Abdominal fluid reveals rare immune cells that may limit attacks on tumors

Scientists have discovered a rare type of immune cell in abdominal fluid that may help tumors evade attacks from the body's defense system. In a study published in the journal Science Immunology, researchers used fluid called malignant ascites, which accumulates in the abdomen when cancer spreads, to uncover new immune programs associated with advanced cancer.

Led by a team from the Krantz Family Center for Cancer Research, the study revealed a rare population of dendritic cells expressing a gene called RORC, which were found in 22 out of 23 patients with advanced solid tumors. These cells, called RORC-expressing dendritic cells or RORC DCs, were previously unknown to be linked to cancer.

Although they represent a small fraction of immune cells, their presence suggests they may promote immune tolerance, a mechanism that prevents the immune system from attacking harmless substances or the body's own tissues. This could explain why patients with advanced cancer often do not respond well to current treatments. The researchers believe these cells may play a role in the tolerant immune environment surrounding metastatic cancer, potentially weakening the immune system's ability to target cancer cells.

While the findings do not immediately change clinical care, they open up new avenues for understanding and potentially treating patients with malignant ascites. The study's authors hope their discovery will inspire future research to explore how these cells function and whether they could be targeted for therapeutic purposes.