BB5MOP Week 15

Define pathology and why it is important to understand it.

1. Pathology is the science and cause of disease.

2. Understanding this can impact the diagnosis of disease and what treatments need to be administered.

What is the first line of defence?

The skin and mucus membrane.

What mechanisms do the skin and mucus membrane have?

Sweating, tears and enzymes to break down bacteria.

What kills the pathogen directly?

Antimicrobial peptides

How does the microbiome in the gut work?

They crowd out the harmful microbes, so there isn't enough space for pathogens to grow.

What is the next line of defence, if the pathogens make it past the first line of defence?

Innate immune system

Describe the innate immune system.

It is less specific, produces a general response and does not target a specific pathogen.

What are complement proteins?

A cascade of proteins that circulate in the blood, when activated they tag pathogens for opsonisation and destruction by immune cells.

How can complement directly kill pathogens?

Complement can form a membrane attack complex (MAC), which forms pores in the membranes of the pathogens destroying them.

What are the first responders when pathogen infect?

Neutrophils, they rush to the site of infection and engulf the pathogen.

What immune cells remove the pathogen, following the neutrophils attack on the pathogen?

Macrophages, they phagocytose the neutrophils containing the pathogen and destroy them via apoptosis.

What are cytokines and what do they do?

1. Cytokines are the communicating signals of the immune system.

2. They release other immune cells and aid in coordinating the immune response.

What else do cytokines do?

They promote inflammation, which brings more immune cells to the area of infection to contain it.

What is the third line of defence, if the pathogen passes the second line of defence?

Adaptive immune system

Describe the adaptive immune system.

It is highly specific at targeting specific pathogens infecting the body.

What is the adaptive immune system activity based on?

Based on the activity of the lymphocytes, which are B and T cells.

What is an important key feature of lymphocytes?

They are equipped to recognise a specific type of antigen.

How is the pathogen's antigen recognised?

It is recognised based on gene arrangement, where the body will shuffle the genetic codes to recognise any pathogenic threat.

What is gene rearrangement?

A massive library of variant receptors that are on the surface of the B and T cells.

What are the two main branches of T cells?

CD8+ T cells and CD4+ T cells.

Describe CD8+ T cells.

1. They are cytotoxic T killer cells.

2. Release perforins that punch holes in the pathogen's membrane to destroy them.

How do CD8+ T cells fully get rid of pathogens?

They activate apoptosis, which is the programmed cell death of unwanted cells, directly killing the pathogen.

Describe CD4+ T cells.

1. They are T helper cells.

2. They release cytokines that stimulate recruitment of more immune cells to the site of infection, indirectly killing the pathogen.

Why are CD4+ T cells important?

They release more immune cells such as neutrophils and macrophages that strengthen the CD8+ T killer cells action.

What can B cells recognise?

Recognise native antigens directly.

How is the B cell response strengthened?

Reinforcement from T cells makes the response more effective and lasts longer.

What happens when the immune system malfunctions?

Causes autoimmune diseases and allergies.

Define autoimmunity.

Where the immune system mistakenly attacks human self-antigens.

Give three examples of autoimmune diseases.

1. Rheumatoid arthritis (RA)

2. Lupus

3. Hashimoto's disease

What is rheumatoid arthritis?

Immune system attacks the lining of the joints, causing pain and inflammation that can damage the joints.

What is lupus?

Systemic disease that can attack multiple areas of the body such as, the kidney and heart.

What is Hashimoto's disease?

Immune system attacks the thyroid gland, so less not thyroid is made.

What is an allergy and give three examples of allergens?

An overactive immune response to something that isn't harmful, like pollen, dust mites and certain foods.

What is the term used to describe an antigen that isn't harmful?

Innocuous antigens

What is the overreaction in an allergy caused by?

Often caused by IgE response.

What happens when IgE binds to the allergen?

Binding triggers the activation of mast cells to degranulate and release histamines and other inflammatory mediators.

How are allergies thought to develop?

Combination of both genetics and environment.

Give three examples of diagnosis for autoimmunity and allergies.

1. Phagocytosis assays

2. Antibody titres

3. Flow cytometry

Describe phagocytosis assays.

Determines how much phagocytosis is happening and if the macrophages are doing their job of engulfing pathogens.

Describe antibody titres.

Counting the number of specific antibodies in the blood can indicate if the immune system is working.

Describe flow cytometry.

Quantifying the amount of super specific cells like CD8+ and CD4+ T cells, measures how active cells are.