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Clara Cells and Injury Post Lung Transplantation: An Evolving Story

We read with interest the recently published report fromKelly et al. in the journal (1). They found that BronchiolitisObliterans Syndrome (BOS) post lung transplantation wasassociatedwithbothadecreaseinthenumberofClaracellsecretoryprotein (CCSP)positive cells in the small airwaysand in CCSP protein levels present in the bronchoalveolarlavage (BAL) at the time of BOS diagnosis. These ﬁnd-ings conﬁrm our previously published ﬁndings early lastyear in which a longitudinally followed study cohort of 63lung transplant recipients (LTRs) revealed that CCSP celland protein signals were not only reduced at the time ofBOS but that, as a group, LTRs who later developed BOStended to have lower BAL CCSP levels as early as 1 monthposttransplantation (2). In addition, the predictive power ofCCSP signal loss was even stronger when IL-8 levels inthe BAL were used to adjust for the level of inﬂammationpresent at each study time point (the likely importance ofthis was also pointed out by Kelly et al. in their report).Taking our report together with the more recent ﬁndingsof Kelly et al., it is suggested that there may be severalmechanisms at play relating to Clara cell/CCSP signal lossandBOSdevelopmentincludingearlylosspotentiallyasso-ciated with ischemia-reperfusion injury/primary graft dys-function and alloreactivity associated loss at various timepoints throughout the life of the lung allograft. The currentevidence supports the possibility that CCSP-positive cellsin the small airways and secretion of their immunomod-ulatory product CCSP play a crucial role in healing andrepair following lung injury from various causes. In thissetting, any genetic polymorphisms that may more gen-erally inﬂuence potential CCSP levels for any given levelof injury/inﬂammatory in the airway microenvironment islikely to be highly relevant. In our report, we also describeda frequent CCSPpolymorphism in the donor [but not in therecipient] that was associated with lower BAL CCSP levelsand BOS development. We believe that this second set ofdescriptive data reported by Kelly et al. provide conﬁrma-tory evidence of our initial ﬁndings and strongly supportfurther investigative efforts to explore this line of researchinbothLTRandotheracuteandchroniclunginjurysettings.