Will NOT mount a response against a dog
- Will NOT mount a response against commensal bacteria

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What happens when a properly functioning immune system breaks down?

A dysregulated immune response.
might respond to safe non-self (e.g. allergies)
might respond to self (e.g. autoimmune disorders)

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What does the immune system fight?

Pathogens
Immune responses are quickly tailored to the type of microorganism involved.

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What are the four major categories of pathogens?

1) Virus: rotavirus
2) Parasite: Filaria
3) Bacterium: Mycobacterium tuberculosis
4) Fungus: Candida albicans

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Why do different pathogens require different immune responses?

Because pathogens vary in location and structure, leading to different types of immune mechanisms.

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What is a major difference between types of pathogens in terms of immune response?

Pathogens can be intracellular (e.g., viruses) or extracellular (e.g., bacteria), which affects how the immune system responds.

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How does the immune response differ between intracellular and extracellular pathogens?

Intracellular pathogens (like viruses) require a different immune strategy compared to extracellular pathogens (like bacteria), which impacts the type of immune cells and molecules involved.

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What makes the immune response complex?

It involves many different molecules, cells, and tissues working together over time and in different body locations.

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Can the immune system result in life-long immunity?

Yes, in some cases, the immune system can create long-lasting immunity after responding to a pathogen.

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In response to pathogens, immune systems use two interconnected systems. What are they?

1) Innate immunity - First line of defence, fast but non-specific.

2) Adaptive immunity - Highly diverse and specific.

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What are the major players in the immune system?

1) Key organs and tissues
2) Cells
3) Molecules

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What is the immune system?

The immune system is a collection of organs, tissues, cells, and molecules that work together to protect the body from infection.

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What are the key components of the immune system?

1) Bone marrow
2) Thymus
3) Lymphatics (lymphatic system)
4) Lymph nodes

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How do immune cells travel in the body?

Immune cells travel in the body and occupy different tissues over time.

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What are Primary (CENTRAL) Lymphoid organs?

where immune cells are generated:
bone marrow
thymus

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What are secondary (PERIPHERAL) lymphoid organs?

where immune cells are activated:
lymph nodes
spleen
mucosal associated lymphoid tissues (malt)
other diffuse and loosely organized areas

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How are primary and secondary lymphoid organs connected?

via blood and lymphatic circulatory systems.

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What are the two categories that different immune cells are associated with?

1) Innate
2) Adaptive

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What are immune cells generally known as? Where do they originate?

generically known as leukocytes or white blood cells.
originate in bone marrow.

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Where do mature blood cells arise from?

A single cell type, the hematopoietic stem cell (HSC).

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What is Hematopoiesis?

the process by which HSCs differentiate into mature blood cells.
occurs in the bone marrow.

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Pluripotent

Stem cells can generate almost
every specialized cell type in an organism

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Multipotent

Stem cells generate various
cell types in a family of related cells

What are the two main lineages of immune cells?

1) Lymphoid: includes B cells, T cells, and NK cells

2) Myeloid: includes most other leukocytes

Which cells can be generated from both lymphoid and myeloid lineages?

Dendritic Cells

Where do immune cells go after being generated?

They either: 1) Reside in tissues and organs 2) Circulate in the blood or lymphatic system

What cells are part of the myeloid lineage?

- Red blood cells (erythrocytes) - Granulocytes: Neutrophils, Eosinophils, Basophils/Mast cells. - Megakaryocytes. - Monocytes.

What is the role of red blood cells (erythrocytes)?

Red blood cells carry oxygen to cells and tissues and can generate antimicrobial compounds.

What are the functions of granulocytes?

1) Neutrophils: Direct harm to pathogens 2) Eosinophils: Antiviral and anti-parasitic activity 3) Basophils/Mast cells: Inflammation and allergies

What do megakaryocytes give rise to?

Platelets (blood clotting)

What is the role of monocytes?

Monocytes migrate into tissues and differentiate into macrophages, which repair/remodel, destroy pathogens, and present antigens.

What is the function of macrophages, immature dendritic cells, and neutrophils?

They are specialized for phagocytosis (cellular uptake by engulfment).

How do macrophages present antigens?

Macrophages can present antigens to T cells after phagocytosis.

What is the role of immature dendritic cells?

Immature dendritic cells capture antigens, mature, and migrate to present antigens to T cells.

Why are dendritic cells important?

Dendritic cells are the most potent antigen-presenting cells for activating naïve T cells.

What are the three main types of cells that develop from the common lymphoid progenitor?

1) B lymphocytes (B cells) 2) T lymphocytes (T cells) 3) NK cells (innate lymphoid cell subtype) & ILCs

How do lymphocytes differ from one another?

Lymphocytes appear similar, but they carry different sets of clusters of differentiation (CD) molecules on their surface. (ex., CD4 vs CD8)

What is the role of T and B cells in immunity?

T and B cells are responsible for adaptive immunity, generating responses that are highly specific.

How is specificity determined in T and B cells?

Specificity is determined by the expression of receptors on the cell surface.

What receptor do B cells express?

B cell receptor (BCR), which can be bound to the membrane or secreted as antibodies.

What receptor do T cells express?

T cell receptor (TCR), which is membrane-bound.

What role do dendritic cells play in the immune response?

Dendritic cells are key in detecting infection and activating adaptive immunity. Key bridge in immune response!

How do innate and adaptive immunity work together?

Innate and adaptive immunity work cooperatively. Activation of innate immune responses produces signal molecules that stimulate and direct adaptive immune responses.

What functions do immune system molecules have?

Molecules in the immune system can: 1) Communicate between cells or inside cells 2) Mediate interactions between cells 3) Trigger changes in target cells (e.g., activation, signaling, migration, transcription, differentiation)

What are the key types of molecules in the immune system?

1) Secreted proteins 2) Receptors on the cell surface 3) Intracellular signaling molecules & transcription factors 4) Antigens

What are secreted proteins in the immune system?

Secreted proteins include cytokines and chemokines: --> Cytokines: Messenger proteins secreted by certain cells. --> Chemokines: A subset of cytokines that recruit specific cells to a site.

How do cytokines and chemokines interact with cells?

Cytokines and chemokines bind to target cells via specific receptors, allowing cells to interact with each other.

What are intracellular signaling molecules and transcription factors?

Intracellular signaling molecules and transcription factors are involved in signaling within the cell in response to stimuli, influencing various cellular processes.

What is an antigen?

An antigen is a molecule that immune responses are generated against.

What is an example of Molecules mediating actions/changes?

Cells interact with each other via receptors, resulting in a change (cell migration). 1) monocyte binds adhesion molecules on vascular endothelium near site of infection and receives chemokine signal. 2)the monocyte migrates into the surrounding tissue. 3)monocyte differentiates into the inflammatory monocyte at site of infection.

What is an antigen?

An antigen (Ag) is any specific molecule that can trigger an immune response.

What types of molecules can be antigens?

Antigens can be: Protein (most common) Nucleic acid Polysaccharide Lipid Organic chemicals Drugs

What is an epitope?

An epitope is the specific portion of an antigen that is recognized by a receptor on an immune cell.

What are the steps of innate immune response?

1) Pathogen entry. 2) Pathogen recognition. 3) Inflammation. 4) Homing to LN.

What are the steps of adaptive immune response?

1) T & B cell activation. 2) Adaptive immune response. 3) Regulation & memory.