Antibodies Are Proteins

Antibodies are proteins released from plasma cells (differentiated B cells) in response to specific antigens. Their role is to bind to, and precipitate these antigens and render the pathogen inactive. This essay will describe how these anti-influenza antibodies are synthesised and perform this role.

Influenza is a virus that infects humans. It enters the lungs via ventilation system and breaches the gas exchange surface (the lungs) and enters the epithelial cells. Here it enters the nucleus and uses endonuclease enzymes to seal its DNA across that of the host. This alters the control and regulation of the cells. On replication of the DNA, the DNA of the virus is also replicated and through differential gene expression, this alters the antigens that are expressed on the surface of the cells, altering their shape. The damaged cells may release locally-acting chemical mediators such as prostaglandins or histamine to increase the permeability of the capillaries to white cells such as T lymphocytes to coordinate the immune response.

T lymphocytes are a class of white blood cell involved in cell-mediated immunity that targets antigens that are non-host. An antigen is any structure that identifies a structure as non-host and the T cells have receptors that have a complementary shape that can bind and recognise them. Upon binding to the antigens on the surface of the infected cell a T-memory cell will become activated and divide by mitosis to form clones which differentiate into more memory cells (to provide a longer term immunity and a faster secondary response), a T-killer cell that binds and destroys the infected cells causing the lysis of its cell membrane, and a T-helper cell which releases cytokines that activate B-cells.

The B cells are another class of lymphocyte involved in humoral immunity. Once activated, they divide by mitosis and differentiate into B-memory and plasma cells. The plasma cells have the capacity to produce a specific antibody that is a protein which can be released to cause the precipitation of the invading pathogen.

The antibody they release is a y-shaped globular protein with a constant region and a variable region that has a complementary shape to the target antigen, in this case a part of the influenza-causing virus. The T-helper cell had released cytokines which bound to specific receptors of the cell surface membrane of the B cell. This activation triggered a differential gene expression which caused specialisation into an antibody-secreting B-cell. A part of this specialisation