ID1 and melanoma: In contrast to the results obtained with WT cells, we detected a significant increase in Id1−/− DC numbers when BM progenitors were cultured in the presence of B16F10 melanoma TCM (1.4-fold; Fig. 2e) and no significant difference in MDSC numbers compared with controlled media cultures of Id1−/− cells, indicating that Id1 has a causal role in the myeloid differentiation impairment observed in the presence of tumour-derived factors both in vitro and in vivo.