The Cells of the Immune System
Aims and Objectives
By the end of the module you should be able to:
- appreciate the common origin of the cells of the immune system from the
bone marrow
- describe in simple terms the microscopic appearance of the cells of the
immune system:
- B and T lymphocytes
- plasma cells
- macrophages
- dendritic cells
- describe in simple terms other effector cells such as:
- neutrophil polymorphs
- eosinophil polymorphs
- mast cells
The major cell types in the immune system are lymphocytes and phagocytic/dendritic cells.
1. Lymphocytes
There are two broad sub-types of lymphocyte. These are known as B cells and T cells. All of them are derived from the bone marrow but T cells undergo a process of maturation in the thymus gland. Mature lymphocytes all have a similar appearance. They are small cells with a deeply basophilic nucleus and scanty cytoplasm. B and T cells circulate in the blood and through body tissues. B cells give rise to plasma cells which secrete immunoglobulins (antibodies). T cells also respond to antigens. Some of them (CD4+) secrete lymphokines which act on other cells involved in the immune response. Others (CD8+, cytotoxic) are able to cause lysis of infected cells.
2. Macrophages and dendritic cells
These cells are derived from the bone marrow and have a variety of functions in the immune response:
- phagocytosis
- secretion of cytokines
- antigen presentation
The cells performing these various functions have differing microscopic appearances but they are grouped together as the mononuclear phagocytic system.
Polymorphs and mast cells are also involved in the effector side of the immune response.
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Click on any of the cells below to identify the cell type and get further
information:
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