Lecture 9: Innate immunity + antigen presentation

Question 1

Neutrophils role in innate immunity?

Answer 1

Phagocytosis

Promoted by:

1. Receptors for PAMPs (generally weak interactions)
2. Receptors for C3b complement component (complement-mediated opsonsation)
3. Recptors for Fc region of antibodies (immune complex-mediated opsonisation)

Question 2

PAMPs?

Answer 2

Pathogen-Associated Molecular Patters

• Common cell wall structures (Lipopolysaccharides, peptidoglycans)
• Bacterial metabolic products (N-formyl-methionine-peptides)
• Heat Shock proteins (released by stressed cells)

As a group they are referrred to as Immune danger signals.

Dendritic cells (all with varying names) have pattern recognition receptors and release more ‘danger signals’ that enhance immune and inflamation response. = Acute phase proteins

Question 3

Release of acute phase proteins?

Answer 3

• Activated by tissue injury alarm system
• mostly produced by the liver

Actions:

• Promote resolution and repair inflammatory lesions
• limit tissue injury
• Enhance host resistance

Can be used as a quick diagnostic test for inflammation processes.

Question 4

Basic outline of complement system?

Answer 4

Question 5

Lymphocyte circulation and location?

Answer 5

Only about 10% are circulating within the lymph and blood at any one time.

The rest are found within the secondary lymphoid organs:

• Lymph nodes
• Spleen
• Tonsils, adenoids, peyer’s patches (mucosal surfaces)

Question 6

Lymphocyte Subpopulations?

Answer 6

Effectors

• Antibody production (B lymphocutes)
• Antigen-specific cytotoxicity (CD8 T lymphocytes)
• Natural Killer activity (NK lymphocytes)
• Antibody-dependent Cellular cytotoxicity (K lymphocytes)

Regulators

• Cytokine production (CD4 T lymphocytes)
• TH1 (viruses, bacteria, intracellular agents in response)
• TH2 (parasites, allergies, multi-cellular immune response)
• Treg (regulatory T cells - down-regulation response)
• TH17 (Produce interlukin 17 in mucosa and reg. inflammation)

(TH = T helper lymphocyte)

Question 7

Antigen transport and presentation?

Answer 7

Dendritic cells (specialised antigen presenting cells) located all around our body in sites that may encounter antigens. They uptake bacteria, break them down/phagocytose and transport them selves to a local/regional lymph node to present the antigenic shapes to the nodal cells. Recruitment of other cells then occurs.

Question 8

Exogenous and endogenous pathway of presentation?

Answer 8

Exogenous

Specialised antigen presenting cells having phagocytosed antigenic material, class II MHC (HLA-DP, DQ or DR) are used to present the broken down antigen.

Endogenous

Taking antigenic material from within the cell (eg. Viral infection) and breaking up replicating antigens before presenting these antigen parts on Class I MHC (HLA- A, B or C). This happens in normal cells and it is only if something on the inside is changed