The opportunistic infections that are associated with HIV do not
cause ADC. Instead, HIV causes ADC. However, researchers do not
know how the virus damages the brain cells. HIV may affect the
brain through several mechanisms. The HIV proteins may damage
nerve cells directly or indirectly. Many researchers suggest
that HIV damages the neurons indirectly. According to some
researchers, HIV either infects or activates macrophages and
microglia. These cells then produce toxins that can stimulate a
series of reactions, which instruct neurons to kill themselves
(abnormal neuronal apoptosis). The infected macrophages and
microglia also appear to produce chemokines and cytokines
(proteins that mediate and regulate immunity, inflammation and
hematopoiesis), which can also affect neurons, as well as
astrocytes. The affected astrocytes, which normally protect and
nurture neurons, may now end up damaging them. While the
progression of dysfunction is variable, it is regarded as a
serious complication and, if left untreate