It is becoming increasingly evident that fibroblasts, the key effector cells in scleroderma, are not all the same.  While it has long been recognized that scleroderma fibroblasts are different from those from healthy individuals, it has only been with the advent of new technology and rigorous methodology that basic biology has now shown that there are many subsets of fibroblasts and that they are distinct not only in their cell surface markers, but also likely in their function.  Thy-1 is a well known marker of fibroblasts which has recently been shown to be one of the key subset markers distinguishing one type of fibroblast from another.  We are now using mice and cell lines with alterations in CD90 to explore its role in cutaneous fibrosis as well as to begin defining functionally distinct fibroblast subsets that may be relevant to the pathophysiology of scleroderma skin fibrosis.