Sleep is a vital part of our lifestyle that is in many ways an enigma. We know it is highly important and we know it performs many crucial functions in the body. However what we do not fully understand is precisely the full extent of its roles and things like dreaming are still very much a mystery to us (though many interesting theories on the matter exist!).
However what we do know is that without sleep our body is under a lot of stress and is unable to make its usual 'repairs' and keep us in top condition. During sleep our body produces a lot of hormones such as growth hormone that put us in an 'anabolic' state. This is when our body repairs wounds and builds muscle tissue among other things. Sleep at the same time helps our body to achieve a more relaxed state wherein we experience a lower heart rate and less brain activity. This also then means that our blood pressure drops at least for a while and regular healthy sleep will keep our blood pressure down in the day too. Stress is reduced by sleeping as are other problems and as such our immune system gets a lot of help and benefits from these side effects.
Of course our immune system is what our body uses to fight infection. So by getting healthy sleep we put our immune system in a better position to help us stave off infections and viruses. It follows then that a lack of sleep would result in a greater chance of infection and this is certainly the case. Those who do not get enough sleep then are likely to suffer more from all kinds of problems which will batter the immune system and leave it open to attack from other infections etc. This effect may be even greater for infections in wounds, when you consider that not only will the immune system be less able to deal with foreign bacteria, but that the wounds themselves will also be healing more slowly as a result of the lack of growth hormone.