The title of the project is ‘identifying the immune cell interactions that cause alopecia areata’. It sounds promising, how much closer will this research bring us to understanding what causes AA? 

Alopecia areata (AA) is an autoimmune condition where the immune system attacks growing hair follicles – the mini-organs of the skin which build and anchor strands of hair. In healthy skin, immune cells are important for protection against infections and have roles in regulating normal processes – including the hair growth cycle!

However, in AA, something goes wrong and immune cells mistakenly start attacking some part of the hair follicles. In other autoimmune conditions like type-1 diabetes and coeliac disease we know exactly what proteins are being targeted by immune cells. But in AA, while we have some ideas, we have not yet identified the target for sure. Importantly, we also do not yet understand why this attack happens in people with AA.

Currently, we know that ‘killer’ CD8 T cells are one of the key immune cells involved in the attack. These cells specifically target and kill hair follicle cells, damaging the hair follicle structure. This damage leads to the initial hair loss in AA and can also make it difficult for the follicle to return to a ‘growth phase’ to regrow lost hair.

Because of this central role for CD8 T cells in AA, often the immunology is framed as just an interaction between these cells and the targeted hair follicle cells.  However, while this highlights one very vital interaction, we also know that CD8 T cells do not work alone. Hair follicles that are under attack during AA are surrounded by many different immune and non-immune cell types. These cells will be interacting with CD8 T cells, hair follicle cells and with each other to influence AA hair loss. By investigating the interactions of these different cell types, we hope to learn more about the mechanisms that contribute to and influence AA hair loss.

You will be using some cutting-edge techniques, does this let us do things that weren’t possible before?

This project will make use of some powerful techniques that will allow us to look at AA immunology in greater detail than previous approaches. We are fortunate to have access to the samples that people have kindly donated (and continue to donate) to the Glasgow Alopecia Areata Research Tissue Biobank. Thanks to their generosity we will be able to use skin and blood samples from people with AA which we can compare to samples from healthy donors.

As mentioned above, we know the immune system is involved in AA and that lots of different immune cells are found around hair follicles in AA skin. Immune cells communicate with each other by releasing chemical messengers known as ‘cytokines’. These messengers bind to structures on the surface of cells known as ‘receptors’. After cytokines attach to their receptors, signals are sent inside the cell to change how it behaves.

It is by targeting this cell communication that JAK inhibitor medicines (like baricitinib and ritlecitinib) work. They prevent immune cells from talking to each other, by blocking signalling of cytokines through their receptors. This targeting of immune cells can be very effective against AA-causing interactions but unfortunately will also affect immune cells that are important for other responses, including those that protect us from infections.

With the techniques we are using in this project, we will be able to look at the immune cells in AA skin in more detail than before, allowing us to identify mechanisms that are more specific to AA, which could provide clues of new targets for future AA treatments.

Mapping the hair follicle environment

One of the techniques we will use is known as ‘spatial transcriptomics’. This can be used to create a map showing where different cell types are located, allowing us to compare AA-affected and healthy skin. It also tells us what genes are activated in those cells, which gives some idea of how the cells are behaving. For example, in the image below, spatial transcriptomics has allowed us to colour code the different cell types found in and around a hair follicle from a person with AA.

Image – Spatial transcriptomic data showing skin and immune cell types found within an AA-affected hair follicle. The image shows the oval-shaped hair follicle in yellow and pink in the middle, with many different types of cells in various colours surrounding it. 

The presence of this huge amount of immune cells around and inside the hair follicle is unique to AA and is not seen in healthy skin samples. This tells us that in AA skin, there are signals drawing the immune cells towards hair follicles. With the spatial technology we will now be able to look in depth at the immune cells found specifically in and around hair follicles and see how these cells behave differently to immune cells found away from follicles and in healthy skin. This will give us insight about the signals and receptors that may be important in attracting immune cells to hair follicles and which ones direct them to cause and maintain hair loss in AA.

Highlighting immune cell interactions

To follow up on the clues from the spatial transcriptomics dataset, we will use a technique known as ‘immunohistochemical staining’. For this technique we attach colourful dyes to specific proteins found on the surface of cells, so that underneath a microscope we can see where different cell types are found in the skin. We will use this technique to label immune cell types of interest, like T cells, as well as to label interesting molecules we identify from the spatial data, like specific signalling receptors. An example of this technique being used to identify T cells in AA skin is shown below.

Image – Immunohistochemical staining of immune cells in AA-affected skin. This image shows individual cells of any type in the skin in blue – the hair follicle structure in this picture has been indicated with a dotted white line. Next to this follicle there is a large cluster of immune cells, which is seen when hair follicles are attacked in AA. By attaching a pink dye to the T cells, we have been able to highlight their position around the hair follicle. The inset in the pink dotted line is a magnification. 

Immunohistochemical staining is much more precise at pinpointing where proteins are in skin tissue, so will be used to confirm whether specific interactions from the previous step (spatial transcriptomics) are found in AA skin. We will perform this staining in healthy skin samples for comparison, so we can understand whether these interactions are specific to AA skin.

Additionally, where interesting molecules are identified in the skin, we plan to test if these are also changed in the blood of people with AA. This will allow us to understand whether the immune cell interactions we have identified may have a wider effect on immune responses around the body. To do this, we will use techniques called ‘flow-cytometry’ or ‘ELISA’, which can identify the levels of specific molecules in the blood. 

What can people expect to hear about this project in the next three years?

Since starting in October, we have hit the ground running with analysis of the transcriptomics data – this has been a steep learning curve but is already shaping up to give us interesting insight on immune cell activity in AA skin. As this project progresses, we plan to share regular updates through the AUK research blog in collaboration with Katie, Joe and Niels. Through these updates we hope to bring people along with us on the journey, keeping you in the loop with how the project is going, what information is emerging with this research and what we hope this work will lead on to.

Ultimately, how do you hope this project will help people with alopecia areata?

Overall, we hope to identify cellular interactions that are important for the activity of immune cells in AA. By identifying such interactions, we aim to improve understanding of the mechanisms that contribute to hair loss in people with AA. Through this insight, we hope our work will support the future development of safer and more effective treatment options for AA, perhaps by targeting the cellular interactions of AA-causing immune cells.

Katie and Joe, you are helping Rona as ‘patient partners’, how do you look at this project?

Katie: “I’m excited to bring my perspective and experiences of AA to the project, and to see the project develop. I feel privileged to be involved at the forefront of AA research.

AA is a disease that is not widely represented outside of the community, and being able to pass new knowledge, both to the alopecia community, and to those less aware of the condition is extremely important.

Though there have been major advancements in the understanding and treatment of the disease; from different types of T-cells, to the JAK inhibitors and the spatial transcriptomics, the disease is far from understood.

I believe that the involvement of myself and Joe is important for both the representation of the community (which I hope to do well), and for the advancement of research, treatment, and our wider understanding of the disease.”

Joe: “I’m very happy to be involved and represent the alopecia community with this exciting project. It’s important to understand the fundamental immunology at the core of AA. While JAKs have shown promise in some cases it’s clear that the causes of AA are a complicated picture. Achieving greater understanding of the roles these cells and molecules play will hopefully then lead to more targeted treatments in the future.

Personally, I find it very encouraging that even at the cutting edge of lab-based research the patient voice is heard. I’m looking forward to following the project with Rona and seeing the outcomes of the research while keeping the alopecia community front and centre of the work.”

We wish Rona the best of luck with the research and look forward to hearing more as the project progresses!