A team of scientists from Charles University's Faculty of Science has made a significant breakthrough in the study of schistosomiasis, a tropical disease that affects over 250 million people globally. The research focuses on the human blood fluke Schistosoma mansoni, which causes the disease. Traditionally, scientists have studied the proteins secreted by the parasite's eggs in artificial laboratory settings. Now, the team has, for the first time, analyzed these proteins directly within the infected tissues of a living organism. Their findings were published in the journal Frontiers in Cellular and Infection Microbiology. Schistosomiasis is caused by parasitic flatworms called blood flukes. The most dangerous aspect of the disease is the release of eggs by the parasite, which become lodged in the host’s liver or intestine. These eggs secrete substances that trigger an immune response, leading to the formation of granulomas—protective clusters of immune cells that form around the eggs. Over time, this can cause serious health issues, such as liver and spleen enlargement, digestive problems, and even an increased risk of cancer in some cases. To better understand the role of these secreted proteins, the research team used a technique called laser microdissection. This method allows scientists to precisely cut out small sections of tissue surrounding the eggs in infected mice, without damaging the eggs themselves. Using this approach, parasitologist Lucie Jedličková identified 149 proteins that are consistently secreted by the eggs in both the liver and intestine. These proteins were previously studied in artificial environments, which may have distorted the true picture of what the host's body actually encounters during infection. The study also revealed that the proteins secreted by the eggs differ depending on the organ in which they are located and the stage of infection. In the early, acute phase, eggs in the liver release large amounts of molecules that suppress the immune system and break down tissue, while those in the intestine release a more stable set of proteins over time. This difference reflects the eggs' eventual fate: those in the liver remain trapped permanently, while those in the intestine eventually pass out of the body. The findings challenge the assumption that the eggs behave the same way in all organs and highlight the importance of studying them in a more realistic biological context. This research could lead to better understanding and treatment strategies for schistosomiasis.