Bacteria have plenty of ways to combat the viruses that plague them, called phages. The CRISPR-Cas system and restriction enzymes that cleave phage DNA are the best understood, but there are others.

Phase I/II study of intermittent all-trans-retinoic acid, alone and in combination with interferon alfa-2a, in patients with epidemic Kaposi's sarcoma. On the single-dosing 1-hour schedule, CNS ...