How do immunosuppressive drugs increase the likelihood of success of a transplant, yet place a patient at a higher risk of contracting infections?

Question

I would like to know it in a more detailed way thank you.

Answer 1

Hi Cherry M.,

I don't quite know at what level of detail to craft a response. But in general terms: transplants are selected so as to match antigenic sugars and proteins of the recipient. The major consideration on this is Landsteiner-Donath blood type (ABO), which are types of surface-bound sugar on blood cells (or other tissue surfaces); however, your blood bank technicians characterize many more types of antigenic activity. Some terms you might look up include Rh, Duffy, and Kell. The more of these antigens (including major histocompatibility locus ones for organs) you match up, in general the better is the lifetime for transfused blood cells (up to their 88 day normal duration before breakdown). And that is before considering whatever viruses may be present, and so on. Because organs are seldom completely antigenically identical from donor to recipient, without chemical intervention the transplanted organ would eventually (but usually, promptly!) be recognized as foreign by the recipient's immune system, and rejected, causing the organ (and likely the recipient) to die. When immunosuppressive drugs are administered, they interfere with the body's ability to recognize anything as foreign. That's a problem, b/c bacteria, viruses, and other agents are continually trying to invade your body, and are kept at bay by your immune system, among other mechanisms. You have comparable numbers of bacteria in your gut as you have body cells of your own, for example. And they would largely be capable of colonizing your gut tissues, and then the rest of your body ,,,, -- not a pleasant scenario. Also you inhale substantial numbers of airborne bacteria, fungi, etc. every day, capable of causing pneumonia as they colonize your lungs. So you need additional anti-infection monitoring and treatments, because you can't permit your body to have its normal level of vigilance. Your immune system is incidentally capable of becoming hyperreactive as well, mistaking parts of you as foreign -- see Lyme Disease, and Johnson-Stevens Syndrome, for example; that's fortunately rare (unless you live in the eastern US, for Lyme).

Hope that gets you in the right direction for further inquiry,

-- Cheers, -- Mr. d.