ACTA1 and systemic sclerosis: To further examine fibrosis in the cGVHD-targeted organs, we performed immunohistochemistry for evaluating the expression of the terminally differentiated fibroblast marker α-smooth muscle actin (α-SMA) [29,30] which is expressed at greater levels in systemic organs in the GVHD mice model for systemic sclerosis [5,31,32].