# 63 Summary of Immunity

1 Phagocytes and lymphocytes are the cells of the immune system.

2 The diagram shows how to recognise phagocytes and lymphocytes in microscope slides and photomicrographs of blood.

# 62 Immunity and vaccination

A person is immune to a disease if the pathogen that causes the disease is unable to reproduce in the body and cause illness. This happens when the body already contains, or is able rapidly to make, large quantities of antibodies against the antigens associated with the pathogen.

# 61 Action of T-lymphocytes

T-lymphocytes include T helper cells and T killer cells. Both of these types of cell place their specific receptors in their cell surface membranes. On encountering the relevant antigen, they are activated and divide by mitosis to form a clone.

# 60 Action of B-lymphocytes

A B-lymphocyte places some of its specific receptor molecules in its cell surface membrane. If it encounters an antigen that binds with this receptor, the B-lymphocyte is activated. It divides repeatedly by mitosis to produce a clone of genetically identical plasma cells.

#59 The immune response - Lymphocytes

Lymphocytes, unlike phagocytes, act against specific pathogens. Each lymphocyte contains a set of genes that codes for the production of a particular type of receptor. We have many million different types, each producing just one type of receptor.

# 58 The immune system - Phagocytes

Credit: Pass My Exams.

The human immune system is made up of the organs and tissues involved in destroying pathogens inside the body.
There are 2 main groups of cells involved:
• phagocytes: ingest and digest pathogens or infected cells;
• lymphocytes: 
- recognise specific pathogens through interaction with receptors in their cell surface membranes
- respond in one of several ways, for example by secreting antibodies.

#57.2 Immunity - Syllabus 2016 - 2018

11.1  The immune system
11.2  Antibodies and vaccination

#57 Immunity - Syllabus 2015

• The immune system
• Vaccination