Despite the lower percentage parasitaemia observed in the mosquito-initiated infections compared with direct pRBC infection, at day 13 of infection there were similar increases in numbers of splenic cells (Figure 2a) The total number of CD4+ T cells within the spleen increased above control levels by day 28 in the pRBC-infected mice, but not after infection via the mosquito bites (Figure 2b), suggesting that the impact of direct blood challenge brought about greater CD4+ T cell proliferation. This evidence concerns the gene CD4 and infection.