Strikingly, the proximity of MCs and IgE+ TLOs at site of tissue injury in the wall of progressive aneurysms supports a possible role for these highly reactive inflammatory cells in the progression of the disease and in the maintenance of the pathologic loop, through their production of IL-4 in response to locally produced IgEs, which in turn sustains the IgE+ germinal centre cells in local TLOs. This evidence concerns the gene IL4 and aneurysm.