Neutrophil interactions with the sexually transmitted parasite implications for immunity and pathogenesis.

Trichomoniasis is the third most common sexually transmitted infection in humans and is caused by the protozoan parasite, (). Pathogenic outcomes are more common in women and generally include mild vaginitis or cervicitis. However, more serious effects associated with trichomoniasis include adverse reproductive outcomes. Like other infectious agents, pathogenesis from infection is predicted to be the result of both parasite and host factors. At the site of infection, neutrophils are the most abundant immune cells present and probably play key roles in both parasite clearance and inflammatory pathology. Here, we discuss the evidence that neutrophils home to the site of infection, kill the parasite, and that in some circumstances, parasites possibly evade neutrophil-directed killing. , the parasite is killed by neutrophils using a novel antimicrobial mechanism called trogocytosis, which probably involves both innate and adaptive immunity. While mechanisms of evasion are mostly conjecture at present, the persistence of infections in patients argues strongly for their existence. Additionally, many strains of harbour microbial symbionts or , which are both predicted to impact neutrophil responses against the parasite. Novel research tools, especially animal models, will help to reveal the true outcomes of many factors involved in neutrophil- interactions during trichomoniasis.