THE IMMUNE SYSTEM
White Blood Cells
Phagocytes - Neutrophils
Produced throughout life by the bone marrow.
Scavengers – remove dead cells and microorganisms.
60% of WBCs
‘Patrol tissues’ as they squeeze out of the capillaries.
Large numbers are released during infections
Short lived – die after digesting bacteria
Dead neutrophils make up a large proportion of puss.
Larger than neutrophils.
Found in the organs, not the blood.
Made in bone marrow as monocytes, called macrophages once they reach organs.
Initiate immune responses as they display antigens from the pathogens to the lymphocytes.
If cells are under attack they release histamine.
Histamine plus chemicals from pathogens mean neutrophils are attracted to the site of attack.
Pathogens are attached to antibodies and neutrophils have antibody receptors.
Enodcytosis of neutrophil membrane phagocytic vacuole.
Lysosomes attach to phagocytic vacuole pathogen digested by proteases
B-cells mature in bone marrow then concentrate in lymph nodes and spleen
T-cells mature in thymus
B and T cells mature then circulate in the blood and lymph
Circulation ensures they come into contact with pathogens and each other
There are c.10 million different B-lymphocytes, each of which make a different antibody.
The huge variety is caused by genes coding for abs changing slightly during development.
There are a small group of clones of each type of B-lymphocyte