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physical barriers in animals
skin : Blocks pathogen entry
mucous membranes : Trap pathogens in nose, lungs, gut, etc.
chemical barriers in animals
Stomach acid: Kills ingested pathogens
Lysozyme (in tears/saliva) : Breaks down bacterial cell walls
microbiological barriers in animals
Normal flora (gut/skin bacteria) : Compete with pathogens for space & food
physical barriers in plants
Waxy cuticle : Prevents water loss + blocks pathogen entry
Cell walls : Tough structure to block pathogens
chemical barriers in plants
oxalic acid : distasteful to insects
Enzymes : (e.g. chitinase) Break down fungal cell walls
microbiological on plants
symbiotic bacteria - secrete toxins or outcompete w patho bacteria
what are allergens
trigger allergic reaction
non pathogenic
how is an immune system initiated
immune cells recognize a pathogen, present its antigens, and activate T helper cells to start the immune response.
Why is the adaptive response specific?
targets one specific antigen with memory.
What is natural active immunity?
come from an infection, immune system makes memory cells
What is artificial active immunity?
vaccine is injected – body makes memory cells.
how does vaccine make antibodies
safely exposes to dead/weakened version of pathogen
b cells are activated and make antibodies
some b cells become memory to rmb it
if real pathogen is exposed ltr on, body rmbs and knows how to fight
what is vaccine
substance that protects you from disease
contains a weakened/dead version of pathogen.
What is natural passive immunity?
occurs naturally, mother to baby (e.g. thru placenta or breast milk)
What is artificial passive immunity?
Injected antibodies – fast but temporary protection. (e.g. anti-venom injection)
humoral immunity
work in extracellular environments
b cells cant enter cells as they are only found in body fluid/blood and destroy pathogens from the outside.
cell mediated immunity
works in intracellular environments
some pathogens can hide among self cells
^ antibodies cant reach these pathogens bc antibodies found in blood/body fluid
cytotoxic T cells vs natural killer cells
Tc cells and Nk cells both release perforin and granzymes (perforin = makes pores in cell mb, granzyme = enters through pores, releases enzymes that trigger apoptosis)
Tc cells are part of the adaptive immune system, destory cells that present foreign antigen on mhc 1 (SPECIFIC)
Nk cells are part of innate, destory cells that don’t have mhc 1 on the (NON SPECIFIC)
humoral immunity steps
Pathogen enters the body and is broken down into antigen fragments
Antigen is displayed on the mhc 2 marker present on an apc
Helper t cell binds to the antigen present on mhc 2 marker and becomes activated (releases cytokines)
T helper cell helps B cell with the same b cell receptors will bind to the antigen
Naive b cell undergoes clonal selection and clonal expansion
Memory b cells and plasma b cells are produced
Antibodies will bind to pathogen and will cause functions of neutralisation, opsonisation, agglutination, complement activation, precipitation or etc
cell mediated immunity pathway
Pathogen enters the body, breaks down into antigen fragments
antigen is presented on MHC 1 marker
cytotoxic t cell with matching receptor binds to antigen present on mhc 1, becomes activated. gets help from helper t cells releasing cytokines asw
activated cytotoxic t cells will expand to make more Tc cells or memory t cells
cytotoxic t cells leave lymph nodes, bind to infected body cell. WILL RELEASE PERFORIN AND GRANZYME TO DESTROY CELL
memory t cells retain info for future infectiosn
steps of an allergic reaction
Allergen enters the body (e.g. pollen, peanuts).
Immune system overreacts and makes IgE antibodies.
IgE antibodies attach to mast cells.
On second exposure, allergen sticks to the IgE on mast cells.
Mast cells release histamine.
Histamine causes symptoms like sneezing, swelling, runny nose, itching.
autoimmune disease
immune system detects healthy cells as’nonself’ and triggers immune system to destroy and attac them in host tissue
why are booster vaccines good
ensures good amount of memory cells are made to fight off infection
when is histamine released
during inflammatory response
released from mast cells
cause vasodilation and increased vascular permeability (how easily small molecules can pass through blood vessel walls)
what is released during inflammatory response
histamine from basophils and mast cells
cytokines released by phagocytes (e.g. macrophages, neutrophils,etc)
MONOCLONAL ABS used to inhibit cytokine signals + reduce inflammation