Antibodies are proteins produced by your immune system as part of your protective response to bacteria or viruses. Sometimes, a person will develop antibodies against the drugs they are taking. This can reduce or neutralise the drug's effectiveness.
People with MS can develop neutralising antibodies to some disease modifying drugs (DMD). Treatment with one of the beta interferon drugs (Avonex, Betaferon, Extavia, Plegridy and Rebif), or Tysabri (natalizumab) or Lemtrada (alemtuzumab) can lead to the development of neutralising antibodies.
If you are taking one of these drugs and notice you are having more relapses than you used to, it could be that you have developed neutralising antibodies against it. If you notice any changes, contact your MS team.
You may be given the opportunity for a blood test from time to time, to check for the presence of neutralising antibodies. If the test finds high levels of antibodies, your neurologist may discuss whether you wish to switch to a different DMD.
If you have antibodies against one of the beta interferon drugs, they will react with all the other beta interferons. You may be encouraged to opt for a DMD that works in a different way.
The majority of people will not develop significant levels of neutralising antibodies, and in some people they may reduce again over time. If you are given steroids to treat a relapse, your antibody measurement will not be accurate for at least a month afterwards. You should make sure you tell your MS team about any relapses you have recently had when organising a blood test.