Common Terms

There is a plethora of terms and short forms in immunity. Therefore we will cover the most common ones.

Antibody (Ab): also known as immunoglobulin (Ig). These are protein structures that come in a general “Y” shaped form that often couple together to form other types of immunoglobulins. (i.e. IgA, IgD, IgG, IgE and IgM)

Antigen: a short term for antibody generator. This means that it can be any object that leads to an immune response or the generation of antibodies by the immune system.

Antigen presenting cells (APCs): are cells that present antigen to other immune cells that can then incorporate the antigen in its recognition. The most common antigen presenting cells are: dendritic cells, macrophages and B-cells.

Bursa of Fabricius: where the well known B-lymphocytes are originated from. I will go into more detail about these cells in the future.

Cluster of Differentiation (CD): these are important cell surface proteins that act as ligands, receptors, stimulatory molecules and have many other functions. They are important in the signalling of the immune system.

Complement: an innate response that is composed of three different types of responses. The complement system recognizes common and conserved markers on pathogens that home in other cells to eliminate them.

-cyte: this is the Greek term for a cell. It is almost always accompanied by a prefix that descries the type of cell.

Cytokines: this word is Greek for “cell” and “movement”. They are actually proteins whose function is to take part in cell signalling. Often a cell releases cytokines that go and bind to other cells that initiates a type of response.

Granulocytes: cells that contain granules that are often used to degrade intercellular material.

Inflammation: the swelling of tissue. An inflammatory response occurs when the immune system recognizes pathogens and a variety of cells and cytokines cause the local blood vessels to enlarge as well as swell up the local tissue.

Interleukin (IL-): interleukins are an important class of cytokines that have many cell signalling functions. They are always accompanied by a number suffix. (i.e. IL-1β, IL-13)

Ligand: anything that binds to a certain receptor. Ligands may be molecules or proteins. Often proteins and CD’s have –L suffixes to indicate if it is a ligand.

Major Histocompatibility Complex (MHC): there are two types of MHC: I and II. This is present on almost all cells (red blood cells do not) and allows the immune system to recognize self versus foreign.  Antigens are also presented by antigen presenting cells on MHC.

Phagocytosis: when a cell engulfs another cell or extracellular material. Often called cell-eating.

Receptor: any protein that acts as a receptor to a specific ligand. They often initiate responses once its ligand is bound. Often proteins, cytokines and CDs have –R suffixes to indicate if it is a receptor.

T-lymphocytes: commonly known as T-cells. These cells originate from the bone marrow and then mature in the thymus. They are important cells in the immune system and I will describe their functions more in the future.