Immunology Overview Flashcards
Physical and chemical barriers to infection
skin
mucosa
- Resp
- GI
- Genital urinary
Chemical barriers
- Hydrochloric acid
- Lysozyme (Sweat and tears)
Initial response to pathogen invading tissue
- Complement system activation:
- Membrane attack complex destroys pathogen
- C3b is an opsonin
- C5a attracts cells (neutrophils, monocytes and eosinophils)
- C3a,C4a and C5a activate mast cell degranulation
- C3a and C5a activate eosinophil degranulation - Macrophages recognise pathogen and activate innate immune system
- Dendritic cells pick up antigens and begin activating the specific immune system
How do macrophages recognize pathogens?
By binding to pathogen associated molecular patterns (PAMPs)
Macrophage uses various receptors such as toll like receptors
Phagocytosis
Done by macrophages and neutrophils (both phagocytes)
Wraps pathogen in cell membrane creating a phagosome -> phagosomes bind with lysosomes which provide digestive enzymes
If macrophage can’t deal with pathogen alone - will release cytokines (signalling proteins_
Cytokines
Signalling proteins that lead to inflammation
Leads to recruitment of:
- Macrophages
- Monocytes
- Neutrophils
+ inflammatory response
Monocytes
Precursors to macrophages that float around in the blood
- Differentiate into macrophages once they enter tissues
Neutrophils
Another type of phagocyte that circulates in blood and can enter the tissues to destroy pathogens – more specific to bacterial infection
Inflammatory response: (generalised)
- Vasodilation
- Increased vascular permeability
- Mast cell activation and degranulation (releasing further cytokines)
- Activation of clotting system
- Activation of kinin system
Interleukins
Type of cytokine that is released by macrophages and neutrophils – leading to systemic inflammatory response
IL-1
sent to brain to signal fever, reduced apetite and lethargy
IL-6
Sent to liver to prodice Acute phase proteins – act as Opsonins
IL-8
Recruits and activates more neutrophils
IL-2/IL-12
Activates Natural Killer Cells
TNF-α
Does all of IL-1/6/8/2/12 effects
Opsonins
Complex molecules that attach to pathogens and help macrophages and neutrophils to identify them
- Promote phagocytosis
= Example of an opsonin is CRP
CRP
Produced by liver in response to IL-6
Good marker of inflammation/ infection
Complement System
Involves various C1-9 proteins that activate eachother in the complement cascade
- Various products of the complement cascade result in
= Opsonins
=Inflammation
= Destroying pathogens
3 ways of activating complement cascade
- Lectin Pathway
- Alternative Pathway
- Classical Pathway
1+2 - activated directly by pathogens
3 - activated by antibody-antigen complexes (arising from specific immune system)
T + B Cells
Both types of lymphocytes
Comprise the specific immune system
Free to float in blood + lymphatic system
but most are concentrated in:
= Lymph nodes
= mucosa associated lymphoid tissue
Dendritic cells
Antigen presenting cells that travel from site of infection through blood and lymphatics to lymph nodes
- Activates T and B cells
What do dendritic ells present antigens on
HLA Class II molecules
CD4 Cells
Type of T cell
Activated by antigens on dendritic cells (HLA Class II)
Proliferate to become T-Helper Cells
T Helper cells
1# Present antigens on their HLA Class I molecules
- Recognised by CD8 Cells (another type of T Cell)
2# Also release cytokines responsible for:
= making CD8 cells proliferate and differentiate into cytotoxic T cells
= B Cells into proliferating and differentiating into 1# Plasma cells and 2# memory B cells
3# Travel to site of infection and release cytokines responsible for recruitment of monocytes and macrophages to the active tissue
CD8 Cells
Activated by:
- T- Helper cells presenting antigens (HLA Class I)
- Cytokines released by T-Helper cells
Once activated:
- proliferate and differentiate into Cytotoxic T-Cells
