Disruption of GC formation by LTβR-Ig treatment reduces lung dysfunction and cGVHD organ tissue fibrosis. B10.BR recipients were transplanted as per Figure 1. A cohort of animals receiving BM + splenocytes were treated with 200 μg of murine LTβR-Ig or the control Ab, murine MOPC21, every 3 days beginning on day 28 after transplantation until day 52. (A) Spleen tissue harvested from these animals at day 60 was analyzed by immunofluorescence for GC structures. GCs were detected by colocalization of IgM (green), VCAM-1 (blue), and peanut agglutinin (red); merged images show overlap (white) to discriminate GC. White arrows highlight GC. Images were captures with an Olympus FluoView 500 confocal laser scanning microscope at 100× magnification; n = 5. (B) The size of the GC was quantified by measuring the area of peanut agglutinin staining in Photoshop C3. (C) Frequency of GCs was quantified by counting the number of GCs in 1 mm² of spleen section. (D) PFTs were performed on anesthetized animals on day 60 after transplantation to measure lung function. (E) Animals treated with LTβR-Ig and MOPC21 were examined for fibrosis in the lung and liver. (F) Presence of deposited lung and liver tissue–specific antibodies in animals treated with LTβR-Ig and MOPC21 was determined by immunofluorescence by staining with FITC-conjugated anti–mouse Ig. White arrows depict Ig deposition. Images were captured at 200× magnification and are representative of 2 individual experiments; n = 5. *P < .05; **P < .01.