Lecture 3: Innate immunity and antigen presentation Flashcards
What are the immune defences (broadly)?
Innate (external): Physical barriers, microbiome, humoral factors i.e enzymes, mucus
Innate (Internal): Early responders, cellular and humoral
Interact with:
Adaptive immunity: Cellular and humoral
To produce inflammation
Where are neutrophils found?
Circulate in blood and infiltrate sites of infection
aka polymorphonuclear leukocytes
Describe phagocytosis:
1) Adherence
2) Membrane activation
3) Phagosome formation
4) Fusion and digestion
5) Release of degraded products
What triggers neutrophil phagocytosis?
- Receptors for common bacterial cell wall components i.e PAMPS: Pathogen associated molecular patterns, DAMPS: Damage associated molecular patterns (weak interaction)
- Receptors for C3b complement component (Complement mediated opsonisation)
- Receptors for Fc region of antibodies
(immune complex-mediated opsonisation)
What are three examples of DAMPS?
Common cell wall structures i.e LPS, peptidoglycans i.e mannans and mannoproteins
Bacterial metabolic products i.e N-formyl-methionine-peotides
Heat shock proteins - Released by stressed cells
These are all immune danger signals
Where are dendritic cells found?
Within the tissue, they have PAMP receptors
When do acute phase proteins peak in their time profile?
Around a week before declining
What are acute phase proteins?
- Activated by tissue injury alarm systems ie danger signals i.e dendritic cells
- Produced mostly by the liver i.e opsonins, coagulation factors, haem and iron binding proteins
What are the actions of acute phase proteins?
- Promote resolution and repair of inflammatory lesions
- Limit tissue injury
- Enhance host resistance
Describe in broad terms the complement system:
Common cell wall components are bound by the first compliment which in turns activates the other compliments that can lead to:
- Opsonisation (enhanced phagocytosis)
- Chemotaxis
- Increased vascular permeability
Describe lymphocyte circulation:
Bone marrow produces lymphocyte precursors and these travel to the thymus and mature. ~10% enter circulation and travel to the secondary lymphoid tissues such as lymph nodes, spleen, tonsils/adenoids/payers patches
The lymphocyte sub-population can be divided into effectors and regulators. Describe the effector cells:
Effectors - B lymphocytes (AB producing), Antigen-specific cytotoxicity (CD8 T cells) -> Subset; NK cells, and ADCC (K lymphcytes)
The lymphocyte sub-population can be divided into effectors and regulators. Describe the regulator cells:
Regulator cells:
- Cytokine production (CD4 lymphocytes)
- Th1 (viruses, bacteria, intracellular agents)
- Th2 (parasites, allergies, MULTICELULLAR)
- Treg (Supressor cells, down regulate)
- TH17 (Mucosa and inflammation)
Dendritic cells are APC cells, what are some examples?
Langerhan cells (SKIN) Alveolar macrophages (Lungs) Kupffer cells (liver) Monocytes (Blood) Epithelial M cells (gut)
What are the APC functions?
- Antigen collection and transport
- Antigen concentration
- Antigen processing
- Present processed antigen to lymphocytes
- Co-stimulation (accessory signals) needed; surface molecules, pro-inflam cytokines
- Tolerance induction
