Abstract
Idiopathic pulmonary fibrosis is the most common of the idiopathic interstitial pneumonias and is typically associated with prominent lymphoid aggregates of CD3+ T cells and CD20+ B cells within the lung tissue that are located near sites of active fibrosis. The presence of lymphoid aggregates outside of primary and secondary lymphoid tissues is a prominent feature of many autoimmune diseases and the presence of lymphoid foci can precede the onset of clinical disease. We have examined the B cell profile of IPF patients and aged matched healthy controls using multicolour flow cytometry and analysed the serum for the presence of B cell cytokines BAFF and April, and CXCL13 a chemokine that promotes B cell migration to lung tissue. In contrast to healthy controls IPF patients show an accumulation of plasma B cells in the peripheral blood and a subset of patients show a rise in CD5+ CD23+ transitional B cells. Immunohistochemical staining of lung tissue from IPF patients revealed synchronous accumulation of CD138+ plasma cells and CD5+ B cells within the lymphoid aggregates of IPF patients. IPF patients showed a trend toward increased serum levels of BAFF, April and CXCL13. The presence of plasma cells and CD5+ B cells in the blood and lung tissue of IPF patients raises the important question as to the role of B cells in IPF disease pathogenesis.