How do antibiotics affects the normal flora of the large intestine? Why are the human cells that line the large intestine not destroyed by the...

Antibodies come in contact with microbes that reside in
the large intestine as the chemicals are ingested as tablets and their absorption starts
in the intestines where the outer coating of the tablets is
dissolved.

As the concentration of antibodies is
particularly high in the intestines, the microbes in the large intestine are affected in
a very adverse manner by the antibodies. The result is a rapid reduction in the number
of bacteria.

This is not good for our health as a very
large number of good bacteria live in the intestines. They help in
the digestion of food and in the absorption of many vital nutrients. The
good bacteria also keep the number of harmful bacteria in check.
The affect of antibodies is a disruption in the process of digestion. Over a prolonged
period of time it can lead to deficiency of nutrients like vitamin K and the B vitamins.
The chances of infections due to the bad bacteria also go
up.

Human cells in the intestines are not destroyed by
antibodies as antibodies are substances that selectively interfere in the chemical
processes of bacterial cells. As these processes do not take place in human cells in the
same way as they do in the target bacteria, the human cells do not suffer any
damage.