Characterization of two novel markers involved in cross-presentation by dendritic cell subpopulations in tonsillar tissue and monocyte-derived dendritic cells

Abstract

Cross-presentation is an essential mechanism of the immune system when it comes to fighting viruses and tumors. Oropharyngeal cancer (OPC), which can affect tonsillar tissue, is highly associated with high-risk human papillomavirus (HPV) infections and CD8+ T-cells directed towards killing HPV-infected cells could prove to be a promising treatment of HPV-induced OPCs. In this study, the expression levels of two novel markers, marker X and marker Y, previously described to be involved in cross-presentation, were analysed on different dendritic cell (DC) subsets in tonsils and on peripheral blood monocyte-derived dendritic cells (moDCs) and compared with other cell types, in order to determine the relevance of the markers as therapeutic targets for antigen delivery and activation of cross-presentation mechanisms in tonsillar cancer. For tonsillar cells, marker X was confirmed to be highly expressed by at least two subsets of myeloid DCs, as well as at lower levels by macrophages. Marker Y was highly expressed by all subsets of myeloid DCs and macrophages as well as at lower levels by B-cells and plasmacytoid DCs. The results for marker Y are uncertain however, and further tests are required. For moDCs, marker X was present on cells matured through lipopolysaccharide (LPS)-stimulation, although the expression levels were low compared to tonsillar DCs. Furthermore, a set of eighteen marker X-specific single-chain variable fragments were produced and tested for affinity on monocyte-derived Langerhans cells with the scope of designing antibodies against marker X that could be further used to assess the functional role of this marker. The results of that assay require further testing. On this basis, a literature review on the establishment of CD8+ HPV-specific T-cell lines was conducted.

Popular Abstract

The most powerful weapon in the constantly ongoing war against cancer is already here, and it is operating inside of you at this very moment. The only question remaining is how to run it at its full potential. This is the idea behind this study hoping to provide new cancer treatments by giving the immune system a well-earned boost.

Every year, approximately 330,000 people die from cancers in the oral cavity and throat, such as tonsillar cancer, worldwide. A majority of the cases of tonsillar cancer are linked to an ongoing HPV (human papillomavirus) infection. HPV is the most common sexually transmitted disease in many countries, and almost every sexually active person is likely to be infected by it at some point in their life.

The immune system is an amazingly complex machinery tailored to fighting off unwanted intruders, such as viruses like HPV, in the body. It consists of many different types of cells, but one of the immune cell types that interests researchers hoping to improve the immune response towards cancer is so called dendritic cells. Dendritic cells, named for their appearance of having tree-like extensions of branches, are specialised at dealing with the unwanted intruders. When they encounter something suspicious, they begin by “eating” and digesting it before showing off the remains of their prey on their surface. This seemingly morbid process allows for another immune cell type, so called T-cells, to recognise the remains presented by the dendritic cells and become activated. Activated T-cells can evolve into straight out killing machines with only one goal in sight: to destroy the remaining intruders. They do this by creating small holes in virus-infected cells, killing them as their insides leak out.

Scientists are hoping to make this process more efficient by targeting certain proteins on the surface of dendritic cells. Proteins are large molecules involved in almost every imaginable process in your body. The proteins will be targeted with another type of proteins, called antibodies, linked to molecules imitating viruses. The idea is to help dendritic cells do their job, thus streamlining the process of activating killer T-cells. This study has investigated two new proteins on the surface of dendritic cells in tonsils for their potential use as targets to boost dendritic cells. These boosted dendritic cells could then hopefully serve as a new treatment of HPV-induced tonsillar cancer. The focus in this study has been to analyse how common the proteins are on different types of dendritic cells in tonsils. Additionally, the foundations for determining the functions of the proteins have been set.

The technique that was used for analysing the cells in the study is called flow cytometry. A flow cytometer contains a set of lasers that can analyse several thousand cells per second individually. It does this by detecting different colours emitted by antibodies that has been bound to certain proteins on the cell surfaces. By doing this, it is possible to see exactly which proteins that are present on a cell.

The study successfully showed that one of the proteins investigated in this study was present on two types of dendritic cells in tonsils. The other protein was widely present on all types of dendritic cells, as well as on some other cell types. Because of this, it is important for researchers in the future to be careful as targeting this protein might lead to some undesired side-effects if the wrong cell type becomes affected. For one of the proteins, an attempt was also made to produce the firsts part of antibodies with specificity towards it, but sadly, the results were inconclusive, and the experiments need to be performed again.

Before testing new medical treatments on humans, it is important for researchers to have a good model of what the body’s response to the treatment will be. Because of this, the study also analysed the two proteins on a cell type commonly used for modelling dendritic cells in the lab. Unfortunately, the results showed large differences with the actual tonsillar dendritic cells, and future researchers will have to find another way of overcoming this problem.

In conclusion, many of the results from this study need to be verified with further experiments, but the results are still relevant for increasing the understanding of the two proteins and what targeting them in future cancer treatments can mean. A surprising side-discovery of the study, however, was that the most common way of classifying dendritic cells used by scientists today might need to be revamped, as the dendritic cells in this study proved difficult to classify like this.

• author: Andersson, Johan and Weidman, Joel
• supervisor: Malin Lindstedt; Christina Sakellariou
• organization: Department of Immunotechnology
• course: KIMM05 20201
• year: 2020
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 9027582
• date added to LUP: 2020-09-21 16:52:52
• date last changed: 2020-09-21 16:52:52