Effector cells are lymphocytes which can participate in the destruction of pathogens without having to go through further differentiation. This distinguishes them from naïve lymphocytes, which must first divide and differentiate before they can exercise effector functions, and from memory cells which must also differentiate and often also divide in order to develop into effector cells.

Electrophoresis is the movement of molecules in an electric field. Various forms of electrophoresis are used in immunology to separate mixtures of molecules - especially protein mixtures - and to determine the charge, size and sub-unit composition of individual molecules.

ELISA test: An ELISA test (enzyme-Iinked immunosorbent assay) is a serological test in which bound antigens or antibodies are detected with the help of a coupled enzyme which converts a colourless substance into a coloured product. It is often used in biological, medical and immunological research and diagnostics.

Embryonic stem cells can differentiate into all cell types of the body.

Enzymes: Organic substances which are involved in important chemical metabolic reactions of living organisms.

Eosinophile cells are polymorphonuclear leukocytes with eosinophile granuloma. They possess surface receptors for IgE which presumably enables them to attack parasites. They are activated by lymphocytes of the acquired immune response.

Epitope: An epitope is a site on an antigen which is recognized by an antibody. A T cell epitope is a short peptide from a protein antigen. It binds to an MHC molecule is and is recognized by a particular T cell.

Epstein-Barr virus: The Epstein-Barr virus (EBV) is one of the herpes viruses. It selectively infects human B cells. The virus causes a type of infectious mononucleosis (Pfeiffer's glandular fever) and results in a life-long infection of the B cells which is kept under control by T cells.