Chapter 5 Flashcards
antibodies or immunoglobulins are a family of structurally related glycoproteins produced where?
membrane-bound or secreted form by B
lymphocytes.
membrane bound antibodies serve as receptors that mediate what?
the antigen-triggered activation of B
cells.
Secreted antibodies function as what?
mediators of specific humoral immunity by engaging various effector mechanisms that serve to eliminate the bound
antigens.
the antigen binding regions of antibody molecules are what?
highly variable, and any one individual has the
potential to produce more than 1011 different antibodies, each with distinct antigen specificity
all antibodies have a common symmetric core structure of what?
two identical covalently linked heavy
chains and two identical light chains, each linked
to one of the heavy chains. Each chain consists of
two or more independently folded Ig domains
of about 110 amino acids containing conserved
sequences and intrachain disulfide bonds
the N terminal domains of heavy and light chains form the what?
V regions of antibody molecules, which
differ among antibodies of different specificities
The v regions of heavy and light chains each contain what?
three separate hypervariable regions of
about 10 amino acids that are spatially assembled
to form the antigen-combining site of the antibody
molecule
What are the antibody classes?
IgM, IgD, IgG, IgE, and IgA. Both
light chains of a single Ig molecule are of the same
light chain isotype, either κ or λ, which differ in
their single C domains
Most of the effector functions of antibodies are
mediated by the C regions of the heavy chains, but
these functions are triggered by what?
binding of antigens to the spatially distant combining site in the
V region.
how are monoclonal antibodies produced?
from a single
clone of B cells and recognize a single antigenic
determinant
what are antigens?
substances specifically bound by
antibodies or T lymphocyte antigen receptors.
Antigens that bind to antibodies represent a wide
variety of biologic molecules, including sugars,
lipids, carbohydrates, proteins, and nucleic acids
what are macromolecular antigens?
contain multiple epitopes, or determinants, each of which may be recognized by an antibody
linear epitopes of protein antigens consist of what?
a sequence of adjacent amino
acids, and conformational determinants are formed
by folding of a polypeptide chain
the dissociation constant (Kd) calculated from binding
data generally represents what?
The affinity of the interaction between the combining site of a single antibody molecule and a
single epitope
What are polyvalent antigens?
contain multiple identical epitopes to which identical antibody molecules
can bind. Antibodies can bind to two or, in the case
of IgM, up to 10 identical epitopes simultaneously,
leading to enhanced avidity of the antibody-antigen interaction
The relative concentrations of polyvalent antigens
and antibodies may favor what?
the formation of immune
complexes that may deposit in tissues and cause
damage
Antibody binding to antigen can be highly specific,
distinguishing what?
small differences in chemical structures, but cross-reactions may also occur in which
two or more antigens may be bound by the same
antibody
Several changes in the structure of antibodies
made by one clone of B cells may occur in the
course of an immune response. B cells initially
produce what?
only membrane-bound Ig, but in activated B cells and plasma cells, synthesis is induced
of soluble Ig with the same antigen-binding specificity as the original membrane-bound Ig receptor
Changes in the use of C region gene segments
without changes in V regions are what?
are the basis of
isotype switching, which leads to changes in effector function without a change in specificity
Point
mutations in the V regions of an antibody specific
for an antigen lead to what?
lead to increased affinity for that
antigen (affinity maturation)
