Flow Cytometry Cross-matching (FCXM)

Flow cytometry can be used to analyze different cell types. This technique can be applied to immunology to ensure that, prior to a transplant procedure, interactions between donor and recipient immune components do not cause an adverse immune reaction.

Flow cytometry can be used to cross-match human leukocyte antigens on the surface of APCs before a transplantsciencepics | Shutterstock

The role of HLA proteins

The human leukocyte antigen (HLA) proteins are crucial for the body’s immune defense against potentially harmful foreign substances. Class I and II HLA (HLA I and II) proteins are the ones involved with the immune response and transplantations. HLA I proteins are expressed on the surface of all cells. Conversely, HLA II proteins are expressed on the surface of antigen presenting cells (APCs) of the immune system, such as Dendritic cells and B-Cells.

Antigens and proteins are broken down into peptides, and these peptides form a complex with HLA proteins. The HLA-peptide complex subsequently interacts with effector T-cells causing intracellular signals in both cells, which determines if a specific immune response occurs. Effector T cells differentiate between ‘self’ and ‘non-self’ proteins - therefore, if the peptides presented are recognized as ‘non-self’, an immune response will commence.

HLA proteins are highly varied, as three genes contribute to the formation of HLA I proteins, while six genes contribute to the formation of HLA II proteins. Given that there are two distinct alleles for each gene, the possible combinations are numerous.

Flow cytometry

Flow cytometry represents an analysis technique that can be used to study both the physical and chemical properties of cells and/or particles. During flow cytometry, the sample is suspended in a fluid and injected into the flow cytometer. Usually, one cell at a time is passed through a laser beam for analysis purposes. The scattering of light caused by this gives information on the characteristics of the cells of the sample.

The cells are fluorescently labeled before being passed through the cytometer. The labels contain antibodies which are attached to fluorochromes. Separate labels can be used for different cells within a sample, which allows for a heterogeneous population to be analyzed. Isotopes can also be attached to the antibodies, which is usually seen during mass cytometry.

Flow cytometry cross-matching

Flow cytometry cross-matching (FCXM) involves mixing donor lymphocytes, the recipient’s immune serum, and fluorescent labeled antibodies into a sample. The antibodies used are specific to the donor HLA and various T-cell and B-cell specific markers (e.g. CD3, 5, and 8 for T-cells, and CD19, 20, and 21 for B-cells).

The sample is the ran through a cytometer, so the lymphocytes can interact with the antibodies in the recipient’s serum. If there are donor-specific HLA antibodies in the serum, they will bind to the donor lymphocytes, which allows the fluorescently labeled antibodies to bind, giving in turn a positive cross-match.

The benefits of flow cytometry cross-matching before transplantation

A problem with allograft transplants is that organ rejection can occur, which is seen as a result of the recipient’s antibodies against the donor HLA. This will elicit an immune response which can subsequently cause rejection.

Since a positive FCXM is associated with an increased chance for a transplant recipient to reject the prospective transplant, FCXM is important, as it allows for donor antigens and host antibodies to be checked prior to a transplant to avoid a host immune response. This reduces the chances of acute or chronic allograft rejection.

Complications with flow cytometry cross-matching

During flow cytometry, the antibodies that are used can bind non-specifically and give unreliable results. This can be caused by protein-protein interactions, glycolipid interactions, electrostatic interactions, and binding to Fc receptors.

The use of a pre-digestion agent can reduce the chances of non-specific binding, which increases the sensitivity and reliability of the analysis. Finally, combining other analytic techniques (such as sera absorption) with FXCM can also reduce the rate of false-negative results.

Further Reading

Last Updated: Jun 25, 2019

Written by

Samuel Mckenzie

Sam graduated from the University of Manchester with a B.Sc. (Hons) in Biomedical Sciences. He has experience in a wide range of life science topics, including; Biochemistry, Molecular Biology, Anatomy and Physiology, Developmental Biology, Cell Biology, Immunology, Neurology  and  Genetics.

Citations

Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Mckenzie, Samuel. (2019, June 25). Flow Cytometry Cross-matching (FCXM). News-Medical. Retrieved on December 06, 2024 from https://www.news-medical.net/life-sciences/Flow-Cytometry-Cross-matching-(FCXM).aspx.

  • MLA

    Mckenzie, Samuel. "Flow Cytometry Cross-matching (FCXM)". News-Medical. 06 December 2024. <https://www.news-medical.net/life-sciences/Flow-Cytometry-Cross-matching-(FCXM).aspx>.

  • Chicago

    Mckenzie, Samuel. "Flow Cytometry Cross-matching (FCXM)". News-Medical. https://www.news-medical.net/life-sciences/Flow-Cytometry-Cross-matching-(FCXM).aspx. (accessed December 06, 2024).

  • Harvard

    Mckenzie, Samuel. 2019. Flow Cytometry Cross-matching (FCXM). News-Medical, viewed 06 December 2024, https://www.news-medical.net/life-sciences/Flow-Cytometry-Cross-matching-(FCXM).aspx.

Comments

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
Post a new comment
Post

While we only use edited and approved content for Azthena answers, it may on occasions provide incorrect responses. Please confirm any data provided with the related suppliers or authors. We do not provide medical advice, if you search for medical information you must always consult a medical professional before acting on any information provided.

Your questions, but not your email details will be shared with OpenAI and retained for 30 days in accordance with their privacy principles.

Please do not ask questions that use sensitive or confidential information.

Read the full Terms & Conditions.

You might also like...
Neoantigen DNA vaccines improve survival and immunity in triple-negative breast cancer patients