Lecture 4: Immune System Flashcards
main goals of the immune system
fight pathogens (such as bacteria and viruses) and inflammation, detect mutated cells, repair damaged tissue, and clean up dead and damaged cells
non-specific immune response
the body has the same reaction to different pathogens, and does not change over time
specific (adaptive) immune response
the body produces a specific response to eliminate a unique pathogen
- this response becomes progressively stronger
- the immune system can react quickly when a virus enters the body for the second time
white blood cells
protect the body from infection
- many of these cells are called luekocytes
- patrol the body, looking for signs of infection or abnormalities, such as mutated cells
platelets
play an important role in blood clotting
- all cells originate in the bone marrow, from a primordial cell that can differentiate
red blood cells
responsible for carrying oxygen from the lungs to the rest of the body and bringing carbon dioxide back to the lungs for exhalation
- unlike white blood cells and platelets, red blood cells do not play a direct role in the immune system
- called erythrocytes
infectious diseases
- bacteria: salmonella, chlamydia, etc.
- viruses: HIV, covid
- protozoa (very small worms): malaria, giardia
- fungi: candidiasis, trichophyton
what you can get sick from
- infectious diseases
- allergic reactions
- autoimmune diseases
non-communicable diseases
cancer, diabetes, cardiovascular disease, and COPD (asthma, bronchitis)
virus
consists of hereditary material in a casing (coat) that is able to reproduce by using the reproductive apparatus of living organisms (hosts)
- needs a cell from another organism in order to replicate itself
- binds to the cell and the information from the virus enters the cell making copies of DNA and RNA
- proteins are produced that allow new viruses to emerge and spread
defense against viruses
the skin, mucous membranes and acidity, and parts of the innate immune system can keep viruses and bacteria from taking over the body
infections
a virus must ‘take over’ a cell in order to replicate (cause an infection)
how infected cells die
- lysis (burst)
- apoptosis (programmed cell death or ‘suicide cell’)
viral infection
a specific type of infection caused by a virus
- the virus enters the body, invades host cells, and uses them to replicate and cause disease
- often require specific treatments
virus replication cycle
- adhesion
- penetration
- non-coating
- replication
- assembly
- release
adhesion
the virus attaches to the surface of a host cell by binding to specific receptors on the cell membrane
penetration
after attachment, the virus enters the host cell through endocytosis or membrane fusion
non-coating
the viral capsid breaks down, releasing the viral genome (DNA or RNA) into the host cell
replication
- DNA viruses use host cell proteins and enzymes to create additional DNA used to copy the genome or is transcribed into mRNA
- RNA viruses typically use the RNA core as a prototype for the synthesis of viral genomic RNA and mRNA
assembly
new viral particles are assembled by packaging the replicated genome and proteins into new capsids and create new virions
release
the new virions are released into the host system, where they can infect adjacent cells and repeat the replication cycle
- some are released when the host cell dies and other infected cells are left behind by crossing the membrane without directly killing the cell
vaccines
can be formed by using attenuated live viruses, killed viruses, or molecular subunits of the virus
live vaccines
usually made by weakening the ‘wild-type’ (disease-causing) virus by growing it in the laboratory in tissues or at temperatures different from what the virus is used to in the host
- allow the immune response to develop in time to prevent serious disease
- low but significant risk of these viruses returning to their pathogenic form through back mutations
antiviral drugs
often have a limited ability to cure viral diseases, but are used to control and reduce symptoms for a wide variety of viral diseases
- inhibit the virus by blocking the function of some of its proteins
vertebrate immune system
a complex system of defence against external and internal threats to the integrity of the body
- divided into the innate immune system and the adaptive immune system
innate immune system
not specific to a particular type of pathogen
- not caused by infection or vaccination and depends primarily on physical and chemical barriers that work on all pathogens
- first line of defence
adaptive immune system
links a very specific response to substances and organisms that do not belong in the body
- lasts longer and has a memory system that allows it to react with greater intensity if the body encounters a pathogen again, even years later
the skin
contains the protein keratin which prevents physical access to cells
- the surface of the skin is acidic preventing bacterial growth
mucous membranes
sticky mucus provides a physical trap for pathogens, preventing them from entering deeper into the body
hair
hairs protect the openings of the body, such as the nose and ears, from pathogens
saliva and tears
contain an enzyme that breaks down bacterial cell walls
gastric secretions
create a highly acidic environment that kills many pathogens that enter the digestive system
internal defence mechanisms
inflammatory response, phagocytosis, natural killer cells, and the complement system
monocyte
a type of white blood cell that circultes the bloodstream and lymph and develops into a macrophage after entering infected tissue