Innate immune system lecture Flashcards
Specificity & Memory
Specificity – Innate response lacks specificity Memory – Innate response lacks memory – Innate immune response blocks 99.9% of microbial attempts to infect human body.
First line of defense are barriers that shield interior of body from external surroundings
- Anatomical barriers include?
skin and mucous membranes
– Provide physical separation
– Membranes bathed in antimicrobial secretions
Normal Microbiota
– Defined as microorganisms found growing on body surfaces of healthy individuals body surfaces of healthy individuals – Not technically part of immune system * However, provides significant protection – Protects through competitive exclusion * Covers binding sites – Pathogens can’t bind * Competes for nutrients – Nutrients unavailable for pathogens
Neutrophils
Most abundant and important in innate response
– Sometimes called polymorphonuclear neutrophilic leukocytes (PMNs)
Basophils
Involved in allergic reaction
Eosinophils
Important in expelling parasitic worms
– Active in allergic reactions
Mononulcear phagocytes
Constitute collection of phagocytic cells called mononuclear phagocyte system
– Include monocytes
* Circulate in blood
* Macrophages differentiate from monocytes
– Present in most tissues
* Abundant in liver, spleen, lymphnodes, lungs and peritoneal cavity
Dendritic cells
Branched cells involved in adaptive immunity
– Function as scout in tissues
* Engulf material in tissue and bring it to cells of adaptive immunity
Lymphocytes
Involved in adaptive immunity – Two major groups 1) B lymphocytes – B cells 2) T lymphocytes – T cells – Another type 3) Natural killer – Lacks specificity of B and T cells
In order for immune system to respond, cells must
communicate with environment and with each other
- Cell surface receptors are the “eyes” and “ears” of the cell
- Cytokines are the “voice”
- Adhesion molecules act as the “hands”
Surface receptors are?
– Membrane proteins to which signal molecules bind
– Receptors specific to molecule to which it bonds
* Binding molecules called ligands
– When ligand binds, receptor becomes modified and sends signal to cell
* Cell responds by initiating some action
Cytokines are
bind to surface receptors and regulate cell function
– Numerous cytokine classes
1) Chemokines – important in chemotaxis important in chemotaxis
– Enhance ability of cells to migrate to appropriate site in body
2) Colony stimulating factors – Important in multiplication and differentiation of leukocytes
– During immune response, directs immature leukocytes to correct maturation pathway
3) Interferons – important in control of viral infections
– Also associated with inflammatory response
4) Interleukins – produced by leukocytes
– Important in innate and adaptive immunity
5) Tumor necrosis factor – kill tumor cells
– Instrumental in initiation of inflammation
Adhesion molecules are
– Allow cells to adhere to each other
– Responsible for the recruitment of phagocytes to
area of injury
* Epithelia cells lining blood vessels produce adhesion
molecules that catch phagocytes as they pass by
– Cause phagocytes to slow and leak out of vessels to area
of injury
Toll-like receptors (TLR) and NOD proteins
– Pattern recognition receptors
– TLR allow cells to “see” molecules signifying presence of microbes outside the cell
– TLR found in variety of cell types
* Recognize distinct “danger” compounds
– Signal is transmitted
* Results in change of gene expression of cell
– NOD proteins do same for inside cell
Complement system is composed of
nine proteins
- C1 – C9
– Numbered as discovered, not order of activation
* Certain proteins split into “a” and “b” fragments after
activation
– C3 can spontaneously split to C3a and C3b
* Insures enough C3b for activation of alternative pathway
– Activation of complement leads to major protective
outcomes
1) Inflammation
2) Opsonization
3) Lysis of foreign cells
