Effects of prior exposure to the bites of uninfected mosquitoes on a blood stage infection of P. chabaudi (ER) transmitted by infected mosquitoes. a) Experimental procedure for the infection of mice with P. chabaudi (ER) through the bites of infected mosquitoes, after being exposed to four weekly sessions of bites by uninfected mosquitoes. One group of mice was only submitted to infectious mosquito bites. b) Course of infection in mice submitted first to uninfected followed by infected mosquito bites (▲), and infected mosquito bites only (■). The infection was followed for 13 days at which time mice were sacrificed and FACS analysis performed (see Figure 4). c) Length of pre-patent period, and peak parasitaemia of mice submitted to uninfected and infected mosquito bites (□), and infected mosquito bites only (■). The values represent the means and standard errors of the means of at least 3 mice per group.