The lung transplant is an immunocompetent organ, it induces anomalies of the means of defence and a powerful immunological disturbance. After transplantation a depression of the means of defence is seen, in particular non-immunological with a diminution in certain macrophage functions and the maintenance of a local alloreactive phenomenon. During an acute rejection, the graft is the centre of an accumulation of effector cells of the allograft reaction. The syndrome of bronchiolitis obliterans, associates the presence of these same cells to the increase of immunogenicity of the lung transplant. During infections the observed anomalies are similar to those seen during a rejection, further more a link exists between the pathophysiology of infection and rejection. Overall, lung transplantation induces an immunological deficit as is evident by the frequent increase of rejections and infections.