Innate immunity Flashcards
Two key aspects for an oragnisms survival - and the place of the immune system
1) Ability to self replicate (autopoiesis)
2) Adapation - coherence between internal and external environments.
The immune system (along with the nervous system) help to maintain internal-external coherence
Innate, adaptive, and inflammation
The innate immune system is made up of a physical and microbial portion, and a cellular/hormonal portion. Adaptive immunity is just cellular and hormonal.
The innate and adaptive immune system directly regulate each other, but they may also interact through inflammation.
Adaptive vs innate
Adaptive
Generally activated later, antigen-specific, results in immunological memory
Innate
generally activated first, has no memory of past infections, and is not antigen specific
External surface protection (innate immune) biochemical vs biophysical defenses
Biophysical
Skin, mucus, cilliary lining, stomach acid
Biochemical
Lysozyme in salvia and tears, sebaceous gland secretions, commensal organisms in gut and vagina, spermine in semen
Internal innate factors
Phagocytosis
Neutrophils have the ability to identify bacteria, ingest them, and destroy them
Complement
The complement system can be activated in 3 ways. Classical pathways (from antigen-antibody complexes), lectin pathway by sugar moeities on bacteria, or the alternative pathway (activated by many things)
These three pathways converge at C3. once this molecule is created, a subsequent clevage cascade of complement factors causes the creation of C3a, C4a, and C5a which all work to increase vascular permeability (aiding neutrophil extravasation).
C3a also acts as a cehmotaxic agent, whereby its origin of production has high levels, and as it diffuses away it creates a concentration gradient, which cells will follow.
C3b can opsinise bacteria, which enhaces phagocytosis
The lymphatic system.
A network of vessels that drain excessive interstitial fluid that isn’t reabsorbed by the venous sytem, and delivers it back to the venous system via the subclavian veins
It consists of lymphatic vessels, which are connected to lymph nodes (that act as the filtration units).
Lymphatic vessels are endothelial cells that have gaps allowing interstitial fluid through them. They don’t collapse thanks to anchoring filaments.
Blocking lymphatic vessels
Cancer often requires surgical removal of surrounding lymphatic vessels/nodes to prevent metastasis of cancer through them. This can cause lymphodema.
Can also be caused by parasites, like the microfilaria parasitic worms - they reside int helymphatic vessels, causing injury and damage, leading to scarring which blocks the ducts.
Lymphoid organs
Primary organs
These are the organs where the lymphoid cells are first made. The thymus for T cells, and the bone marrow for B cells.
Secondary organs
The place where the newly developed cells go. Including lymph nodes, peyers patches, appendix, adenoids, and the spleen.
These can be thought of as filtration untis of the lymphatic system.
The lymph nodes filter tissue, the spleen the blood, and peyers patches the gut.
The lymphatic vessels (along with blood vessels) help to bring in pathogens and antigens, and take out immune effectors to bring them towards tissue. .
The lymph nodes are organised roughly into T cell,B cell, and Macrophage rich areas, but will all collaberate with each other to generate an immune response.
Antigen transport
A breach in the skin will allow pathogens in .
Dendritic cells within the tissue (like langerhangs in the skin) will phagocytose pathogen and present its antigens on its surface.
Dendritic cell will then be transported through the lymphatics into the lymph nodes, where the antigen on its surface will be presented to adaptive immune cells that are specific for this antigen.
This initiates an antigen-specific response and recruitment of cells to fight pathgoen.
