Fig. 1.

The tissue immune profile of the gut is distinct in non-responders to MSC therapy. Immunohistochemistry of gastrointestinal acute graft-versus-host disease (aGvHD) biopsies of responder and non-responder patients to mesenchymal stromal cell (MSC) therapy. Biopsies were taken after allogeneic hematopoietic stem cell transplantation (aHSCT), but prior to MSC infusion. Sections were immunohistochemically stained, with DAB, for antibodies targeted against a CD8, b CD4, c FoxP3, d CD56, e CD68, and f ß-tryptase. Corresponding graphs illustrate quantification of immunohistochemical staining from one high power field at × 40 magnification represented as mean pixel area (total DAB area stained/total image pixel area) with 95% confidence intervals (Additional file 1). Non-responders demonstrated an immune milieu suggestive of acute inflammation, potentially less supportive to MSC responsiveness, with significantly higher levels of staining for CD4+ T cells, CD56+ immunostimulatory cells, and CD68+ phagocytes. Scale bar = 50 μm