Antibodies are proteins produced by the immune system as part of the protective response to foreign objects, such as bacteria and viruses. Sometimes, a person will develop antibodies against the drugs they are taking. This can reduce or neutralise the drug's effectiveness as their body tries to remove the drug.
People with MS can develop neutralising antibodies to some disease modifying drugs. Treatment with one of the beta interferon drugs (Avonex, Betaferon, Extavia and Rebif), or Tysabri (natalizumab) 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.
If you are taking one of these drugs, you may be given the opportunity for a blood test from time to time, to check for the presence of neutralising antibodies. If high levels of antibodies are found, your neurologist may discuss whether you wish to continue with treatment or to switch to a different disease modifying drug.
If you have antibodies against one of the beta interferon drugs, they will react with all the other beta interferons.
People taking Lemtrada (alemtuzumab) can also develop neutralising antibodies. Lemtrada is delivered through infusions, and the presence of antibodies means that later infusion cycles may be less effective. Your neurologist may wish to monitor you to check.
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.