Adaptive immune system

Name the cells of the adaptive immune system

• T helper cells (CD4+)

• Cytotoxic T cell (CD8+)

• B cells

• Natural killer cells

Process of activating CD4 and CD8 cells

1. Dendritic cells phagocytose pathogen and exhibit antigen from them on MHC II molecules → find CD4+ cell in lymph node that recognises antigen and is activated

2. T cell interact with B cells and they mature into plasma cells

3. The T cell produces cytokines that cause proliferation of CD8 + cells

4. CD8+ cells recognise antigen presented on MHC I molecules

How do cytotoxic T cells kill a virus?

Kill it directly

Induce apoptosis through the activation of Fas molecule

What do T cells originate from and where do they mature and how does it happen?

Haemogapoietic stem cells (HSC) in the bone marrow

Mature in the thymus

T cell receptor CD3 has alpha and beta regions which undergo rearrangement to produce a receptor specific to an antigen

What is the process of T cell maturation which means we don’t recognise “self” cells?

1. Lymphoid progenitor cells enter the outer cortex of the thymus

2. T cells migrate through the thymus and present CD4 and CD8, leading to a double-positive cell

3. The Double positive cell interacts with corticol / thymic epithelial cell, recognising either MHc1 or MHc2 (If they don’t interact, they die)

4. Depending on which one was recognised, they commit to CD4 or CD8 and pass to the medulla (if recognised by a dendrite cell by displaying self antigen, they die)

How does a T cell activate a B cell?

1. B cell encounters and antigen, internalises it and presents it on MHC II

2. An activated T cell secretes more IL2 (T cell Growth factor) Causing an expansion of the T cell population that recognise the antigen

3. T cell bind to the B cell activating it

What immunoglobulin increase after a

1. First infection

2. Infection they had before

1. IgM

2. IgG

Where are the antibodies IgA , IgE and IgD found?

A: secreted into mucus, tears, saliva

E: secreted when allergic reaction/ parasitic activity

D: B cell receptor

What Is an opsosonin?

A molecule that can attach an antigen to the surface of a bacteria/ virus infected cell

What happens to memory cells?

1. They proliferate and become effector cells and combat the infection

2. They don’t proliferate and stay in the spleen

Name some live attenuated vaccines

MMR

flu

Polio

Name some killed/ inactivated vaccines

Polio (Salk)

Influenza

How do natural killer cells kill a cell?

1. they are activated by cytokines released from macrophages

2. Interact with Fas Ligand (FasL) on the T cell surface with Fas on the surface of the infected cell

3. release interferon gamma which activates macrophages resulting in an inflammatory response

4. Secrete perforin and granzyme→ make pores in infected cell membranes