Intriguingly, the mixed WT recipient was frequently closer to the WT➔WT phenotype than the mixed C3−/− recipient: For instance, only in C3−/−➔WT, but not in WT➔C3−/− mice, the amount of chlamydia in the lung was lower than in C3−/−➔C3−/− animals (Figure 4A). This evidence concerns the gene C3 and chlamydia trachomatis infectious disease.