Immune System 1 Flashcards by Hadiyah Qureshi

What is immunology?

Physiological mechanisms that defend the body against invasion from other organisms

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What is an immunogen?

A molecule that stimulates the immune system to produce a response.

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What is an antigen?

The part of the immunogen that reacts with immune effector cells or soluble antibodies.

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What is an epitope?

The part of the antigen that reacts with immune effector cells or soluble antibodies

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Define pathogen

Any organism with a potential to cause a disease

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State the 4 main types of pathogens.

Bacteria
Viruses
Fungi
Parasites i.e worms

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Name the process by which white blood cells are generated.

Haematopoiesis

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What do potent haematopoietic stem cells differentiate into?

Two types of progenitors - the common lymphoid progenitor and the common myeloid progenitor

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State the myeloid cells classification.

1) Granulocytes - neutrophil, eosinophil, basophil
2) Antigen presenting cells - monocytes, macrophages, dendritic cells
3) Mast cells

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State the lymphoid cells classification.

1) Small lymphocytes - B cells and T cells
2) Large lymphocytes - NK cells

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State the primary lymphoid organs.

Bone marrow
Thymus

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State the secondary lymphoid organs.

Spleen
Adenoids
Tonsils
Appendix
Lymph nodes

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What are the primary lymphoid organs involved in?

Generation and maturation of beta cells, T cells and immune cells

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What are the secondary lymphoid organs involved in?

Attacking the pathogen

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Describe the role of the bone marrow.

B cells originate and mature in it
T cells originate in it but leave at an immature stage

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Describe the role of the thymus.

Immature T cells migrate here to complete their maturation
As they differentiate they progress from the cortex into the medulla

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Describe the role of secondary lymphoid tissues.

They are the sites where mature lymphocytes are activated to respond to invading pathogens.

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Where are lymphatic vessels?

In the connective tissues throughout the body.

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What is the role of lymphatic vessels?

They collect the plasma fluid that continually leaks out from blood vessels.

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Where are lymph nodes located?

At the junctions of a network of lymphatic vessels.

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What is the fluid inside lymphatic vessels called and how is it returned to the blood?

Lymph - via the thoracic duct

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Describe how lymph nodes fight against pathogens during infection. (4)

Arriving lymphocytes segregate in different areas of the lymph node
Pathogens are drained in lymph nodes from the afferent lymphatic vessels where they are trapped by dendritic cells and macrophages
B and T cells encounter the pathogen and are activated and undergo clonal expansion and differentiation.
As the lymphocytes grow in number, the lymph node increases in size (swollen glands)

What are Mucosa Associated Lymphoid Tissue?

Specialised tissues that are distributed in submucosal layers of the gastrointestinal, genital, respiratory and urinary tracts.

What are the two types of immunity?

Innate
Adaptive

Describe innate immunity

- Rapid response (no memory) - Fixed response - Limited specificity - Constant during response

Describe adaptive immunity.

- Slow response (memory) - Variable - Highly specific - Improve during response

Which cells are involved in innate immunity?

- Neutrophil - Eosinophil - Basophil - Monocytes

If the cells in innate immunity cannot kill the pathogen what happens?

Activates the adaptive immunity.

Which cells are involved in adaptive immunity?

B cell T cell

What three things are involved in the immediate innate response

- Barriers - Antimicrobial peptides - Complement system

What is the role of physical and chemical barriers?

To prevent pathogens from crossing epithelia and colonising tissues

State the mechanical barriers for the skin.

- Epithelial cells joined by tight junctions - longitudinal flow of air or fluid

State the chemical barriers of the skin.

- Fatty acids - Antibacterial peptides

State the microbiological barriers of the skin.

Normal flora - bacteria that live in our body that do not cause harm which compete with foreign pathogens.

State the mechanical barriers in the gut.

- Epithelial cells joined by tight junctions - Longitudinal flow of air or fluid

State the chemical barriers of the gut.

- Low pH - Enzymes (pepsin) - Antibacterial peptides

State the microbiological barriers of the gut.

Normal flora

State the mechanical barriers of the lungs.

- Epithelial cells joined by tight junctions - Movement of mucus by cilia

State the chemical barriers of the lungs.

Antibacterial peptides

State the mechanical barrier of the eyes/nose

Epithelial cells joined by tight junctions.

State the chemical barriers of the eyes/nose

- Salivary enzymes (lysozyme)

What are anti-microbial peptides?

Molecules sensitised from immune cells which circulate in the blood and fight against fungi, bacteria and viruses

What is the complement system?

- Group of nearly 30 serum and membrane proteins - Activated upon infection - Mechanism = ezymatic cascade

Describe the 4 roles of the proteins in the complement system?

1) Bind covalently to bacteria + which are then phagocytosed by cells with complement receptors - Recruit phagocytes to the site and regulate inflammatory response - Some produce B cells - Terminal component of system generates Membrane Attack Complex (MAC) - results in lysis of pathogens

State the four responses of the induced innate immune system.

- Phagocytosis - Cytokineses production and inflammation - Toll Like Receptors activation - NK cells

What are the two main phagocytic cells?

- Neutrophils - Mononuclear phagocytes (monocytes and macrophages)

Describe neutrophils.

- Short-lived cells - Multi-lobed nucleus - Abundant in sites of acute inflammation

Describe mononuclear phagocytes.

- Longer lived cells - Antigen presenting cells

State the three stages of phagocytosis.

1) Recognition and attachment 2) Engulfment 3) Killing and degradation

Describe the recognition and attachment stage of phagocytosis.

- Different types of receptors - Opsonin receptors enhance efficiency of phagocytosis as phagocytes have high-affinity with opsonin proteins

Describe the engulfment stage of phagocytosis.

- After a particle is bound to phagocyte receptors, the plasma membrane forms a vesicle that encloses the particle - Phagosome then fuses with a lysosomal granule

Describe the killing and degradation stage of phagocytosis.

Lysosomal enzymes released

What are cytokines

Low molecular weight protein which are secreted by cells that stimulate o inhibit the activity, proliferation or differentiations of other cells

Describe the three roles of cytokines

1. Mediators and regulators of innate immunity - produced by mononuclear phagocytes in response to infectious agent 2. Mediators and regulators of adaptive immunity - produced by T lymphocytes in response to specific recognition of foreign antigens 3. Stimulators of haematopoiesis - produced by bone marrow stromal cells, leukocytes and other cells and stimulate the growth and differentiation of immature leukocytes.