It is well known that chronic hyperglycaemia (raised blood sugar) impairs some host defence mechanisms and is associated with increased mortality due to infection in diabetic patients. Several studies have now confirmed that hyperglycaemia per se or the metabolic abnormality of diabetes is sufficient to explain the impaired immune response in patients responding to infections. There are multiple defects in the immune function in diabetics unlike people without diabetes.
There are normally 4000-11000 white blood cells per microlitre of human blood. Of these, the granulocytes (polymorphonuclear leukocytes, PMNs) are the most numerous. Acting together with lymphocytes and monocytes, these cells provide the body with powerful defences against viral, bacterial and parasitic infections.
The PMN granulocytes (a particular type of white blood cells) represent the host's first defence barrier against bacterial agents. An abnormality in the antibacterial function of these white blood corpuscles is a very important factor. In diabetic patients these cells show various defects in their function.
PMN cells are attracted to the site of infection by various substances secreted by microorganisms. Cells from diabetic patients have an impaired movement, especially when the diabetes is poorly controlled.
The PMN type of white blood cells also show defect in ingestion of the microorganisms, which is an important step in fighting infections.
Uncontrolled diabetes also leads to a decrease in the killing activity of PMN. However, normalisation of blood glucose levels following intensive insulin therapy improves killing activity within 48 hours.
Diabetics also have other important defects in the immune system like reduction in the T lymphocytes (helper cells), a type of white blood cell. These cells normally help in cell-mediated immunity.
Serum immunoglobulin levels have been reported to be reduced in diabetic patients compared to normal subjects. Moreover, diabetics have reduced blood circulation to the extremities. This impairs wound healing particularly in the lower extremities. The antibiotics will be unable to reach the target tissues due to the poor blood supply.
Courtesy : The Hindu
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