SigA is the first line of defence when the body comes into contact with the outside world. It is secreted in the lungs, genital system, saliva and gut to deal with bacteria, viruses and other micro-organisms that cause diseases such as pneumonia and diarrhoea.

The antibody is so big, complex and fragile that it has proved extremely difficult to crystallise and despite its importance and prevalence – no new information on SIgA's structure has been available since the early 1970s.

UCL's Structural Immunology group recently mapped data from neutrons at ISIS and X-rays at the European Synchrotron Radiation Facility onto each other in order to uncover SIgA's molecular structure [Bonner et al., Mucosal Immunology, (2009) 2(1):74].

These results provide more information about how the antibody is secreted from inside the body to outside and how the structure of these antibodies affects how they work. With this information scientists can begin to replicate them.

“In the very young, the elderly and others whose immune system is less efficient, the ability to make efficient vaccines or artificial versions of these antibodies could be increasingly important for public health, particularly with the possible spread of new organisms,” says group leader Professor Steve Perkins from UCL.