- Genetic testing DNA from blood or cheek cells may be examined for mutations or deletions that affect chemokines, cytokines and a family of enzymes called caspases. Chemokines and cytokines are important mediators of the immune response. Alterations in the genes for some of these substances influence HIV infection. Caspases regulate the process of cell death, known as apoptosis. Caspase gene variations may determine the rate of cell death in HIV-infected persons, and therefore, the rate of HIV progression. Patients with abnormalities of any of these genes may be invited to join other studies of the role of genetic defects in HIV infection.