Newly identified cell type uncovered in the thymus

In a collaboration between researchers in Riverside, California, and Israel, Professor David Lo and his graduate student, Diana Del Castillo, were sought after for their expertise on Microfold cells (M cells). These specialised cells are primarily known for their role in the intestinal epithelium. However, the team discovered similar cells in the thymus, an organ crucial for producing lymphocytes that are vital for the immune system’s function. The research paper was published in Nature.

M cells act as immune gatekeepers, delivering antigens to the immune system in organs like the intestines and lungs, playing a pivotal role in immune system development. The Israeli researchers, led by Jakub Abramson at the Weizmann Institute of Science, conducted a study involving mice to explore the thymic epithelium before consulting Professor Lo.

Lo’s research had previously focused on M cells in the gut and airways, so he found the discovery of M-like cells in the thymus intriguing. Del Castillo, under Lo’s guidance, had been studying mucosal tissues in mice, which enabled her to provide insights into the newly found thymic M cells’ location and function.

These thymic M cells are unique, limited to specific regions in the thymus, and exhibit distinct associations with different cell types and functions. Their discovery raises questions about how they compare to M cells found elsewhere in the body and what sets them apart in terms of function and location.

The thymus has long fascinated immunologists due to its central role in immune system development. The thymus is responsible for producing lymphocytes crucial for protecting against infections.

Lo noted that the thymic M cells closely resemble those in the gut and airways but have different developmental origins. They capture viruses and pathogens entering the airways and present them to the immune system for a response, like their counterparts in other organs.

The findings revealed that these new cells are scattered in the thymus’s medullary region, shedding light on their role in regulating lymphocyte training within this organ.

The researchers were surprised to find that many processes shaping immune responses in various parts of the body appear to mirror those in the thymus. These early cell interactions and developments observed in the thymus were unexpected and intriguing.

The thymus also plays a crucial role in ensuring that lymphocytes do not mistakenly attack the body’s own tissues, with these decisions being made in the thymic medulla. The newly discovered M cells are part of this decision-making process and exhibit similarities to interactions observed in the peripheral immune system’s early stages.

Lo suggests that thymic M cells may undergo training in the thymus to prepare for their later function in the periphery, facilitating effective communication and interaction with other cells when needed. This discovery opens new avenues for understanding immune system development and regulation.