Parasitaemia and/or host cell availability influence differential gene expression of Plasmodium yoelii 17X parasites. Groups of wild-type animals (n=5-10) were infected with P. yoelii 17X iRBCs and parasite RNA was isolated on day 10, day 14 or day 18 post-infection. Immunologically intact (WT) and B-cell deficient JHD animals were similarly infected and parasite RNA was isolated on day 10. A third set of mice was immunized three times with a preparation of P. yoelii reticulocyte membrane proteins ( Py RMP) plus QuilA as adjuvant (RMP) or with Quil A alone (QA) prior to P. yoelii challenge. Parasite RNA was isolated on day 10 (QA) or day 12 (RMP) post-infection. The number of genes up- or down-regulated for a given comparison and category is listed as described in Figure1.