Cytokine profiling and more recent T cell immunophenotypic studies have associated reflux oesophagitis with a predominantly T helper type 1 (TH1) type cytokine profile, predominated by IFN-γ and interleukin 2 (IL2) expression, whereas BO displays a humoral-type TH2 profile, associated with immunosuppression (42–45). Here, IL2 is linked to bronchiolitis obliterans syndrome.