glossary
ANAPHYLATOXIN
Inflammatory factors that are produced by the activity of the complement system - a part of the immune response.
ANTIBODY
Also known as Immunoglobulin. These are proteins which are produced by the plasma cells and released into the circulation. These antibodies bind to antigens and hold on to them, and by doing so allow other cells of the immune system to attack the antigens.
ANTIGEN
'Non-self' (or 'foreign') particles which, when introduced into the body, cause the immune system to react against them. An example of an antigen is a bacterium, and another is a virus.
B-CELL LYMPHOCYTE
B-cell lymphocytes form one arm of the lymphocyte branch of the immune system. They are part of the acquired/specific immune system.
BASOPHIL
One type of white blood cell belonging to the granulocyte family. Under certain conditions they release chemicals which dilate blood vessels. Thus they are important in the process of inflammation, and they also have a role to play in some types of allergies.
CELL LYSIS
The destruction of a cell wall, for example of a bacterium, causing it to rupture and spill out its contents. This leads to the death of the cell.
CELL-MEDIATED IMMUNITY
This branch of the acquired/specific immune system is based on the T-lymphocytes. The cells themselves destroy invading micro-organisms, particularly viruses that have infected our cells.
CHEMOTAXIS
The movement of phagocytic and other cells towards an invading micro-organism, or to the site of tissue damage. It is one of the functions of the complement system.
COMPLEMENT
This is a series of enzymes which interact with one another in a cascading sequence. When the first enzyme is activated, it triggers off the next one, and so on. In addition, each reaction is amplified and enlarged. The end result is the destruction of invading micro-organisms.
CYTOTOXIC
The ability to damage, or destroy, damaged cells of the body and other cells such as invading micro-organisms.
ENZYME
Enzymes are proteins which act as catalysts - they cause biochemical processes (reactions) to occur in living tissues at a very quick rate.
EOSINOPHIL
One of the white blood cells which form part of the non-specific (innate) immune system. It has a phagocytic action, and is particularly important in protecting us from parasitic infections such as intestinal worms.
FUNGUS
Fungi (the plural of fungus) are organisms that are much larger than viruses and bacteria. They can take the form of many shapes. They are responsible for many diseases, including 'thrush' (candida).
HUMORAL IMMUNITY
The branch of the immune system which is concerned with antibodies/immunoglobulins and whose cells are called B-lymphocytes and plasma cells.
IMMUNOGEN
An antigen which stimulates the body to produce an immune response. Note - not all antigens are immunogens.
IMMUNOGLOBULIN
Also known as an antibody (see ANTIBODY).
INCUBATION PERIOD
The period between becoming infected and showing physical signs of being infected. The length of time of an incubation period can vary from disease to disease.
LYMPH NODES
Structures which are part of the lymph system. Lymph passes through the nodes and is filtered to remove infectious micro-organisms.
LYMPHOCYTES
One of the white blood cells of the immune system. These cells are concerned with acquired/specific immunity.
LYSOZYME
An enzyme which is present in tears, nasal secretions, other mucosal secretions, and sweat. It occurs in lysosomes in cells. It has a 'bleach-like' action on bacteria and other micro-organisms, and it destroys them.
MACROPHAGE
One of the white blood cells (related to monocytes) which migrate to the tissues. It is a phagocyte.
MEDIATOR CELL
A cell which is part of the immune system, but does not actually kill micro-organisms. Instead, it helps (or mediates) the killer cells to do their job. Basophils and platelets are examples of mediator cells.
MOLECULE
A chemical combination of several atoms which form a chemical substance. One of the simplest molecules is that of water (H2O) - in other words water is made up of 2 hydrogen atoms and 1 oxygen atom.
MONOCYTE
A large phagocytic white blood cell.
NEUTROPHIL
A phagocytic white blood cell. Neutrophils are the most numerous of the white blood cells in the blood.
OPSONIN
Opsonins are found in blood and in other body fluids. They bind to non-self particles and make them more susceptible to being phagocytosed.
PHAGOCYTE
A cell of the immune system which ingests and then destroys micro-organisms, dead cells, and other débris in the body.
PLASMA CELL
Most of the B-lymphocytes mature into plasma cells, which then produce immunoglobulins.
PRIMARY IMMUNE RESPONSE
The immune response that our body makes when it first comes into contact with a particular antigen.
PROTEIN
A basic building block for our bodies. Proteins are made up of combinations of different amino acids.
RECEPTOR
Little 'bumps and hollows' on the surfaces of cells and micro-organisms which can be recognized by other cells. The particular pattern of these receptors on any cell or micro-organism is unique to that type of cell or micro-organism.
SECONDARY IMMUNE RESPONSE
This occurs when the body has already been in contact with a particular antigen, and has developed a 'blueprint' of it. The secondary response is much quicker to occur and it is much more powerful than is the primary response.
THYMUS
An organ situated just behind and slightly below the sternum. This is where T-lymphocytes mature, differentiate into their different subsets, and learn to recognize 'self' cells from 'non-self' cells. It is relatively large in the very young, but it atrophies (shrinks) as we get older.
STEM CELL
An immature blood cell found in the bone marrow which will eventually develop into different cells such as lymphocytes, platelets, erythrocytes, etc.