Antigens, Antibodies, and Basic Immune Responses - Anatomy and Physiology
- Which antibody class crosses the placenta?
- IgG, which gives the newborn passive immunity for its first months.
- Which cells secrete antibodies?
- Plasma cells, which are differentiated B lymphocytes.
- What is opsonization?
- Coating a pathogen with antibody or complement proteins so phagocytes recognize and engulf it more readily.
- Which antibody class is produced first in a primary immune response?
- IgM, a pentamer that is very effective at agglutination and complement activation.
- What is a hapten?
- A small molecule that is antigenic but triggers an immune response only when bound to a larger carrier protein.
- What is the basic structure of an antibody (immunoglobulin) monomer?
- A Y-shaped molecule of two identical heavy chains and two identical light chains joined by disulfide bonds.
- Which antibody class is the most abundant in serum?
- IgG, about 75 to 80 percent of circulating antibody, and the main class of a secondary response.
- Which antibody class binds mast cells and basophils to trigger allergic reactions?
- IgE. Antigen cross-linking IgE on mast cells releases histamine; IgE also helps defend against parasites.
- Which antibody class predominates in mucosal secretions, tears, saliva, and breast milk?
- IgA, which is secreted mainly as a dimer and protects mucosal surfaces.
- On which MHC class do helper T cells recognize antigen, and on which do cytotoxic T cells recognize it?
- Helper (CD4) T cells recognize antigen on MHC class II; cytotoxic (CD8) T cells recognize antigen on MHC class I.
- Which part of an antibody binds the antigen?
- The variable regions of the heavy and light chains at the tips of the two arms (Fab regions).
- What is an epitope?
- The specific part of an antigen that an antibody or lymphocyte receptor binds. One antigen can carry many epitopes.