Background Eosinphil-derived inflamatory mediators including cytolines are considered to be important in the pathogenesis of allergic inflammation. Fibronectin (Fn) has been shown to be a physiogical trigger of autocrine cytokihne production by human eosinophils. Fn is encoded by a single gene, but alternate splicing of the primary RNA transcript results in polypeptide diversity in a cell type-specific fashion. Thus, tissue Fn contains approxmately 50% more of the CS-1 cell binding region recognized by the integrin α4 β1 compared with lasma Fn.
Objective Since eosinophil;s are predominantly tissue-dwelling cells we compared the effect of tissue and plasama Fn on eosinophil surivivial in culture.
Methods The viability and vytokine generation of eosinophils (>99.9%) pure) cultured for up to 4 days in 96 well plates coated with tissue Fn. Plasama Fn or BSA was compared.
Results There was a deingficant difference in the ablity if tissue Fn to support eosinophil survival com-pared with plasma Fn (P <0.001). Optimal survivial with tissue Fin was seen at 25 μ. w4ell (70%-+2.0%) viability at 3 days vs 7%-+ 2.2 % viability on BSA). Significant (p <0.001) cell viability on tissue Fn was observed for up to 4 days in culture (54%-+ compared with BSa coated wells. Addition of autologous mononuclear cells (final concentration 0.5%, 1% or 2%) resulted in plasama Fndependent eosinophil surivival comparable to that 99.9% pure eosinophils adhreent to tissue Fn. Tissue Fn-dependent survival was significantly inhibited by anti-interleukin-3, anti-granulocyte macrophage colony stimulating factor (gm-csf) and anti -Il-5 monoclonal antibodies. Picogram quantities of these three cytokins were detected in supernatants from eosinophils cultured for 3 days on tissue Fn was significantly inhibited by anti-31 and α4 β monoclonal antibody (MoAb) and also by MoAB specific for the Cs-1 motif in the IIICS region of fn.
Conclusion These observations show preferential survival of eosinophils cultured on tissue Fn as a result of α4 β-dependent interaction with the CS-1 region of tissue Fn triggering autocrine cytokine synthesis and release,thereby promoting their survival and presistence within the tissues.