L

LAL

Limulus Amebocyte Lysate

Leukocyte

See white blood cell. Gray's Anatomy

Lipid

Any of a group of organic compounds, including the fats, oils, waxes, sterols, and triglycerides, that are insoluble in water but soluble in nonpolar organic solvents, are oily to the touch, and together with carbohydrates and proteins constitute the principal structural material of living cells.

Lipopolysaccharide

Any of a group of polysaccharides in which a lipid constitutes a portion of the molecule.

Lipoprotein

Any of a group of conjugated proteins in which at least one of the components is a lipid. Lipoproteins, classified according to their densities and chemical qualities, are the principal means by which lipids are transported in the blood.

Lipoprotein(a)

A low density lipoprotein containing structures similar to the plasminogen molecule. Increased lipoprotein(a) has been identified as a major independent risk factor for coronary disease and stroke.

LMW

Low Molecular Weight

Low Molecular Weight Heparin (LMWH)

Heparin with a mean molecular weight of about 5,000 - commercially prepared by enzymatic depolymerization of conventional porcine heparin, LMWH does not prolong the APTT as much as high-molecular weight Heparin and binds less to platelets. A low molecular weight fraction of a heparin preparation that has more anti-Xa activity and more predictable dose response than standard, unfractionated heparin.

Low-density Lipoprotein (LDL)

A complex of lipids and proteins, with greater amounts of lipid than protein, that transports cholesterol in the blood. High levels are associated with an increased risk of atherosclerosis and coronary heart disease.

Lupus Anticoagulant

Antibodies against phospholipids which inhibit blood clotting in a test tube, but may be associated with a higher risk of clotting in people who have them in their blood.

Lymph

Clear, watery, sometimes faintly yellowish fluid derived from body tissues that contains white blood cells and circulates throughout the lymphatic system, returning to the venous bloodstream through the thoracic duct. Lymph acts to remove bacteria and certain proteins from the tissues, transport fat from the small intestine, and supply mature lymphocytes to the blood.

Lymphatic System

The interconnected system of spaces and vessels between body tissues and organs by which lymph circulates throughout the body. Gray's Anatomy

Lymphocyte

Any of the nearly colorless cells found in the blood, lymph, and lymphoid tissues, constituting approximately 25 percent of white blood cells and including B cells, which function in humoral immunity, and T cells, which function in cellular immunity. Bloodline

Lymphokine

Any of various substances released by T cells that have been activated by antigens. They function in the immune response through a variety of actions, including stimulating the production of nonsensitized lymphocytes and activating macrophages.

Lyophilize

To freeze-dry (blood plasma or other biological substances).

Lysis

The dissolution or destruction of cells, such as blood cells or bacteria, as by the action of a specific lysin that disrupts the cell membrane.