Lesson4 - Immune System Flashcards
what is the function of the immune system?
target and destroy the pathogens that invade the animal’s body
what are pathogens?
microbes and viruses that cause disease
what is the microbiota?
beneficial bacteria, non-pathogenic or commensal microbes
the immune system of animals can be split into 2 things, which are?
- innate immunity
- adaptive immunity
what is innate immunity?
A defense system that operates in all animals. ex: barrier defenses, cells specialized in the rapid recognition of pathogens, and chemical defenses
adaptive immunity is a defense system exclusive to…?
vertebrates
which cells are specialized cells of the adaptive immune system?
B cells and T cells called lymphocytes
what is the function of lymphocytes?
target specific pathogens by recognizing specific parts of specific molecules of specific pathogens
in insects, what is the innate immunity barrier?
chitin exoskeleton - a barrier defense that protects against intruding microorganisms
what happens once the first line of defense is breached in insects?
specialized cells circulating in the hemolymph seek and destroy invading pathogens
what are hemocytes?
-the phagocytic cells that recognize pathogens from molecules on their cell surface.
-once engulfed by a hemocyte, the pathogen is confined to a vacuole that fuses with a lysosome containing enzymes that destroy it.
-digested pathogen is exported out of the phagocytic cell via exocytosis.
what are the functions of hemocytes circulating in the hemolymph? (2)
- secrete short-chain amino acids called antimicrobial peptides
- recognize and engulf pathogens
what can antimicrobial peptides do?
can perforate the plasma membrane of pathogens and instantly cause them to lyse
what do bacteria lack? what does that have to do with pathogens?
- a cytoskeleton
- puncturing plama= contents of the cell spill out
where do lymphatic vessels equipped with one-way valves, that move fluid unidirectionally, move the fluid towards by bulk flow?
a vast network of lymph nodes
where does the interstitial fluid collected from the top right half of the body drains into?
the right subclavian vein
where does the interstitial fluid collected from the left and bottom half of the body drain into?
left subclavian vein
what are the primary tissues of the immune system?
bone marrow and the thymus, where the cells of the adaptive immune system develop and mature
what are the secondary tissues of the immune system?
- adenoid gland
- tonsils
- spleen
- peyer’s patch
- appendix
- large intestine
what does the barrier defense include in mammals?
1.skin
2. secretion from glands
3. mucous membranes of the digestive, respiratory, and urogenital tracts
what prevents the growth of pathogenic microbes?
- commensal bacteria
- skin
- lining of urogenital tracts
what in the respiratory tract moves pathogens tapped in the mocus uo towards the pharynx where they are swallowed?
the cilia of the pseudostratified columnar epithelial cells - prevents mucus from reaching the alveoli
what contributes to making surfaces protescted from pathogenic bacteria?
- acidic secretions from sebaceous glands in the dermis
- lacrimal glands above the eye
- salivary glands in the mouth
what happens to the pathogens that escape the innate defenses of the oral cavity?
they are destroyed by the highly acidic secretions from the gastric glands in the stomach.
what are TLRs?
Toll-like receptors
where do leukocytes (white blood cells) come from?
stem cells in the bone marrow.
White blood cells include neutrophils, monocytes, basophils, eosinophils, and lymphocytes.
which cells are the phagocytic cells of the innate immune system?
- neutrophils
monocytes: - macrophages
- dendritic cells
which cells do lymphocytes include?
B cells
T cells
natural killer cells (only one that is part of innate immunity)
function of killer cell?
seek and destroy virus-infected cells and cancer cells
where do neutrophils circulate?
in the blood and only against tissue upon infection
where do monocytes travel?
specific body tissues
ex: the dermis
and differentiate into macrophages
what is the inflammatory response?
- macrophage phagocytozes a pathogen
- macrophage secretes signalling molecules- cytokines
- cytokines causesmast cells to degranulate and release histamines
- histamines cause nearby blood capillaries to dilate
- allows neutrophils in blood to access infected tissue and phagocytizing.
which die first? macrophages or neutrophils?
neutrophils
where do we find macrophages? (3)
- dermis
- alveoli of the lungs
- lymph nodes
which cells are the link between innate immunity and adaptive immunity?
dendritic cells
are natural killer cells phagocytic?
no, they are non-phagocytic.
function o fnatural killer cells?
forage for abnormal cells. once virus or cancer detected, NK cells release molecules called perforin, then grandzymes spill into the pores and destroy abnormal cell from the inside.
which cells phagocytize the debris of NK cells?
macrophages and dendritic cells
what are the protein based chemical defenses of the innate immunity?
1.antimicrobial peptides (saliva)
2.interferons- produces anti-viral proteins that block the virus from replicating
3.complement system
where do B cells reside to mature?
bone marrow
where do T cells reside to mature?
thymus
what are the surface molecules on pathogens calles? what are the subtypes?
antigens - proteins, polyssaccharides
what is the binding site of the B cells and T cells on the antigen called?
the epitope - a small cluster of amino acids or sugar molecules
what is the function of B cells? vs T cells?
B cells = destroy pathogens circulating in body fluids- called humoral immunity
T cells = target pathogens hiding within body cells- called cell-mediated immunity
what is the form of a B cell?
has a Y shaped receptor and composed of 4 polypeptides- 2 light chains and 2 heavy chains
epitome ends of antigens bind to terminal ends of the variable regions
what is the form of T cells?
stick-like and composed of 2 polypeptides - an alpha chain and beta chain.
we have approx. 10 million T cells in the body, each with a different variable region
what is a key difference between B cells and T cells?
B cells bind to intact antigens vs. T cells bind to antigens anchored on the surface of host cells
what happens during clonal selection?
after engulfing a pathogen, macrophages and dendritic cells move antigens to the outer surface of their plasma membrane and affix them to a protein called major histocompatibility complex (MHC). All cells in the body EXCEPT red blood cells have MHC receptors on their plasma membrane. Macrophages, B cells, and dendritic cells, have a unique variety called class II MHC.
do all other cells except B cells, macrophages and dendritic cells have MHC II OR MHC I?
MCH I
Which 2 cells does the proliferation stage of B cells and T cells produce?
effector cells
memory cells
what are the effector cells of activated B cells?
plasma cells - they have an exaggerated endoplasmic reticulum that begins to secrete soluble antigen receptors called antibodies. secreted into fluids, antibodies bind to pathogens, such as viruses and bacteria, and toxins, flagging them for destruction
what is the increased rate of phagocytosis called?
opsonization
what are the effector cells of activated helper T cells?
cytotoxic T cells - destroys virus-infected body cells- recognizes antigens displayed on infected host cells- fixed to class I MHC molecules
