immunity definitions

• Pathogen Definition


  A microorganism that can potentially cause disease.
• Antigen Definition


  A molecule that triggers an immune response; usually large, e.g. protein, polysaccharide, glycoprotein.
• Antibody Definition


  A protein secreted by B lymphocytes; each one specific to a different non-self antigen .
• B lymphocyte Definition


  A white blood cell that causes a humoural response to infections by secreting antibodies; matures in the bone marrow.
• T lymphocyte Definition


  A white blood cell that causes a cellular response to infection; matures in the thymus.
• Humoral Response Definition


  Term given to describe the way in which B lymphocytes produce antibodies in response to infection.
• Cellular Response (mediated) Definition


  Term given to describe the way in which T lymphocytes respond to an antigen-presenting cell.
• Plasma cell definition


  Type of B lymphocyte which releases antibodies; formed when a B lymphocyte divides and produces clones.
• Memory cell Definition


  Type of B lymphocyte that remains dormant in blood and recognises antigens if they enter the blood again so that antibody-producing cells are produced faster than before.
• Antigen-Presenting Cell Definition


  A 'self' cell has been infected; now has the pathogen's antigens on its cell surface.
• Histamine Definition


  Chemicals released to help phagocytes squeeze through gaps in capillary walls.
• Lysosomes Definition


  Organelles present in large amounts inside phagocytes; contain enzymes to digest the pathogen.
• Phagocyte Definition


  Type of white blood cell that ingests and digests pathogens.
• Non-specific inflammatory response Definition.

  Term given to processes involving phagocytes