The virulence of Aggregatibacter (Actinobacillus) actinomycetemcomitans (localised aggressive periodontitis in humans), Mannheimia haemolytica (pneumonia in cattle), and pathogenic strains of Escherichia coli (extraintestinal infections) has been associated with a ligand/receptor interaction between their respective RTX toxin (LtxA, LktA, and HlyA) and the CD11a/CD18 receptor resulting in leukocytes alterations [23-26]. Here, ITGAL is linked to susceptibility to pneumonia measurement.