The goal of this initiative is to obtain sufficient genomic data and a reference data set from retrospective studies of a large number of stored human DC samples to understand the genetic basis of inter-donor variability in responses to DC maturation stimuli. ‘Illumina’ microarrays rather than the ‘Affymetrix’ platform will be used for the necessary transcriptional profiling and subsequent data analysis. Jointly, P2 and P6 identified a large number of stored samples of DC from melanoma patients (who had been treated in clinical trials of DC-based therapy at the two respective centres) that would be suitable for subsequent analysis. However, it further became clear that there were differences in the techniques that had been used to freeze the samples at different period. This necessitated a pilot experiment to compare and assess the suitability (e.g. RNA stability) of different samples frozen in different ways. First results are available. These revealed that all stored samples could be analysed in detail, and it was further decided to process the samples such that analysis of micro-RNA expression could be undertaken at a later stage. Patient samples have been shipped from the two centres to the Wellcome Trust Centre for Human Genetics and the main ‘reference experiment’ commenced at the beginning of 2009.