The immune system protects the body from threats. Proteins and receptors on the surface of immune cells act as communication tools, helping these cells navigate and respond to various challenges. One such protein, C-C chemokine receptor type 6, or CCR6, is an important protein in this network, guiding immune cells to specific locations to initiate or regulate defense.
Understanding CCR6
CCR6 is a protein on the surface of immune cells, functioning as a chemokine receptor. Chemokine receptors are a type of G protein-coupled receptor that respond to signaling molecules called chemokines. CCR6 uniquely binds exclusively to a single chemokine, known as CCL20. This binding triggers internal signals within the cell.
CCR6 is present on several types of immune cells, including T cells, B cells, immature dendritic cells, natural killer T (NKT) cells, and neutrophils. It is notably expressed in tissues like the appendix, spleen, lymph nodes, and pancreas, with lower levels in the thymus, colon, and small intestine.
CCR6’s Role in Immune Cell Guidance
The primary function of CCR6, through its interaction with CCL20, is to direct the movement of specific immune cells. This interaction acts like a “GPS” for cells, guiding them to particular tissues. For instance, CCR6 helps organize lymphoid tissues like Peyer’s patches and mesenteric lymph nodes by recruiting immune cells, including dendritic cells and macrophages.
CCR6 is important for the migration of T helper 17 (Th17) cells and regulatory T (Treg) cells. Th17 cells promote inflammation, while Treg cells suppress immune responses and maintain balance. Both T cell subsets express CCR6, and Th17 cells also produce CCL20, which attracts both Th17 and Treg cells to sites of inflammation or infection. This targeted migration ensures localized and efficient immune responses. For example, CCR6-mediated signals are involved in immune responses to microbes in the intestinal lining.
CCR6 and Its Impact on Health
The proper functioning of CCR6 maintains immune balance, and its dysregulation can contribute to various health conditions. In autoimmune diseases, where the immune system mistakenly attacks the body’s own tissues, CCR6 guides inflammatory immune cells to affected sites. For instance, increased CCR6 expression and its interaction with CCL20 are observed in conditions like inflammatory bowel disease, rheumatoid arthritis, psoriasis, and multiple sclerosis. Inhibiting this interaction can reduce immune cell migration to inflamed tissues, potentially lessening disease severity.
CCR6 also contributes to the body’s defense against infections. It directs immune cells to infected areas, which is important for clearing pathogens. For example, the CCR6/CCL20 axis has been implicated in the immune response to SARS-CoV-2, the virus causing COVID-19, by driving T cell recruitment to the lungs and contributing to inflammation.
In the context of cancer, CCR6 has an emerging role. The CCR6/CCL20 axis can influence tumor growth and spread, with increased CCR6 expression observed in various cancers, including colorectal, breast, and pancreatic cancers. This interaction can promote the migration and proliferation of cancer cells and affect the tumor’s surrounding environment by influencing immune cell activity. Targeting CCR6 could disrupt these processes, offering new avenues for cancer therapies.