According to the Lymphoma Association, lymphocytes fight infection as part of the immune system, and they are carried around the body in the lymphatic system. Lymphoma occurs when a lymphocyte goes out of control.

There are two types of lymphocytes: T lymphocytes (T-cells) and B lymphocytes (B-cells). Hodgkin lymphomas develop from abnormal B-cells, while non-Hodgkin lymphomas (NHL) arise from abnormal T-cells or B-cells. All T-cell lymphomas are a type of NHL.

While recent developments, such as immunotherapies, have turned the once fatal diagnosis of B-cell lymphoma into a curable condition, BBC News notes that T-cell lymphoma is much rarer and often more aggressive. T-cell lymphomas account for around one in 10 cases of lymphoma.

However, researchers from Cardiff University, working with biopharmaceutical company Autolus Ltd, have discovered a method of targeting the cancer without destroying the healthy T-cells that are so vital to the immune system.

One of the challenges in treating T-cell lymphomas has been finding a way to eliminate the abnormal T-cells while sparing the healthy ones.

T-cells work by recognising and removing germs via a molecule on their surface, called the T-cell receptor. This is made using one of two duplicated copies of the T-cell receptor gene, called C1 or C2, at random.

This means that the T-cells our bodies use to fight off viruses and other germs will be a near equal mixture of cells using either the C1 or C2 genes. When a T-cell becomes cancerous, the cancer arises from a single cell, so the cancer will be either all C1 or all C2.

The research team discovered a way of eliminating the T-cells based on whether they used the C1 or C2 gene, demonstrating that targeting of C1 T-cells has the potential to kill C1 cancers, leaving all the healthy C2 T-cells unharmed, enabling them to take care of infections.

Professor Andrew Sewell from Cardiff University's School of Medicine explained: "We wouldn't last a week without the essential job our T-cells perform by protecting us from infection. The devastating effects of low numbers of just one type of T-cell are all too evident in HIV/AIDS.

"T-cell lymphomas are particularly difficult to treat without damaging essential, healthy T-cells that are vital to the immune system.

"The new and innovative approach that Autolus have developed now allows potential for removal of all cancer cells without causing any damage to half of our T-cells.

"Since T-cells select use of the C1 or C2 gene at random, this remaining half of T-cells are capable of providing immunity to the pathogens we encounter every day."

Discussing the research, senior science content officer at Cancer Research UK, Dr Justine Alford, said: "This study has demonstrated it's possible to kill cancerous T-cells but, importantly, spare some healthy ones, opening up exciting new treatment possibilities.

"T-cells are a vital part of our immune system and our survival; that's why when a patient has cancer in these cells, it would cause serious harm to use a therapy that targets both healthy T-cells and cancerous ones.

"This research is still in the experimental phase though, so researchers will need to do further studies to prove the method is safe and effective before starting clinical trials in people."

The research, which can be found in the journal Nature Medicine, was funded by charities including Wellcome and Cancer Research UK.