IL4 and leptospirosis: In the second study, Fialho and colleagues reported that alleles from HLA-A (*24 and *31) and HLA-B*08, as well as alleles from the interleukin 4 (IL-4) and IL-4Rα genes were present in significantly higher frequencies in patients with a history of leptospirosis from Terceira Island in the Azores archipelago [6].