At the NIHR Guy’s and St Thomas’ BRC, we regularly host work experience students to help inspire the next generation of biomedical and clinical researchers. One of our students, Holly Armstrong, told us about her week in the department, and her favourite piece of science from the week – flow cytometry.

My name is Holly Armstrong I am in year 12 at Teddington Sixth Form. I have aspired to be a researcher for as long as I have known. During this week I have had the privilege to spend time shadowing the researchers at Guy’s Hospital. The experience I have been given has exceeded my expectations.

Throughout the week I have seen many different fields of work at Guy’s Hospital, all with one common link, research. I began my week in the Stem Cell Hotel, and then ended up on the Clinical Research Facility (CRF) near to the end.

My favourite aspect of research of the week was flow cytometry and cell sorting, which are present in nearly all of the cell research here. I never thought that flow cytometry and cell sorting could be so fascinating and cool.

I spent time in the Flow Cytometry Platform, where Dr Richard Ellis explained about the work there. I began with zero knowledge about flow cytometry, and ended the day with real excitement about the work.

Firstly, you may be wondering, what is flow cytometry and cell sorting? Flow cytometry is the technology used to measure cells in all kinds of ways, whether it be the number of cells, the type of cells or even the physical and chemical properties of cells. Cell sorting is exactly ‘what it says on the tin’. It involves using a cell sorting machine to separate the cells you want to study from a sample which might have a mixture of different types of cells.

There are many types of flow cytometry, but I really enjoyed learning about fluorescent flow cytometry.

Flow cytometry starts with a sample or cells which can be taken from anywhere in the body. Let’s say the cells are white blood cells. There are many different types of white blood cells, neutrophils, macrophages, lymphocytes, phagocytes.

Researchers then buy some antibodies. On each antibody is a fluorochrome – a tag that emits a fluorescent light. These come in handy later on in the process. The researchers ‘fix’ the cells (preserve the cells so they’re not living) and then mix the cells with the antibodies. There are different antibodies that bind to different receptors on different cells. They tag the cells so they can be distinguished.

In the flow cytometer, the mixture of cells with the antibodies attached to them, are put into a tube under high pressure so all the cells are in single file.

A laser beam goes across the tube where the cells are going in single file. When the cell hits the laser, the fluorochrome on the antibody gets excited and starts emitting a specific colour of light, depending what type of flourochrome it is.

Now you can detect how many events of each colour there were and therefore, how many of that type of cell.

It’s an amazing process that can be used for many different things, including immunophenotyping (analysis of heterogeneous populations of cells) and even in diagnosis of some types of cancer including leukaemia and lymphoma, HIV.

I would say that flow cytometry is my favourite aspect of the research I learn this week, because it is very important in all cell biology research, and is really under representated to the public.

Overall, I really enjoyed my week here at Guy’s and St Thomas’, and give my upmost thanks to Ania Rainbird, Anna Perman, and Maria Thomas for organising and taking care of me this week and to all the researchers who I shadowed and all the wonderful staff who took me on countless tours and gave me great knowledge and advice. Thank you, I have never felt more welcome.