Cell recognition and the immune system Flashcards
what are our deffence mechanisms against pathogens? 3
- physical and chemical defences
- skin
- mucus
- tears - inflamationn
3.recognising foreign cells and targeting any pathogenic cells - specific immune response
which specific molecules are used to identify a cell.
protiens often part of the phospholipid bilayer - glycoprotiens.
what can the body recognise? 3
pathogenic cells
abnormal body cells
toxins
how is the specific immune response activated?
surface molecules used by the body to identify cells are antigens.
white blood cells known as phagocytes have surface protiens which act as receptors.
these bind to the antigens.
antigens found on a pathogen are presented on the surface of the phagocyte (now antigen presenting cell.)
this is used to recruit other cells of the immune system
specific immune response has been activated.
what is an antigen.
a molecule that triggers an immune response by lymphocytes.
roll of antigens
allow cell-cell recognition.
self and non self antigens
self antigens are made by the organism’s own body cells.
non- antigens stimulate an immune response.
antigen variability
if a pathogen exibits antigen variability,
the antigens present on their surface change frequently due to genetic mutations
this is an issue because receptors on lymphocytes and memory cells are complementary in shape to only one antigen.
lymphocytes and memory cells can no longer bind when antigens on the pathogen change.
the host gets infected and suffers the disease again.
what are the two types of phagocytes?
neutorphils
macrophages.
neutrophils
released in large numbers
short lived
chemicles released by pathogens aswell as chemicals released by the body cells under attack attract neutrophils.
this is called chemotaxis
neutrophils move towards the phagocyte which may be covered in antibodies.
antiboddies are a trigger for an attack.
the antibody receptors on the surface RECOGNISE AND ATACC.
what does a neutrophil attack look like
it attaches to the antibodies on the surface of the pathogen.
the cell surface membrane of the neutrophil extends out and around the pathogen, engulfing it and trapping it in a phagocytic vacuole
this is endocytosis.
this forms a phagosome (phagocytic vacuole)
lysosomes fuse with this phagosome to form a phagolysosome.
releases lysozymes to digest the pathogen.
NEUTROPHIL DIES AFTER DIGESTING THE PATHOGEN, PUS IS A SIGN OF DEAD NEUTROPHILS.
what is endocytosis
neutrophil:
recognise and attach to an antibody on a pathogen
extend cell surface membrane out and around the pathogen
engulf the pathogen and trap it in a phagocytic vacuole.
NEUTROPHIL DIES AFTER DIGESTING THE PATHOGEN, PUS IS A SIGN OF DEAD NEUTROPHILS.
what is the role of lysosomes in the non-specific immune system response?
digestive enzymes which DESTROY the pathogen.
NEUTROPHIL DIES AFTER DIGESTING THE PATHOGEN, PUS IS A SIGN OF DEAD NEUTROPHILS.
stages of neutrophils
- attraction (chemotaxis)
- recognition and attachment
- endocytosis
- bacteria within phagocytic vacuole
- fusion of lysosomes and phagocytic vacuole
- killing and digestion.
macrophages
larger in size
longer lived
move into organs (not exclusively blood)
do not destroy pathogens completely.
how do macrophages trigger the specific immune response.
do not destroy pathogens completely.
cut the pathogen up so they can display the antigens
lymphocytes characteristics
smaller than phagocytes
large nucleus fills most of the cell.
produced in bone marrow.
2 types - T and B
T lymphocytes and the cellular immune response.
mature in the thymus
have receptors
similar structure to antibodies and are specific to one antigen.
immature T cells divide by mitosis in bone marrow
production of T cell receptors occur sin thymus to mature the cell.
mature T cells each have a different receptor
this can be activated when it finds it’s specific antigen.
an activated T cell divides by mitosis to increase numbers.
what are the two types of T cell
helper T cells
cytotoxic T cells.
Helper T cells
secretes cytokines that stimulate B cells to divide and form plasma cells and memory cells.
Cytotoxic T cells.
Vacuoles in killer T cells contain toxins
Killer T cells punch holes in the cell surface membrane of infected body cells.
triggers apoptosis
the humoral immune response
B lymphocytes
mature in the bone marrow
each type of B lymphocyte cell can make one type of antibody molecule.
part of each antibody molecule forms a GLYCOPROTIEN receptor that can combine with one type of antigen.
if it finds that antigen, it can recognise it and bind to it, - clonal selection
it then divides by mitosis (clonal expansion.)
and it can differentiate into 2 main types of cell
plasma
memory.
