n :  a beta globulin of low molecular weight that is present at a low level in plasma, is normally excreted in the urine, is homologous in structure to part of an antibody, comprises the light chain in certain histocompatibility antigens, and occurs at elevated levels in blood serum or urine in some pathological conditions (as tubulointerstitial disease) .
 
 chiefly Brit   
 
Published under license with Merriam-Webster, Incorporated.  © 1997-2024.