A cure for rheumatoid arthritis is a step nearer after scientists found an antibody which treats the cause of the pain rather than just the symptoms.
In a finding which offers hope to millions in severe pain, tests have shown that anti-CD4 antibodies attack the white blood cells that cause the debilitating disease without affecting other cells.
Researchers from the University of Lisbon in Portugal say the discovery is an improvement on existing treatments which do not target the source of pain, but merely mask its symptoms.
Breakthrough: Scientists have discovered an antibody which treats the cause of arthritis pain
Tests in mice with arthritis have already shown positive results and there are plans to develop a drug for humans according to the journal PLoS.
Currently there is no cure for rheumatoid arthritis which affects more than 60million, or 1 per cent of the world's population.
Dr Luis Graca said: 'The new treatment is remarkable because it specifically stops the abnormal immunological response behind RA without touching the rest of the immune system, and a short treatment has long-lasting effects suggesting that it might even cure the disease.
'In contrast, all therapies available for arthritis work by shutting down large parts of the immune system - compromising the patients' capacity to fight other diseases.'
In the latest study, Dr Graca and colleagues found that an antibody being used to help transplant patients accept new organs had a benefit for arthritis.
The antibody reacts exactly on the subsets of white blood cells - the CD4 cells which are at the core of the immune response in arthritis.
The researchers also used a recently-discovered breed of mice called SGK that suffers from chronic arthritis like humans, which they have based their tests on.
Dr Graca said: 'SGK mice treated with the anti-CD4 antibodies at the same time that arthritis was induced showed no symptoms of disease.
'In contrast, control mice, injected with an irrelevant antibody, suffer full-blown arthritis.
'Even more interesting, the protection is still active long after the antibody had disappeared from the animals' system showing a lasting effect that suggests the antibody is not just suppressing the auto-aggressive response but had, somehow, switched it off.
'We know humans also have cells involved in protection against autoimmunity. These are both good signs for success in humans.'