anaphylaxis
An antigen-specific immune reaction mediated primarily by IgE which results in vasodilation and constriction of smooth muscles including those of the bronchus and which may result in death of the animal.

androgen
A hormone that promotes the development and maintenance of male sex characteristics.

antibody
A molecule, produced by animals in response to antigen, that has the particular property of combining specifically with the antigen that induced its formation.

antigen
Any molecule capable of being recognized by an antibody or T-cell receptor.

APC (Antigen-Presenting Cell)
A term most commonly used when referring to cells that present processed antigenic peptide and MHC class II molecules to the T-cell receptor on CD4+ T-cells, e.g. macrophages, dendritic cells, B-cells. Note, however, that most types of cell are able to present antigenic peptides with MHC class I to CD8+ T-cells, e.g. as occurs with virally infected cells.

arthritis
Inflammation of a joint.

antitoxin
An antibody that can neutralize a specific toxin.

apoptosis
A form of programmed cell death, characterized by endonuclease digestion of DNA

autoantibody
An antibody acting against tissues of the organism that produces it.

autoimmunity
Immune recognition and reaction against the individual's own tissue.

autologous
From the same individual

azathioprine
An immunosuppresive drug used to prevent rejection of transplanted organs.

azurophilic
Has affinity for azure(blue) dye.