leukocyte
A white blood cell; functions to destroy foreign substances.

ligand
General term for a molecule recognized by a binding structure such as a receptor.

lymph
The tissue fluid which drains into and through the lymphatic system.

lymphocyte
A type of non-granular leukocyte(white blood cell) that mainly stays in lymphatic tissue (e.g., the lymph nodes) and is active in immune responses, including the production of antibodies.

lymphokine
A cytokine secreted by helper T cells in response to stimulation by antigens and that play a role in cell-mediated immunity.

lysosome
Membrane-bound vesicles, found in most cells especially phagocytic cells, usually containing hydrolytic enzymes.

lysozyme
An enzyme found in saliva and sweat and tears that destroys the cell walls of certain bacteria