Antibody Russell Weller Mar 13, 2023 A blood protein, made by plasma cells (a type of white blood cell, part of the immune system), in response to and counteracting a specific antigen (object or substance). Related Articles: Glossary: Immunoglobulin IgDGlossary: Intravenous ImmunoglobulinGlossary: Intravenous Immunoglobulin (IVIG)