Page 206 - The Miracle in the Cell Membrane

he mother's immune system does not reject the for-
eign tissue—the embryo, which represents a foreign
substance—inside her body. In the same way that for-
eign tissue is rejected by organ transplant patients, so
the embryo should be regarded as a foreign body by
the mother's immune system. Half of the unborn baby's genes
come form the mother and half from the father, and every com-
pound from the father should be regarded as an antigen or attack-
er. Therefore, one would expect the defense system to set about
eliminating the embryo.
However, the mother's body does not declare war on the embryo,
because the components of the immune system in her blood are not
permitted to pass through the placenta; and so these elements can-
not perceive the embryo as a foreign tissue and destroy it.
The defensive cells standing guard in the body become acquainted
with foreign substances before moving to destroy them. To do this,
they use molecules known as the major histocompatibility complex
(MHC) in the cell membrane. Since the embryo's cells do not have the
MHC molecules, they are not identified by the mother's defense cells.
However, the absence of MHC molecules in these cells can lead to natu-
ral killer cells determining that these cells are abnormal and destroying
them. Therefore, the embryo cells carry a non-classical type of molecule
in their cell membranes: human leukocyte antigen G (HLA G).
Therefore, the mother's defense system does not perceive the embryo's
HLA G as a foreign substance, and the natural killers ignore it. Yet in addi-
tion to these methods, chemical signals are also employed. The placenta pro-
duces a series of chemical signals that affect the mother's defense system,
which is why the mother is more exposed to infections during pregnancy.
If this exception were to apply to any other foreign substance in the mother's
body, then she would be exposed to lethal dangers. On the other hand, if this
exception did not apply to the embryo, then its survival would be impossible. As
revealed in the verse "He is Allah—the Creator, the Maker, the Giver of Form. . . .
" (Surat al-Hashr, 24), every detail reveals the perfection in our Lord's creative
artistry.

(Bea Perks, Andrew Coulton, "The Great Escape," New Scientist, Vol. 171, No. 2308, 15 September,
2001.)

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