IL4 and chronic obstructive pulmonary disease: In summary, we report that BAFF expression is increased in the cells of sputum and the plasma from COPD patients and the plasma BAFF levels are inversely correlated with FEV1%pred in COPD; BAFF inhibits the apoptosis of CD8+ cells and increases the expression of perforin and granzyme B in these cells from COPD patients; BAFF increases IFN-γ but not IL-4 expression in the CD4+ cells from COPD patients.