Anahita Kodali, Medical Sciences, News, Spring 2020
Figure 1: Dendritic cells (pictured here in green) have a unique shape that is critical to their function. They are very large compared to normal cells. In addition, they have a branched shape. Their size and shape allow them to help the innate and adaptive immunities communicate and also help them capture antigens for T-cell priming.
Image Source: Wikimedia Commons
The cells of the immune system protect the body from infection. There are two types of immunity—innate and adaptive. Innate immunity is the body’s nonspecific and first response to foreign invaders; it is a defense system that acts immediately or very quickly after encountering some pathogen. Innate immunity includes physical barriers (like skin and mucus) as well as certain immune cells (including but not limited to natural killer cells, mast cells, and macrophages)1. Adaptive immunity is the body’s specific and second response to foreign invaders; this response is considerably slower than innate immunity but is very powerful. T-cells and B-cells are both involved in the body’s adaptive immunity2.
Dendritic cells (DCs) are a unique type of immune cells. They do not fit cleanly into either innate or adaptive immunity and are rather considered the sentinels of immunity due to their critical role in bodily defense. Firstly, because DCs are so big, they are able to contact several immune cells at once (both innate and adaptive), linking both types of immunity. Secondly, DCs help direct T-cells, which are considered the core of adaptive immunity. T-cells cannot attack immediately because they need to be primed by its antigen, the toxic foreign substance that needs to be removed. DCs’ long branches allow them to capture antigens and convert them from proteins into peptides; they then present these peptides to T-cells3.
There are several types of DCs that can act as antigen presenting cells (APCs) for T-cells. One specific subset of DCs from inflammatory monocytes was long thought to be critical APCs4. However, new research from an international team of researchers, led by Dr. Bosteels at the VIB-UGent Center for Inflammation Research, finds that these DCs are actually not APCs at all5. Until now, monocyte-derived DCs were actually mistaken with a similar-looking DC called inflammatory type 2 conventional DC (inf-cDC2). The team used single-cell technologies to study mice with viral respiratory infections (influenza and pneumonia). These techniques, including fluorescence microscopy, allowed them to finely separate monocyte-derived DCs from inf-cDC2s. They found that the inf-cDC2s are able to produce the strongest immune response by combining characteristics from other APCs, like monocytes, macrophages, and conventional DCs5.
This study is especially relevant in the midst of the COVID-19 pandemic, which is also viral respiratory infection. The team found that inf-cDC2s have receptors for the antibodies found in the blood plasma of patients who recovered from coronavirus, meaning that the antibodies worked at least partially by activating these powerful DCs5. This gives researchers new insight into the mechanisms by which coronavirus-specific antigens are able to fight COVID-19 and could possibly lead to new treatments4. This finding will undoubtedly shape the future of immunologic research. With it, scholars and physicians have not only a better understanding of the body’s immune system but also a new target for treatment of diseases.
 Aristizábal, B., & González, Á. (2013). Innate immune system. In Autoimmunity: From Bench to Bedside [Internet]: Chapter 2. Colombia: Bogota (Colombia): El Rosario University Press. Available from: https://www.ncbi.nlm.nih.gov/books/NBK459455/
 Alberts B, Johnson A, Lewis J, et al. (2002). Molecular Biology of the Cell. In The Adaptive Immune System: Chapter 24. 4th edition. New York: Garland Science. Available from: https://www.ncbi.nlm.nih.gov/books/NBK21070/
 Roghanian, A. (n.d.). Dendritic Cells. Bite Sized Immunology. Retrieved from https://www.immunology.org/public-information/bitesized-immunology/cells/dendritic-cells
 VIB (the Flanders Institute for Biotechnology). (2020, May 8). Newly discovered cell type plays crucial role in immune response to respiratory infections. ScienceDaily. Retrieved May 10, 2020 fromwww.sciencedaily.com/releases/2020/05/200508155915.htm
 Bosteels, Neyt, et al. (2020). Inflammatory Type 2 cDCsAcquire Features of cDC1s and Macrophages to Orchestrate Immunity to Respiratory Virus Infection. Immunity, 2020.