It is also important in pathological conditions such as anti-cancer drug-induced cell death in tumours, progressive cell death and depletion of cluster of differentiation 4 (CD4+) cells in Acquired Immunodeficiency Syndrome (AIDS), cell deaths due to injurious agents (like hypoxia, radiation and thermal injury), cell death in heart diseases like myocardial infarction, cytotoxic T cell-induced cell death, some forms of virus-induced cell death (e.g. Hepatitis B or C), etc. This evidence concerns the gene CD4 and AIDS.