Theta-defensins are a unique class of antimicrobial peptides found in certain primates, including rhesus macaques. They are characterized by their cyclic structure, which enhances their stability and effectiveness against a variety of pathogens, including bacteria and viruses. These peptides play a crucial role in the immune system by disrupting the membranes of invading microorganisms. Their ability to form a stable ring structure allows them to maintain activity in harsh environments, making them a subject of interest for potential therapeutic applications in treating infections and enhancing immune responses.