Too Much Of A Good Thing

December 05, 1997

The type of antibody responsible for hayfever may play a deadly role in malaria. At the British Society for Immunology Annual Congress in Brighton this week Dr Marita Troye-Blomberg of Stockholm University, Sweden will explain why she thinks that IgE could be a killer.

At any time an estimated 300-500 million people are infected with malaria and 1.5-3 million, mostly children, die each year. The form of malaria which most often results in death is cerebral malaria, in which blood clots form in the brain. Patients with cerebral malaria have higher levels of IgE type antibodies in their blood than people with milder forms of the disease.

Although not formally proven in the human malaria parasite, P. falciparum, it has been firmly established that IgE is produced in response to the mouse parasite P. chabaudi. The Swedish researchers have shown that in the human disease IgE antibodies cause cells of the immune system to produce a messenger molecule called tumour necrosis factor (TNF).

TNF has many beneficial effects in the body's fight against the malaria parasite: for example it causes fever which reduces the rate at which the parasites grow and sets off pathways by which parasite-infected cells are killed. However, it is also known that individuals who produce excessive amounts of TNF have an increased risk of dying from cerebral malaria.

Dr Troye-Blomberg has looked at results from twins with malaria. Identical twins produce very similar amounts of IgE whereas non-identical twins do not, suggesting that the amount of IgE produced by an individual is genetically controlled. There also seems to be a genetic link to the amount of TNF an individual produces in response to IgE.

Therefore, Dr Troye-Blomberg and colleagues suggest, those people who produce excessive amounts of IgE and TNF will be at high risk of developing severe malaria infections.

Clearly both IgE and TNF are vital to help the body fight parasitic infections. However, they have powerful effects which must be carefully controlled. Dr Troye-Blomberg issues a warning to those developing vaccines and other immunoregulatory drugs against malaria: "our data provide evidence that immune responses aimed at protection may easily become harmful to the host if not properly controlled."

Learning how to damp down the effects of the body's own defence mechanisms could help to improve the outlook for children with malaria.

Notes:
1. Dr Troye-Blomberg is speaking in the Intracellular Infections session on Friday 4 December. The BSI 5th Annual Congress will be held at the Brighton Centre, Brighton, UK from 2-5 December 1997.

2. Dr Marita Troye-Blomberg can be contacted at Stockholm University, Dept. of Immunology, S-106 91 Stockholm, Sweden. Tel. +46-8 164170 Fax. +46-8 157356 marita@imm2.su.se

3. There will be a press office at the meeting from 9am on Tuesday 2 October. Tel: +44 1 273 724 320 / 0378 406 416. Journalists are welcome to attend but are asked to contact Kirstie Urquhart before hand to register.

4. Before the meeting Kirstie can be contacted on +44 181 875 2402 / kirstie@immunology.org

British Society For Immunology

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