WBC
granulocytes (neutrophils)
monocytes (macrophages)
lymphocytes ( T- lymphocytes) (B-lymphocytes)
phagocytes ( neutrophils & macrophages)
Phagocytes ( neutrophils & macrophages)
- made in bone marrow
- they’re scavengers - removing any dead cells and invasive organisms
Neutrophils
- have a lobed nucleus and granular cytoplasm
- short-lived cells
Macrophages
*larger than neutrophils
* travel in blood as monocytes which develop into macrophages once they leave blood and settle in organs, removing foreign matter there
* long-lived cells
* do not destroy pathogens completely, they’re cut up and their antigens are displayed, hence it becomes an antigen presenting cell (APC)
Phagocytosis
- during an infection (caused by pathogens invading the body), cells under attack respond by releasing chemicals called histamines
- these attract neutrophils
- this movement towards chemical stimulus is called chemotaxis
General steps of phagocytosis
1) attraction (chemotaxis)
2) recognition and attachment
3) endocytosis
4) bacteria trapped within a phagocytotic vacuole
5) fusion of lysosomes and phagocytotic vacuole
6) killing and digestion
Lymphocytes
B-lymphocytes ( B- plasma & B - memory)
T- lymphocytes ( T - helper, T- killer (cytotoxic) & T- memory)
B- Cells
- made and mature in the bone marrow
- travel to the spleen for final stages of maturation
1) B-plasma cells
* short-lived
* produce antibodies
2) B-memory cells
* form the immunological memory of the body
* responsible for 2° response
T-cells
Made in the bone marrow but mature in thymus.
T-helper
* produce interleukins
* interleukins stimulate:
1) B-cells to make antibodies
2) other T-cells to divide
3) macrophages to enhance the effect of
phagocytosis
T-killer (cytotoxic)
* destroys cells by releasing perforin which makes holes
in the cell surface membrane
T-memory
* leads to immunological memory of antigen
* responsible for 2° response
