second line of defence Flashcards
leukocyte
white blood cells, protect the body from pathogens
lymphocyte
a type of leukocyte but specific to the lymphatic system, B and T lymphocytes
phagocytes
cells that consume and destroy foreign or dead material through phagocytosis and digest them using lysosomes (macrophages, dendritic cells and neutrophils)
macrophages
a phagocyte found at sites of infection that perform antigen presentation (circle shaped)
dendritic cells
a phagocyte that performs antigen presentation (star shaped), found near the body’s surfaces
steps in phagocytosis and antigen presentation
- phagocytosis of pathogen
- fusion with lysosomes
- enzymes start to degrade pathogen
- pathogen broken in small fragments
- fragments of antigen presented on the cell’s surface
neutrophills
-a type of phagocyte that contains granules
-circulates the bloodstream
-most abundant
-Engulfs microbes and kills them with toxic chemicals
-First cells to arrive at an infection site in response to
chemical signals from other cells
-release cytokines
mast cells
-found between connective tissues, near external environments where pathogens can enter
-alert the rest of the immune system
-degranulate and release histamines when they detect injury or are stimulated by antigens/allergens
-cause the inflammatory response
eosinophils
-large granulated cells containing various toxic chemical mediators such as DNases. RNases, and proteases -help destroy pathogens
-found in tissues
-target pathogens too large to be phacytosed
-degranulate
natural killer cells
-circulate in the bloodstream
-recognise and cause destruction of damaged host cells through two receptors - killer inhibitory receptor, killer activation receptor
killer inhibitory receptor
examines the surface of cells for MHC 1 markers. If it succesfully binds to a sufficient number, the cell survives
killer activation receptor
bind to certain molecules undergoing cellular stress (like infected/cancerous cells)
