Fig. 4. Expression of host cell genes involved in the regulation of apoptosis in response to T. gondii infection. (A) Wild-type (WT) and p65^–/– MEFs were infected with T. gondii for 20 hours and total RNA was isolated as described in the Materials and Methods section. Radiolabeled cDNA probes were hybridized to nylon membranes of the Mouse Apoptosis GEArray Q Series, which consist of a panel of 96 genes associated with apoptosis and four housekeeping genes (Superarray). Signals corresponding to the cDNAs hybridized to each gene were detected by phosphorimaging. Integrated densitometric values were calculated from each spot and normalized to actin values. On the y axis, ratios between infected and mock-infected values for each gene were calculated to depict changes in gene expression after infection. Bars represent the means of three experiments corresponding to the 100 genes in the array, which were grouped into families on the x axis. The identity of the complete set of genes and the levels of expression as a result of infection are shown in Table 1. A comparative analysis of wild-type and p65^–/– MEFs revealed distinct patterns of gene expression in response to T. gondii infection. (B) Expression of apoptosis-related genes belonging to the Bcl-2 and IAP families. Differences between WT (black bars) and p65^–/– (white bars) infected MEFs were most evident in the expression of the Bcl-2 anti-apoptotic gene Bfl-1 (top) and the IAP members NAIP1 and IAP2 (bottom). Levels of expression of Bcl-2 proapoptotic genes were similar in both cell lines (middle). Bars denote ratios between infected and mock-infected gene expression levels and represent the means ± standard deviations of three separate experiments.