Expression of secreted osteoclastogenic factor of activated T cells (SOFAT) by T- and B-lineage cells may contribute significantly to bone loss in periodontitis. (CCR3P.221)

Abstract

Abstract A novel T cell-secreted cytokine, termed secreted osteoclastogenic factor of activated T cells (SOFAT), that induces osteoclastic bone resorption in a RANKL-independent manner, has recently been described. We have previously reported that SOFAT is highly expressed in gingival tissues of patients with chronic periodontitis (CP) suggesting a putative role in the bone loss associated with CP. Here we characterized the cell types producing SOFAT in CP. Gingival tissues were biopsied from subjects without periodontal disease (n=5) and patients with CP (n=5) and SOFAT quantified by immunohistochemistry and immunofluorescence staining. Our data reveal marked SOFAT staining in CP that was predominantly associated with the lymphocytic infiltration of gingival tissues. Interestingly, besides CD3+ T cells, B-lineage cells including plasma cells also exhibited strong staining for SOFAT. Because SOFAT has not previously been reported in B-linage cells, we further purified splenic T cells and B cells from Balb/c mice and activated them using LPS or CD3/CD28 antibodies respectively. SOFAT was quantified by RT-qPCR and revealed significant induction of SOFAT expression in both activated T cells and B cells in comparison to unstimulated cells. Our data support a putative role of SOFAT in the bone loss associated with chronic periodontitis and further demonstrates for the first time that in addition to T cells, B-linage cells may also be a significant source of SOFAT in inflammatory states.