Lecture 15: the immune system hero or villain ?

Why is the immune system a hero

• Essential for defence against microbes

What happens when the immune system malfunctions

• Autoimmunity

• Immune deficiency

Basics of innate immunity

• Immediate

• Effective

• Inefficient

• Amnesic

What do mast cells release

• Histamine

• Hormonal mediators

• Cytokines

What do basophils release

• Histamine

• Cytokines

What innate cells initiate allergy

Basophils via cytokine production; They act as APC’s which activate naive CD4 cells to develop into Th2 cells

Role of natural killer cells

• Innate defence cells

• Destroy tumor & infected cells

• Induce apoptosis (cytotoxic)

Roles of eosinophils

• Anti-parasitic activity

• Produce cytokines

• Phagocytosis

Th1 cells

• Activate T cells & facilitates their growth

• Immune activation of macrophages

• Intracellular microbes

• stimulate cellular immune responses

• produce cytokines

Th2 cell

• Produce cytokines

• Promotes growth and proliferation of bcells, mast cells & eosinophils

• Extracellular pathogens

• Cellular immunity

• Associated with Asthma and Allergy

Th 17 cell

• subset of CD4 helper T cell

• Involved in Autoimmune disease

• Promote neutrophil recruitment

• Mucosal immunity

• Maintains mucosal barriers

iTreg & nTreg cells

• Prevent adverse immune activation

• essential for Immune tolerance

5 monogenic causes of multiple autoimmune endocrine disease

1. AIRE

2. FOXP3

3. LRBA

4. STAT1

5. STAT3

What is the main feature of asthma

Inflamed air tubes

What is diabetes mellitus an example of

Organ specific autoimmune disease

Types of immune deficiencies

1. Autoinflammation & monogenic autoimmune disease - FMF, CAPS

2. Allergy - asthma, hay fever

3. Organ specific immune disease - T1D

4. Immune mediated inflammatory disease - Rheumatoid arthritis

5. Overactive immunity - severe COVID 19 with hyperinflammation

Histamine role

promote vasodilation of blood vessels and increase their permeability as well as promoting inflammation

Cytokines

signalling molecules which attract more phagocytes to sites of infection