The Structure
of Antibodies
We have previously stated that
antibodies are a type of protein. So, let us first
examine the structure of proteins.
Proteins are made up of amino acids.
Twenty different types of amino acids are arranged
in different sequences to form different proteins.
This is similar to making different necklaces by using
beads in twenty different colours. The main differences
among proteins are due to the sequence of these amino
acids.
Yet there is an important point to
remember: Any error in the amino acid sequence makes
the protein useless, and even harmful. Therefore,
there is no room for even the smallest error in the
sequence.
So, how do the protein factories in the cell know
in which sequence to arrange the amino acids they
contain, and which protein to produce? The instructions
for each of the thousands of different types of proteins
are encoded in the genes found in the genetic data
bank in the cell nucleus.
Therefore, these genes are required
for the production of the antibodies which are a type
of protein.
There is a very important miracle
here. There are only one hundred thousand genes in
the human body compared to the 1.920.000 antibodies
that are produced. This means that nine hundred thousand
genes are missing.
Then how is it ever possible that
such a small number of genes can produce antibodies
about ten times their value? The miracle is revealed
at this point. The cell combines the hundred thousand
genes it contains in different combinations to form
new antibodies. It receives the information from some
genes and combines it with the information in other
genes and makes the required production according
to this combined information.
1,920,000 different
antibodies are formed as a result of 5,200 different
combinations.4 This process represents
a wisdom and planning that are too great for the human
mind to comprehend, let alone design.
An unlimited number of combinations
can be made with the use of one hundred thousand genes.
The cell, however, uses, with great intelligence,
only 5,200 basic combinations and produces 1,920,000
specific antibodies. How has the cell learned to make
the right combinations out of these unlimited possibilities
to form the required antibodies?
1. Variable
region of light chain, 2. Contant region of light
chain, 3. Carbonhydrate group, 4. B Cell, 5. Antibodies,
6. Constant region of heavy chain, 7. antigen-binding,
8. Variable region of light chain, 9. Antigen, 10.
Activated B-cells, 11. Plasma cell, 12. Free antibody,
13. Memory cell
Making the correct combinations out
of an infinite number of possibilities aside, how
has the cell got this idea of making combinations?
Moreover, the produced combinations
serve a certain purpose, and aim to produce an antibody
that would eliminate the antigen that enters the body.
Therefore, the cell also knows the properties of the
millions of antigens entering the body.
No intellect in this world can produce
a design of such unparalleled perfection. But cells
only the size of a hundredth of a millimeter can do
so.
So, how has the cell learned such
a special system?
The truth is that no cell has the
opportunity to "learn" a biological function in the
real sense. This is because the cell does not possess
the ability to perform such an act at birth, nor has
it the chance to develop the required skill during
the rest of its lifetime. In such cases, it is a prerequisite
that the system in the cell should be ready and complete
at the beginning of life. The cell neither possesses
the skill to learn such combinations, nor does it
have the time to learn them, as this would cause it
to fail in stopping the antigens entering the body
and the body would lose the war.
The fact that a system that baffles
mankind, even at the point of comprehending it, has
been placed in a cell which has no ability to think
and reason, has a very special meaning. This is the
reflection of the uniqueness of the creation of God,
the All-Knowing, in a tiny cell. In the Qur'an, it
is stated that God's superior wisdom encompasses
everything:
...They cannot grasp
any of His knowledge save what He wills. His Footstool
encompasses the heavens and the earth and their preservation
does not tire Him. He is the Most High, the Magnificent.
(Surat al-Baqara: 255)
If you were to design an antibody
molecule, how would you do it? You would first have
to carry out comprehensive research before deciding
on the shape of the molecule. Surely you could not
shape it randomly without an exact knowledge of its
duty. Since the antibodies you are going to produce
will make contact with antigens, you would have to
be very well informed about the structure and specifications
of the antigen, too.
Eventually, the antibody you will
produce has to have a special and unique shape at
one end. Only then can it bind to an antigen. The
other end of it has to be similar to other antibodies.
This is the only way the antigen destructing mechanism
can be activated. As a result, one end has to be standard,
while the other has to be different from the others
(which come in more than one million different types).
Human beings, however, have been
unable to design an antibody, despite all the technology
at their disposal. The antibodies produced in the
laboratory environment are either derived from antibody
samples taken from the human body, or the bodies of
other living beings.
4-
Scientific American, September 1993, p. 54