Immune System Flashcards
lymphatic system + immune response
comprises of several structures + organs:
lymphatic tissue, bone marrow, lymph, lymphatic vessels
protects us against disease
lymphoid cells respond to envirobmental pathogens, toxins, abnormal body cells incl cancers
pathogens that cause disease: viruses, fungi, parasites, bacteria
parts of lymphatic system
lymph- fluid- simialar to plasma without plasma proteins
lymphatic vessels- carry lymph from peripheral to venoys system
lymphoid tissues- inestinal nodes + lymphoid organs (thymus + spleen)
lymphoid cells- lymphocytes, phagocytes
function of lymphatic system
1- produce, maintain and distribute lymphocytes
production occurs in lymphoid tissues, lymphoid organs and red bone barrow
distribution- travels through lymphatic vessels and capillaries, detects problems, travels into site on injurt/ infection
- return fluid and solutes from peripheral tissues to blood
- distribution of hormones, nutrients and waste products from tissue of origin to circulation
lymphatic capillaries
+ lymph trunks and ducts
start as blind pockets rather than tubes
have larger diameter + thinner walls than blood capillaries
flat or irregular in cross section
lymph trunks and ducts:
lymph passes through lymph nodes and into lymph trunks (lumbar + intestinal trunks) from lymphatic vessels
lymph trunks merge to form either thoracic duct or right lymphatic duct
circulating lymphocytes
T cells- thymus dependent- thymus grows when you are born and begins to shrink when you reach 16- cell mediated immunity
B cells- bone marrow derived- antibody mediated immunity
NK cells- mtural killer cells - bone marrow derived (non specifc immune response)
lymphatic organs and tissues
primary lymph organs (where immune cells become immunocompetent) -red bone marrow + thymus
secondary lymphatic organs and tissues- lymph nodes, spleen, lymphoid nodules
structure of lymph node + flow through
germinal centres- where B cells produce anitbodies
route of lymph flow:
from subscapular spacw (contains macrophages and dendritic cells)
through outer cortex (contains B cells within germinal centres)
through deep cortex- dominated by T cells
through the core (contains B cells + plasma cells organised into medullary cords)
into hilium and efferent lymphatics
efferent lymph vessels- take lymph fluid out and away from lymph node
afferent lymph vessels- take lymph fluid towards/ into lymph node
lymphoid nodules
dont have fibrous capsule unlike lymph organs and lymph nodes
nodules are bundles of lymphoid tissue without fibrous capsule
in lumen of gut (intestinal lumen), in tonsins + appendix
flow of lymph
interstitial fluid > lymph capillaries > lymph vessels > lymph trunks > lymph ducts > subclavian veins
lymph nodes
purfiy lymph before returning to circulation
removes debris, pathogens + antigens
distribution
lymph nodes of gut trachea, lungs + thoracic duct protect against pathogens in digestive + respiratory systems
lymph nodes (glands) large lymph nodes at groin and base of neck, swell in response to inflammation
lymphadenopathy- chronic or excessive enlargement of lymph nodes may indicate infections, endocrine disorders or cancer
innate vs adaptive immune response
non specific (innate)- block/ attach to any potential pathogen, present from birth, no memory
eg NKC, macrophae, neutrophil
specific (adaptive)- identify, attach and develops immunity to a specific antigen, acquired in response to antigens
eg B cell, T cell
non specific defence
physical barriers - eyes, skin, respiratory + digestive tract
phagocytotic cells
immunological surveillance (NK cells)
interferons (antiviral) - secreted by NK cells
complememt system- complement proteins (cover/coat pathogen)
inflammation- increase blood flow, activate phagocytes etc
fever- body temp rise, mobilises defenses, inhibits pathogens
phagocytosis and antigen presentation
- pathogen phagocytised by APC
- lysosome action produces antigenic fragments
- endoplasmic reticulum produces class II MHC proteins
- antigenic fragments are bound to class II MHC proteins
- antigenic fragments are displayed by class II MHC proteins on cell membrane
MHC= major histocompatibility complex
classes of phagocytes
microphages- neutrophils + eosinophils (granulocytes), leave the blood stream + enter peripheral tissue to fight infections
macrophages- large phagocytic cells derived from monocytes distributed throughput the body, make up monocyte- macrophage system (reticuloendethelial system), may be fixed or free (within tissue/ in circulatory system)
activated macrophages- respond to pathogens in several ways
engulf pathogen and destroy it with lysosomal enzymes, bind to pathogen so other cells can destroy it, destrot pathogens by releasing toxic chemicals into interstitial fluid
immunological surveillance
- recognition and adhesion
- realignment of golgi apparatus
- secretion of perforin
- lysis of abnormal cell
lines golgi apparatus up with target cell (abnormal cell) , secretes perforin + enzymes (granzyme) enters through pore and breaks up components of cells
perforin- small molecules which bind together to form a pore- perforates cell
interferons
non-specific response to viral infections
interferons are proteins (cytokines) released by activated lymphocytes and macrophages
3 types
alpha- produced by leukocytes, stimulate NK cells
beta- secreted by fibrocytes, slow inflammation
gamma- secreted by T cells and NK cells, stimulate macrophage activity
complement system
enhances (complements) ability of antibodies and phagocytic cells to clear pathogens from an organism
effects of complement activation
attraction of phagocytes, enhancement of phagocytosis by opsonisation, stimulation of inflammation, destruction of target cell membrane (MAC)
complement cascade
bacteria coated with antibodies
compliment binds to antibodies
starts a cascade, allows compliment proteins to form membrane attack complex (similar to perforin)
creates pore on surface of bacteria, casuing it to lyse
conversion of C3 to C3b active form
inflammation and tissue repair
response to tissue damage
increased blood flow
mast cells release histamine
phagocytes (neutrophils) move to site
neutrophils remove debris
clot formation/ removal of debris
activation of fibrinogen= tissue repair
fever
increase in body temp due to release of pyrogens (any material that causes hypothalamus to raise body temp)
mobilises defences, accelerates repair, inhibits pathogens- growth + division
specific immunity
adaptive immunity against pathogens
acquired upon exposure to specific antigens
cell mediated and humoral (antibody)
cd8 cells- cytotoxic/ killer T cells
cd4- helper T cells - help B cells produce antibodies by activating
T cells become specific- some become memory and some die
some B cells become memory cells and others become plasma cells which produce antibodies
cell mediated- intracellular pathogens eg virus infected + antibody mediated= extracellular pathogens eg bacteria, antigen presenting cells
T cells
cell mediated immunity
T cells only recognise fragments of antigenic proteins that are processes and presented in a certain way
B cells
humoral/ antibody mediated
B cells can recognise and bind to antigens in lymph, intersitial fluid or blood plasma
MHC proteins
used to distinguish self and non self
class I on all nucleated cells (1 leg)
class II on APC + lymphocytes (2 legs)
