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J. John Cohen, MDCM, PhD

How did the last smallpox person not infect unimmunized newborns?

By keeping away from them, under doctor’s orders. Also, remember that newborns benefit from their mother’s antibodies, both those passed across the placenta and those provided in milk, if she nurses the baby.

When pus develops because your lymph nodes are swollen what does it look like? And where is it mostly found?

Wherever the infection is, the antibodies we make will find it and bind to the infecting organisms. Then Complement is activated, and it attracts millions of the white blood cells called neutrophils. They are pus. So it appears where the infection is: in your throat, or that finger you cut, or that zit, or…

I was born in Germany in 1989, they don't allow me to donate blood because I was born during the mad cow disease 'era'. Why is that? I know I don't have mad cow.

Well, they tell me that mad cow disease has a very long incubation period, so they don’t know absolutely that you won’t get it (though the odds are less than winning at Powerball). Maybe eventually they will judge that you are not any longer at risk to get it and will allow you to start again. And unfortunately, at present we have no test for whether anyone is carrying mad cow disease until they get sick.

What do Vit.C and zinc do for the immune system? Can any other vitamins help 'boost' the immune system?

Nope. All you need is the amount recommended for general health. There are no “immune system boosters,” no matter what the ads say. Just like [CENSORED] doesn’t make a good truck, even though big tough guys on TV say they do!

Might the proliferation of vaccines over the last century be related to the jump in asthma & autoimmune disorders?

It is always possible, though no one has seen the slightest sign of a correlation between the two. You could just as well speculate that the increase of numbers of teams in the NHL was the real cause.

Is it possible to “grow” out of food allergies as an adult (when the immune system weakens)?

Yes, but it’s not the immune system weakening; that remains very good into old age. It is likely that continued exposure to a varied diet, and other changes we don’t know about, contribute to eventual increase in activity of “regulatory T cells” that damp down the allergic response.

If kids benefit from ingesting dirt and germs at what age does that exposure stop benefiting the body?

We simply don’t know. However, in a startling paper in 2005, some researchers reported that they fed whipworm eggs to adults with inflammatory bowel disease, with very impressive results. This has led to feverish research and also, unfortunately, to a bunch of quacks offering worms to treat all sorts of conditions.

Can you explain MAST cells and allergic reactions?

Pretty, eh? Those black granules are full of histamine. The cell is coated with allergic antibodies, which trigger the release of the histamine and other stuff when you next get exposed to whatever it is you’re allergic to.

Is it true that an Apple a Day keeps the Doctor away?

Absolutely. Apples have many important properties, including keeping elephants away. Since I have been putting apples in my fridge, I have never once found elephant footprints in the peanut butter. Isn’t that amazing?