Innate+Defences+(part+2)

=Innate Defences (part 2)=

===Inflammatory Response=== An inflammatory response is triggered whenever body tissues are injured. It works to: 1) Prevent the spread of damaging agents  2) Dispose of cell debris   3) Sets the stage for tissue repair    The four cardinal signs of acute inflammation are redness, heat, swelling, and pain    There are 2 main steps that initiate all other aspects of inflammation
 * Release of chemical mediators
 * Histamine, complement, cytokines among others
 * Phagocyte mobilisation

The mediators function to:

i). Increase blood flow by vasodilatation ® //redness and heat// ® increases the metabolic rate

ii). Increase permeability of local capillaries ® //swelling// (thus //pain// from pressure) ® pressure causes pain ®   but brings in oxygen & nutrients and clotting proteins

iii). Aid in phagocyte mobilization.

Fever
Someone is said to have a fever when their body temperature >37.2 o C   Pyrogens are chemicals (fever producing) secreted by leukocytes & macrophages exposed to bacteria & other foreign substances Pyrogens reset hypothalamic thermostat – think back to homeostasis. If the fever is limited this is considered good If the fever is unlimited or is out of control this is not good
 * increase metabolism and enzyme reactions
 * inhibit microbial multiplication
 * Denature proteins (i.e. enzymes), which means cells wont function as well

Interferons
Interferons are proteins that are produced by the body in response to various stimuli including viruses Genes that synthesize IFN are activated when a host cell is invaded by a virus


 * 1)  Interferon molecules leave the infected cell and enter neighboring cells
 * 2) Interferon stimulates the neighboring cells to activate genes for PKR (an antiviral protein)
 * 3) PKR nonspecifically blocks viral reproduction in the neighboring cell which means the new cells are not infected. This can limit the spread of infection.



(Image taken from: [])

It can also activate macrophages and NK cells.

They are a family of related proteins each with slightly different physiological effects
 * Most other WBCs secrete alpha ( a ) interferon – attract and stimulates Nk’s
 * Fibroblasts secrete beta ( b ) interferon – slows inflammatory response
 * Lymphocytes secrete gamma ( g ) interferon – stimulates macrophages

Complement[[image:ucanaandp/Complement.jpg width="480" height="600" align="right"]]
The complement system consists of 30 or so proteins that circulate in the blood in an inactive form. Complement can be activated by two pathways: **classical** and **alternative.** **Classical pathway** is linked to the immune system. The response depends, in part, on the binding of antibodies to invading organisms Subsequent binding of C1 to the antigen-antibody complexes (complement fixation). **Alternative** pathway is triggered by interaction among factors B, D, and P (not in picture), and polysaccharide molecules present on microorganisms. The two pathways are similar in that: So either way we have MAC formation, and increase inflammation, number of phagocytes and the process of phagoytosis is improved due to opsinisation A pathogen is marked for ingestion and destruction by a phagocyte caused by binding of an antibody to a receptor on the pathogens cell membrane. This causes the phagocytes to be attracted to them. Specific Defences Innate Defences (part 1) Immunity Content
 * Proteins include C1 through C9, factors B, D, and P, and regulatory proteins
 * It provides a major mechanism for destroying foreign substances in the body.
 * Its main job is amplify all aspects of the inflammatory response.
 * Kills bacteria and certain other cell types (our cells are immune to complement).
 * Enhances the effectiveness of both nonspecific and specific defenses
 * Each pathway involves a cascade in which complement proteins are activated in a sequence where each step catalyzes the next
 * Both pathways converge on C3, which cleaves into C3a and C3b
 * C3b initiates formation of a **M**embrane **A**ttack **C**omplex (MAC)
 * MAC causes cell lysis by interfering with a cell’s ability to eject Ca 2+
 * C3b also causes opsonization, and C3a causes inflammation