Immune cells are essential for fighting off infections and diseases in the human body. But how do they find their way to the right places? A new study reveals that immune cells can create their own chemical cues to navigate in complex environments, challenging the previous notion that they only follow existing signals.
Immune cells are not passive followers
Immune cells need to move quickly and efficiently to reach their targets. They are guided by chemokines, a class of signaling proteins that form chemical cues called chemokine gradients. Chemokines are produced by various tissues, such as the lymph nodes, where immune cells interact and initiate an immune response.
The traditional idea has been that immune cells recognize their target by following existing chemokine gradients. In other words, the cells following these cues have been seen as passive actors, which is not the case in reality.
A new study conducted by InFLAMES researcher Jonna Alanko has discovered that immune cells do not just passively follow the chemical cues in their environment. Quite the contrary, they can also shape these cues and navigate in complex environments in a self-organized manner.
Immune cells consume chemokines
Alanko focused on the movement and navigation of dendritic cells (DCs), a type of immune cell that functions as a messenger between the innate and adaptive immune responses. DCs scan tissues for intruders, locate an infection site, recognize it, and then migrate to the lymph nodes with the information.
DCs have receptors called CCR7 that can sense a chemokine signal. Alanko found that DCs do not only register a chemokine signal with their CCR7 receptor, but they also actively shape their chemical environment by consuming chemokines. By doing this, the cells create local gradients that guide their own movement and that of other immune cells.
The researchers also discovered that T-cells, another type of immune cell, can benefit from these self-generated gradients to enhance their own directional movement.
Implications for human health
The study, published in Science Immunology, challenges the earlier notions about the movement of immune cells and enhances our knowledge of the immune system. It also offers potential new approaches to improve human immune response.
“When immune cells are capable of creating chemokine gradients, they can avoid upcoming obstacles in complex environments and guide their own directional movement and that of other immune cells,” explains Alanko.
The study was conducted by researchers from the Institute of Science and Technology Austria (ISTA) and the University of Turku. It was supported by the Academy of Finland and the European Research Council.