Foxp3 expressing regulatory T cells are found to be protective in AAA formation in mice,[12] while both pro-inflammatory Th1 cells (producing IL-1β, IL-6, TNF-α and IFN-γ) and anti-inflammatory Th2 cells (producing IL-4, IL-5 and IL-10) are linked to the formation of, as well as the protection against AAA[13–19], confirming the highly complex interplay of different immune cells and cytokines in the pathogenesis of AAA. This evidence concerns the gene IL4 and triple-A syndrome.