The current definition of IRIS includes five criteria: (1) confirmation of HIV infection, (2) temporal association between IRIS development and HAART initiation, (3) specific host responses to HAART, such as a decrease in plasma levels of HIV RNA and an increase in CD4 + cell count, (4) clinical deterioration characterized by an inflammatory process, and (5) exclusion of other causes. This evidence concerns the gene CD4 and HIV infectious disease.