Human Leukocyte Antigen System

Telling health from harm

The human immune system is designed to protect the body from disease, without damaging healthy cells.

To do this, it relies on a method for being able to differentiate between cells that are healthy and those that are unhealthy or contain foreign invaders.

The way our immune defense is able to make this distinction is via the human leukocyte antigen (HLA) system.1

The role of HLA in the immune system

The human leukocyte antigen system works by displaying certain markers – called peptides – on the surface of a cell. These markers tell the immune system what is happening inside the cell, for example whether or not the cell is infected.1

Our T cells – a key type of white blood cell – can recognize these markers through their T cell receptor (TCR). If an abnormal marker is detected, the T cell activates and attempts to kill the cell.  

This remarkable mechanism allows the body to identify and mount a defense against infectious diseases and cancer, but it can also cause autoimmune diseases, in which the body attacks itself.

Why HLA matters in immunotherapy

Sometimes, our body’s T cells overlook abnormal markers presented by the HLA system, or bind to them too weakly. T cells can also become exhausted from a sustained immune response, meaning they do not fight off unhealthy cells as effectively. These issues can contribute to cancer or chronic infections.

In other cases, T cells wrongly recognize a marker as foreign and attack an otherwise healthy cell, causing autoimmune conditions.  

Modern immunotherapy approaches allow us to tune parts of a T cell, specifically its T cell receptor, to increase its capacity to recognize markers presented by the HLA system, bind to them and destroy the unhealthy cell.  

It is also possible to engineer potential therapies that can help stop the immune system attacking healthy cells, by switching off rogue T cells that have wrongly identified markers as abnormal.

By leveraging the HLA system, and its interaction with T cells, we can develop new immunotherapies that optimize the power of the body's own immune defenses.

HLA and ImmTAX technology

Much like the natural immune system, our ImmTAX technology is designed to recognize HLA markers and then send a signal to the body’s T cells to either activate them or turn them off.

An ImmTAX molecule does this by binding to the cell it wants to kill or protect – via the HLA system – and forming a bridge to the body’s T cells.

In cancer and infectious diseases, this bypasses the need for the person’s T cells to locate the unhealthy or infected cell on their own.2,3 In autoimmune diseases, it allows an inhibitory signal to be sent to T cells to stop them from wrongly attacking an otherwise healthy cell.4

Because the HLA system presents peptides from the vast majority (approximately 90%) of proteins made by the human body, ImmTAX molecules have the potential to fight a wide range of conditions, from cancers to infectious diseases and chronic autoimmune conditions.5

You can find out more about what an ImmTAX molecule is made up of here.

ImmTAX technology also has the potential to harness other methods the immune system has for distinguishing healthy cells from unhealthy cells, such as the cluster of differentiation (CD) protocol.

A note on HLA types

Although everyone’s HLA system does the same job, its genetic coding varies between individuals, similar to a blood type. Eligibility for certain forms of immunotherapy, including ImmTAX molecules, depends on a person’s HLA variant, known as an allele.  

A simple blood test can be performed to identify a person’s HLA status.

[1] Medhasi S, et al. J Immuno Res 2022; https://doi.org/10.1155/2022/9710376.
[2] Dolgin E. Nature Biotechnology. 2022;40(4):441-4
[3] Liddy N, et al. Nature Medicine. 2012;18(6):980-7.
[4] Curnock AP, et al. JCI Insight. 2021;6(20).
[5] Damato BE, et al. Cancers (Basel). 2019;11(7):971.

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DOP: October 2025