immunity Flashcards
what does our immune system do?
protects you against disease by detecting ‘foreign’ antigens and distinguishing them from self antigens
uses innate and adaptive immune system to detect and destroy these antigens
leads to long lasting immunity against this particular antigen
what is an antigen
molecules (proteins) that are on the surface of cells that can generate immune response
what do antigens allow us to identify?
pathogens, abnormal cells, toxins and foreign cells
what is innate immunity?
a set of natural barriers to resist infection by pathogens
non- specific, they are the same for every pathogen
examples of innate immunity
skin acts as a barrier
inflammation
mucus
phagocytes
what is our first line of defence if pathogens enter the body and what do they do?
- phagocytes destroy pathogens by engulfing and destroying by the use of hydrolytic enzymes (lysozymes)
- can trigger adaptive immune system via process known as antigen presentation
first step of antigen presentation?
a phagocyte recognises the foreign antigens
what happens after foreign antigens are recognised?
cytoplasm and cell membrane of the phagocyte begins to move around the pathogen
what happens after cytoplasm and cell membrane begin to move around pathogen
two edges of membrane meet and fuse surrounding the pathogen ( which has been engufled)
what happens after membrane fuses around pathogen?
pathogen now contained in a phagocytic vacuole
what happens after pathogen in phagocytic vacuole?
lysosomes fuse with the vacuole
what happens after lysosomes fuse?
lysozymes released into phagocytic vacuole which breaks down the pathogen
what happens after pathogen breaks down?
phagocyte incorporates antigen molecules into their own cell membranes
final step of antigen presentation?
antigen molecules are presented by the phagocyte to other immune cells causing an immune response to be initiated
what is the adaptive immune system?
when pathogens bypass the innate immune system, the adaptive immune system is activated by antigen presenting cells
- produces a specific response to each different antigen it encounters
- provided by lymphocytes which come from bone marrow
what does the adaptive immune response cause us?
long lasting immunity to a particular pathogen but acts slower than the non-specific response
what is the cell-mediated response?
- activation of t-lymphocytes
- t cells are formed in bone marrow but mature in thymus
- activated by phagocytes presenting antigens to them
what is the first step of cell mediated response?
antigen presenting cell is detected by t-helper cell with the same complementary receptor, t cell is activated
what happens after the t-cell is activated?
the t-cell now undergoes clonal expansion where is divides to form more t-cells (with same complementary receptors) by mitosis
what happens after clonal expansion (t-cells)?
these cells differentiate into T-cytotoxic cells (killer), T- memory cells and T-helper cells
what happens after differentiation of T-cells?
T-helper cells release interleukins to activate the B-lymphocytes to start the humoural response
what are T-memory cells?
cells that remain dormant in the circulation, awaiting further encounters with the same antigens where they begin rapidly dividing to form more t-lymphocytes?
what are T-killer cells?
bind to and kill pathogenic cells by lysing them using perforins
what are T-helper cells?
release cytokines which stimulate antibody producing B-lymphocytes and phagocytes.
