GRAMD1B and Legionnaires' disease: Among the 60 Legionella species, L. pneumophila and L. steigerwaltii are the only two Legionella species to harbor lamB. Since L. pneumophila is responsible for 85% of Legionnaire’s disease cases, we decided to determine the role of LamB in the intracellular infection of amoebae and human macrophages2,59.