Chapter 34. The Immune System Flashcards
polypeptide segments in immunoglobulin L and H chains which display great sequence variability and which are responsible for antigenic specificity.
Complementarity-determining region (CDR)
One of two 50-kd polypeptide chains produced when immunoglobulin G (IgG) is cleaved by the protease papain; the Fc fragment of an intact IgG molecule cannot participate in antigen binding but can mediate other important biological activities, such as complement fixation.
Fc
One of two 50-kd polypeptide chains produced when immunoglobulin G is cleaved by the protease papain; Fab fragments bind antigens but cannot cross-link them, because each fragment has only one binding site for an antigen.
Fab
a system for recognition of foreign substances that employs soluble antibodies to bind to and inactivate such substances.
Humoral immune response
precursors to plasma cells, which are antibody-secreting cells.
B lymphocyte (B cell)
An evolutionarily ancient defense system that responds rapidly to features present in many pathogens. The innate immune systems includes the epithelial lining that surrounds host cell, phagocytes, and a family of receptors that can recognize specific features present in most pathogens.
Innate immune system
A foreign substance that elicits the synthesis of an antibody.
Antigen
a 50-kd polypeptide that is one of two types of paired chains found in the immunoglobulin G molecule; each heavy (H) chain consists of a variable region and three constant regions, and each chain is linked by a disulfide bond to a light chain.
Heavy (H) chain
A specific molecular characteristic found primarily on invading organisms that is a critical component of the pathogen's function. PAMPs are targets of Toll-like receptors.
Pathogen-associated molecular pattern (PAMP)
The specific site on an antigen that is recognized by an antibody. Also known as an epitope.
Antigenic determinant (epitope)
the major antibody in serum. IgG posses two antigen binding sites.
Immunoglobin G (IgG)
T cells that trigger cell death via apoptosis in cells that display foreign antigens on class I MHC proteins.
Cytotoxic T lymphocyte
A defense system that that responds to specific features present only in a given pathogen that is comprised of a humoral and cellular component. In the humoral immune response, antibodies function as recognition elements that bind to foreign molecules and serve as markers signaling foreign invasion. In the cellular immune response, cytotoxic T lymphocytes destroy cells that have been invaded by a pathogen.
Adaptive immune system
A family of receptors that recognize specific features present in most pathogens and yet not respond to materials normally present in the host.
Toll-like receptor (TLR)
a system for cellular recognition of foreign substances that employs cell-attached T-cell receptors to eliminate cells infected by a pathogen or to elicit a particular antigenic response by stimulating B-lymphocyte antibody production.
Cellular immune response
the carboxyl terminal end of an IgG light chain or an IgG heavy chain. For many antibodies these portions of the polypeptide chains have amino acid sequences that are very similar to one another; a light chain has one constant region, whereas a heavy chain has three such regions, each of which specifies a compact domain in the native immunoglobulin molecule.
Constant region
a 25-kd polypeptide that is one of two types of chains found in immunoglobulin G. Each L chain consists of a variable region and a constant region, and each chain is linked by a disulfide bond to a heavy chain.
Light (L) chain
the major class of antibodies in external secretions, such as saliva, tears, bronchial mucus and intestinal mucus.
Immunoglobin A (IgA)
the first class of antibodies to appear in the serum after exposure to an antigen. IgM posses10 antigen binding sites.
Immunoglobulin M (IgM)
an antibody of unknown function.
Immunoglobin D (IgD)
an antibody that confers protection against parasites. IgE also initiates allergic reactions.
Immunoglobin E (IgE)
mobility imparted to IgG antibodies by a flexible polypeptide that joins the Fc and the two Fabunits. Such mobility enhances the formation of antibody-antigen complexes.
Segmental flexibility