Reduced expression of activin A in focal lymphoid agglomerates within nasal polyps

It has been previously reported that activin A, a homodimer of the PA inhib in subunit, is secreted by stromal cells from mouse bone marrow and causes apoptotic death of mouse plasmacytoma tumor cells. Recent in vitro studies have also implicated this cytokine in the suppression of normal B-cell lymp hopoiesis. In this study we examined the occurrence of activin A in nasal p olyp tissues that present a combination of epithelium, mesenchyme, and vasc ular endothelium, with frequent massive hemopoietic infiltration. Anti-PA-c hain antibodies strongly stained epithelial mucous glands and some endothel ial cells, and diffusely stained the polyp stroma. Normal adult conchae wer e similarly stained, whereas activin A was not detected prenatally by immun ostaining of nasal tissues. Staining specificity was substantiated by ligan d competition assays. Detailed examination of the inflammatory polyp infilt rate showed that activin A staining was reduced in sites of focal infiltrat ion of B-lymphoid cells. It is therefore implied that local accumulation of a large number of B-cells is associated with relatively low activin A expr ession.