"We found that any two people may share tens of thousands of the exact same T-cell receptor. This is contrary to previous dogma that each person has a distinct set of T-cell receptors with little or no overlap between people," said Dr Harlan Robins, a computational biologist and an assistant member of the Public Health Sciences Division at the Hutchinson Centre.

The findings have diagnostic and therapeutic potential for auto-immune diseases and cancer.

"The strong similarity in the adaptive immune cells between different people suggests that the same disease will induce the same response in different people," Dr Robins said.

"The technology... can readily detect such a response, even if the magnitude of the immune reaction is small."

"Therefore, we potentially could use one or more of these shared T-cell responses as a diagnostic for a particular disease."

For the study, Dr Robins and his colleagues sequenced more than five million T-cell receptor DNA strands from each of seven healthy donors.

After comparing these sequences, they found two primary results.

Firstly, the set of T-cell receptor sequences used by the human immune system is not a random cross section of all the possibilities, but a small subset with consistent properties that the scientists subsequently identified.

"Each person's adaptive immune system is far more alike than expected," said Dr Robins.

Secondly, pair-wise comparisons of the T-cell receptors in the seven donors revealed that that tens of thousands of identical receptors are shared by each pair, even in people of different ethnicities.

"The results of our paper suggest that a specific set of T-cells that we can now detect are likely to play a causative role in the disease," Dr Robins said.

"Further, we can detect this targeted set much earlier than present diagnostics, perhaps saving vital cell function with the preventive administration of currently available therapeutics."

"And because the T-cell clones are causative of the disease, they also double as therapeutic targets."

"In principle, a monoclonal antibody could be developed to target these T-cell clones and prevent the autoimmune attack."

"Effectively, the immune system is an amplifier."

"So a very small tumor has the potential to induce a magnified immune response."

"We are readily able to detect such a response."

"The results of this paper suggest that multiple patients might have a similar response to the same type of tumour."

"Therefore, detection of these similar responses could be an early diagnostic for certain types of cancer."