Ch.22 Immune System Flashcards
Infectious agents
Or (pathogens) cause damage or death to a host organism
Function of the immune system
Protection from infectious agents and harmful substances
Prions
Structure:
an abnormal form of a normally harmless protein found in the brain
Features:
Upon entering a healthy organism, it induces existing, properly folded membrane proteins to convert into the disease-associated, prion form.
Diseases:several fatal diseases of nervous tissue
Viruses
Structure:
Not cells. Composed of a nucleic acid within a cuspid (protein coat), some have a lipid envelope. Small
Features:
Obligate intracellular parasites (must enter cells to reproduce).
Destroy cells when newly formed viruses exit
.
Diseases:
common cold, chicken pox, HIV, warts
Bacteria
Structure:
Unicellular prokaryotes
Features:
Living organisms that require nutrients to survive.
When invade other organisms–cause damage by
destroying tissues or toxin release
Diseases:
staph, infection, tuberculosis(TB), Lyme disease
Protozoans
Structure:
unicellular eukaryotes without a cell wall
Features:
Intracellular and extracellular parasites in order to obtain nutrients
Diseases:
malaria, giardiasis (“beaver fever“)
Fungi
Structure:
multicellular eukaryotes (yeasts are an exception) with a cell wall
.
Features:
Release digestive enzymes to perform extracellualar digestion ,thus, inducing inflammation (redness and swelling)
Diseases:
ringworm, “athlete’s foot”, yeast infection
Parasites
Structure:
multicellular eukaryotes without a cell wall (=animals)
Features:
Reside in host from which they take nourishment
Diseases:
Ex. roundworm and tapeworm infections (helminthosis)
RADaR System
protective system of immune system
- Recognize
- Attack
- Destroy &
- Remember
Cytokine
- small soluble proteins released from 1 cell & bind specific receptor of target cell in order to:
- regulate & facilitate immune system
- serve as weapons destroying cells
- influence non-immune cells
(ex: nervous system) Interleukins (IL), Interferons (IFN), Colony-stimulating factors (CSF)
1st line of defense
(Non specific external)
Barriers:skin & mucosa
Skin
a) Physical barrier
b) Releases antomicrobial substances: IgA, lysozyme (enzyme damaging bacterial walls)
, sebum,lactic acid, etc.
c) Hosts norma floura (nonpathogenic microorganisms
Mucosal membrane
(membranes lining openings):
a) Produce mucin (when hydrated, forms mucus)
b) Releases antimicrobial substances: (ex. IgA, lysozyme, lactic acid, HCl)
c) Hosts normal flora (nonpathogenic microorganisms)
2nd line of defense
(Non specific internal)
2a: cells (phagocytes, NK, eosinophils)
2b: chemicals (interferon, complement)
2c: physiologic (inflammation and fever)
If a pathogen enters our body, how does our body distinguish an invader from body’s own cells?
All cells have membrane surface molecules: carbohydrates (part of glycolipids and glycoproteins) and proteins. Many of these molecules are used for cell communication and help to distinguish your cells from invaders.
Major histocompatibility complex (MH1 class 1)
responsible for displaying fragments of the
normal cellular proteins as “badges” that identify each cell as belonging to the body.
However, if the cell is infected by a pathogen, it will be displaying foreign
fragments that will act as a “red flag” …
=> the infected cell will be
attacked
Sometimes, an abnormal cell (like, one that transformed into the cancer cell) will stop producing MHC class 1 molecules in order to “sneak” past the immune cells =>
the cancer cell will not be able to confirm its identity and will be attacked
2nd line:cells
A variety of immune cells can identify invaders and destroy them using various methods:
A. Destruction by eating
B. Destruction by launching “chemical weapons”
Destruction by eating
During an invasion, chemical signals attract
phagocytes (ex.neutrophils), which bind to the pathogen with the help of receptors, engulf & digest it
.
Destruction by launching “chemical weapons”
Natural killer cells (NK cells)-circulate in blood and destroy a wide variety of unhealthy body
cells (infected by viruses, tumor cells) by:
-forming a pore in a cell by releasing Perforin
-initiating apoptosis(programmed death) by
release of enzymes into the pore
Eosinophils- destroy parasites by releasing enzymes and other substances (ex. neurotoxins)
2nd line of defense: Chemicals
A.Interferons (IFN)
B.Complement System
Interferons (IFN)
class of cytokines released by a virus-infected cell to prevent viral spread:
Bind to the receptors of the neighboring non-infected cells to prevent them from becoming infected (initiates production of
enzymes that slow down protein synthesis and enzymes that will break viral RNA if viral invasion happens)
-Bind to the receptors of the neighboring infected cells
and trigger their apoptosis
Stimulate macrophages and NK cells
to_______________virus-infected cells
Complement System
30 proteins synthesized by liver and continuously released in inactive form in blood. Several mechanisms can be employed upon arrival of a pathogen (usually, bacteria)
Binding of a complement protein \_\_\_\_\_\_\_\_\_\_\_\_ to the pathogen will make it more likely to be phag ocytized . This process of “marking” a pathogen for destruction is called “opsonization”. K illing a pathogen by forming a \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_in its plasma membrane - membrane attack complex (MAC). \_\_\_\_\_\_\_\_\_\_\_\_ and \_\_\_\_\_\_\_\_\_\_\_ \_\_ of v arious immune cells, triggering inflammation
