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Two Clocks Tell T Cells When Their Time’s Up

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An Australian research team has revealed that the immune cells that fight infections in our body are under the control of two internal “clocks”, upending previous theories on how immune responses are regulated.

The team at the Walter and Eliza Hall Institute discovered that during an immune response the clocks allocate a certain amount of time in which the cells can divide, and also prescribe the immune cells’ lifespan. The finding sheds new light on how the body controls immune responses, and explains how cancers such as leukaemia and lymphoma may be caused by errors in this system.

Immune T cells are programmed to recognise different microbes. When this happens during an infection, the responding T cells become activated and increase in number by dividing. Tight controls on how many cells are formed and how long they survive ensure that the infection can be successfully fought and that excess immune cells are cleared so they don’t overwhelm the body.

“We had previously shown the number of cells a ‘parent’ T cell produces is tightly regulated,” said Dr Susanne Heinzel. “The suspicion was the T cell ‘knows’ how many times it can divide.

“We were stunned to find this wasn’t the case. The T cell is given an amount of time in which it can divide, like a clock running,” she said. “Once this time is up, no more divisions can happen.

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The full text of this article can be purchased from Informit.