Breakthrough! Novel Antigen-presenting Immune Cells Play A Vital Role in Respiratory Infections

A study published in the Journal of Immunology reported that an international team of scientists identified a new type of antigen-presenting immune cells that are part of the dendritic cell family and play a key role in presenting antigens to other immune cells during respiratory virus infection. Also, it can explain how the plasma in the recovery period helps to enhance the immune response of patients with viral infections.

When our body faces an infection, its reaction is inflammation and fever. This is a signal that the immune system works and causes the activation of many cells, just like soldiers in the military. Dendritic cells (DCs) are the generals of this army. They can accurately activate and instruct soldiers to kill infected cells by presenting antigens produced by "invaders" to cells of the immune system.

There are several types of dendritic cells that perform antigen presentation functions in the body. The first type is conventional dendritic cells, which will continue to scan the body for dangerous intruders even when there is no infection. When infection causes inflammation, another subset of dendritic cells appears from the inflammatory monocytes. Since it is easy to prepare monocyte-derived dendritic cells isolated from human blood in vitro, it has always been considered that these cells are very important antigen-presenting cells. However, clinical tests using monocyte-derived dendritic cells to treat cancer are disappointing.

Studies have shown that monocyte-derived dendritic cells are poor antigen presenting cells, however, due to a wrong identification, it was mistakenly considered to have these functions.

The scientists used single-cell technology to study mice with viral respiratory infections (mouse pneumonia virus and influenza virus). This single-cell isolation method allows them to separate monocyte-derived cells from other dendritic cells in response to infection. They found that monocyte-derived dendritic cells do exist, but do not present antigen. The reason for all these confusions in the past was the emergence of a new type of dendritic cells of similar appearance, called inflammatory type 2 conventional dendritic cells, or inf-cDC2, which combines some of the best characteristics of monocytes, macrophages and conventional dendritic cells to induce the best form of immunity.

Bart Lambricht, one of the researchers said that, “This is a big surprise for us. We all know that monocyte-derived cells are good antigen presenting cells, especially when there is inflammation. Now, we demonstrated that it is actually a new mixed dendritic cell type and did all the work. This really changed our understanding of the immune system and is very important for understanding respiratory viral infections and other inflammatory diseases. "

The power of single-cell sequencing has finally cracked the code of complex dendritic cells. Many conflicting discoveries of the past 20 years are now more meaningful. This also brings huge therapeutic opportunities, because it is now possible to design a vaccination strategy to trigger the formation of inf-CDC2, thereby generating a stronger antiviral immune response.

With single-cell technology, scientists are able to combine all the findings of the past few years and identify the different cell types involved. Looking ahead, we will be very interested to see how these inf-cdc2 are produced under other inflammatory conditions and how they may become therapeutic targets.