CCL21 and idiopathic pulmonary fibrosis: Further, CCL21 has been implicated in the formation of secondary (i.e., lymph nodes) and tertiary (i.e., bronchoalveolar lymphoid tissues) lymphoid tissues, with the latter being observed in IPF lung biopsies (Campbell et al., 1985; Wallace et al., 1996; Marchal-Somme et al., 2006; Rangel-Moreno et al., 2006).