Biol.
1. Also called B lymphocyte . a type of lymphocyte, developed in bone marrow, that circulates in the blood and lymph and, upon encountering a particular foreign antigen, differentiates into a clone of plasma cells that secrete a specific antibody and a clone of memory cells that make the antibody on subsequent encounters.
2. Also called beta cell . a cell in the islet of Langerhans that produces and secretes insulin.
[ 1970-75; (def. 1) perh. B ( one-derived ); (def. 2) B ( ursa of Langerhans-derived ) ]