What is an Antibody? An antibody is a protein produced by your
white blood cells. Antibodies are also called Immunoglobulins
Antibodies detect foreign substances in your body (i.e. poison ivy
toxin, polio, herpes, diptheria toxin) Antibodies initiate an
immune response by activating production of killer T cells which
destroy invader Over the course of an infection, new antibodies are
made that become better and better at binding foreign substance (If
binding is better, what happens to the Kd?
____________________________) Once your body has mounted an immune
response to a substance, it will always remember it so the next
time you become infected, you immediately make the tight binding
antibodies to rapidly destroy the foreign substance. This memory is
made possible through cells that are stored in your bone marrow
store(called memory cells)
Slide 5
Structure of an Antibody Each antibody is a tetramer (H 2 L 2 )
___ copies heavy chain (red) (H) ___ copies of light chain (blue)
(L) The foreign substance (called _______) binds at the tips of the
arms in the region between the N termini of the H and L
polypeptides. The L chain folds into two domains: V L with variable
sequence and C L with constant sequence. The H chain folds into 4
domains: one variable V H and 3 constant domains _____________
connect the 4 chains A sugar binds to the ___________chain
Slide 6
Structure of an Antibody Each antibody is a tetramer (H 2 L 2 )
Two copies heavy chain (red) (H) Two copies of light chain (blue)
(L) The foreign substance (called antigen) binds at the tips of the
arms in the region between the N termini of the H and L
polypeptides. The L chain folds into two domains: V L with variable
sequence and C L with constant sequence. The H chain folds into 4
domains: one variable V H and 3 constant domains Disulfide bonds
connect the 4 chains A sugar binds to the heavy chain
Slide 7
Remember that Polypeptides Fold in Two Ways: Alpha helices at
left Beta strands below. One strand of beta structure is
represented by a thick arrow with the head towards the C
terminus
Slide 8
IgGs are Mostly Beta Structure
Slide 9
Slide 10
Constant Both the constant and variable domains - strands
Constant domain: Seven strands are labeled A-G (see disulfide)
Variable domain Nine Strands Variable domain binds antigen through
loops CDR1-CDR3 Variable
Slide 11
Antigen binding site at tip of each arm Looked at from the
top,the combining site, with the six CDR regions, contains
possibility for lots of specificity. Antigen Binds here
Slide 12
Blood Clots Using the Fibrinogen Fibrinogen The building block
of blood clots is fibrinogen hexameric molecule 2 2 2 Overall
structure for one molecule has two edges (C- terminal) D regions),
one middle (N-terminal E region), and two middle regions ( with
three - helices When fibrinogen clots, connections are made from
one hexamer to the next as shown in B, C, and D