White Blood Cells (SQA National 5 Biology): Revision Note

The body's immune system is highly complex

White blood cells are part of the immune system and are involved in destroying pathogens

• Pathogens include bacteria, viruses and fungi

Once a pathogen has entered the body, the role of the immune system is to prevent the infectious organism from reproducing and to destroy it

White blood cells make up less than 1% of total blood volume

There are two main types

• phagocytes

• lymphocytes

Phagocytes carry out phagocytosis

• They have a sensitive cell surface membrane that can detect chemicals produced by pathogens

• Once they encounter a pathogen, phagocytes will engulf it and release digestive enzymes to digest it

• This is a non-specific immune response

Lymphocytes are white blood cells that produce antibodies

Antibodies are proteins with a shape that is specific (complementary) to the antigens on the surface of the pathogen

• An antigen is a marker on the surface of a cell or pathogen that the body sees as foreign and causes the immune system to respond

Lymphocytes provide a specific immune response, as the antibodies produced will only fit one type of antigen