[The relationship between tuberculosis, vitamin D, potassium and AIDS. A message for South Africa?].

The converging epidemics of tuberculosis and acquired immunodeficiency syndrome (AIDS) in the RSA and their expected catastrophic interaction afford an ideal opportunity for well-planned and essential research by clinicians, molecular biologists, epidemiologists and other health workers. The enigmatic relationship between tuberculosis, vitamin D and calcium is a field of study which should be considered urgently. An optimal vitamin D status not only assures sound calcium-phosphorus homeostasis, but is also essential for maximal immune competency. Hypovitaminosis D probably predisposes towards vulnerability to tuberculosis due to deficient monocyte-macrophage function. In contrast, hypervitaminosis D can correct this deficiency, but would do so at the cost of both B- and T-lymphocyte efficiency. One example of such a state is the endogenous over-production of activated vitamin D by gamma-interferon-activated monocytes, tissue macrophages and granulomatous tissue in tuberculosis. This would not only cause the coincidental hypercalcaemia, but may also complicate the effective co-ordination of monocyte-lymphocyte interaction and consequently compromise an appropriate immune response. It can reasonably be expected that the raised plasma interferon levels in the AIDS patient may trigger similar vitamin D-related pathophysiological processes. It is proposed that the ideal situation for enhanced vulnerability to tuberculosis in the AIDS patient will have been created if the known destructive effects of the human immunodeficiency virus on CD4-positive lymphocytes act synergistically with the vitamin D-mediated complications listed above.