About the Authors
Centre for Immunology and Infection, Department of Biology, The University of York, York, United Kingdom
The authors have declared that no competing interests exist.
Conceived and designed the experiments: APM GRJ KGH JDT. Performed the experiments: APM GRJ KGH PCC SA RAP JDT. Analyzed the data: APM JDT KGH GRJ. Contributed reagents/materials/analysis tools: MC. Wrote the paper: JDT APM.