Our immune system works pretty much the same
way as the immune system of almost every other
vertebrate (animal with a backbone and skull).
We have some passive systems like a tough
skin, mucus, friendly bacteria, saliva, and such
that help us keep germs from entering our bodies.
Stomach acid helps to kill the germs in food. We
have an inflammation response that happens when we
have an injury. A bunch of cells go to the cut and
start eating any germs they find. Blood and other
fluids go to the spot to bring resources and more
cells. Our skin gets warm, swells, and gets darker
(or red if we have pale skin). The swelling also
There are also cells in our body that find
invaders and kill them directly or by making
antibodies that stick to them.
I think I know why you’re asking why animals
have a stronger one. After all, we wash our hands
after using the bathroom and before we eat.
Meanwhile a dog will drink right out of the toilet
or eat garbage it finds on the sidewalk. Vultures
each animals that have been rotting in the sun for
days. The dogs and the vultures seem to be
fine. What’s going here?
One thing that may be going on is that dogs
without strong immune systems probably die young.
Dogs with genes for strong immune systems are more
likely to survive and pass along their genes. A
different kind of adaptation can happen during our
lives. The same is true for vultures.
Immunity can also improve during our lives.
When individuals (dogs, humans, or vultures) are
exposed to germs, our immune systems not only
respond right away, they have memory cells that
keep the body alert for that germ in the
future. It’s kind of like a police station
keeping wanted posters on the wall. Dog and
vulture immune systems have been introduced to a
lot more germs than our immune systems have been.
A research team looked at the genetics behind the
immune system of one species of vulture and found
a few things that help vulture eat a pretty nasty
diet. For one thing, their stomachs make a lot
of very strong acid. Their stomachs are at
least 10 times more acidic than our stomachs.
Sometimes 1000 times as acidic. Some vulture live
on bones that their stomach acid break down.
Vulture genes also seem to code for cells in the
immune system that are especially good at finding
and destroying germs. Another thing vultures have
going for them is that their bald heads and necks
may also help keep them clean. Feathers dipped in
dead things day after day would get pretty nasty.
Vultures also eliminate all over themselves and
their wastes kill germs. Amazing, right?
In places where lots of people and vultures
live, diseases in humans go up when the vulture
population goes down. Can you imagine why?
Hint: what happens to cities when the
garbage workers go on strike?
If you are interested in studying immunity, you
can be an immunologist.
Thanks for asking,