Immunity Cells

B Cell

Type of response: Specific

Comes from: Bone Marrow

Role in Immune Response: Engulfs antigens to become an antigen presenting cell (APC). Once activated by a T-Helper cell, it divides and produces clones that become B-Memory cells and antibody-producing cells (plasma cells). 

B Memory Cell

Type of Response: Specific

Comes from: Clonally produced from activated B Cell.

Role in Immune Response: Not used in primary infection but can rapidly react in the secondary response to a particular antigen.

B Effector Cell

Type of Response: Specific

Comes from: Clonally produced from activated B Cell.

Role in Immune Response: Differentiates into plasma cell that produces a particular antibody. Each type of B Effector cell only makes plasma cells that produce one type of antibody.

T Helper Cell

Type of Response: Specific

Comes from: Produced in bone marrow and matures in the thymus.

Role in Immune Response: When it encounters an APC with complementary receptors, it binds to it and becomes activated, stimulating it to divide into clones that become T Memory Cells or active T Helper Cells. Active T Helper Cells produce cytokines that stimulate B Cells, natural killer cells and T Killer Cell division.

Memory T Helper Cell

Type of Response: Specific

Comes from: Clonally produced from an activaed T Helper Cell.

Role in Immune Response: No role in primary response to infection but is activated when the same antigen is encountered again, allowing a more rapid response.

T Killer Cell

Type of Response: Specific

Comes from: Produced in bone marrow and matures in the thymus.

Role in Immune Response: When it encounters an APC with complementary receptors, it binds to it and becomes activated. This stimulates it to divide to produce clones that become T Killer Memory Cells or active T Killer Cells. The T Killer Memory Cells have no role in primary response to infection but are activated when the same antigen is encountered again, allowing a rapid response. Active T Killer Cells bind to body cells that have been infected and secrete a chemical that makes pores form in the cell membrane of the infected cells. This causes the infected cells to swell up an burst.

Macrophage

Type of Response: Non-specific and Specific

Comes from: Develops from monocytes when they leave the blood and move into body tissues.

Role in Immune Response: There are large phagocytes that engulf bacteria, non-self particles and debris from damaged cells. They then digest these using enzymes from their lysosomes. They can engulf up to 100 bacteria before they die. In the specific immune response, they become APCs and activate T Helper Cells.

Neutrophil

Type of Response: Non-Specific

Comes from: Bone marrow.

Role in Immune Response: These are smaller phagocytes that can move in and out of capillaries and are usually the first to arrive at a wound. They engulf bacteria, foreign particles and debris and digest them with enzymes from their lysosome. They can only engulf between 5 and 20 bacteria before they die.

Natural Killer Cell

Type of Response: Non-Specific

Comes from: Bone marrow.

Role in Immune Response: These are non-specific lymphocytes. They are activated in several ways e.g. cytokines and interferon. They target cells missing 'self' markers and secrete chemicals that induce apoptosis.

Plasma Cell

Type of Response: Specific

Comes from: Activated B Effector Cell.

Role in Immune Response: Produces large numbers of antibodies specific to a particular antigen. Each clone of plasma cells only produces one type of antibody. Antibodies bind to antigens and make them stick together, making it easier for macrophages to recognise and engulf the antigens.

Antigen Presenting Cell (APC)

Type of Response: Specific

Comes from: APCs are either B Cells or macrophages that have engulfed bacteria or other antigens or are infected body cells. In each case, foreign antigens are displayed on the cell surface.

Role in Immune Response: T Helper and T Killer cells can only be activated by antigens that are displayed on the cell surface of an APC. T Helper cells can only activate B cells when they are antigen presenting.