The M5/49.4.1 monoclonal antibody reacts with mouse Thy1 also known as CD90. Thy1 is a 25-35 kDa GPI-anchored protein belonging to the Ig superfamily that is expressed by thymocytes, peripheral T cells, myoblasts, epidermal cells, and keratinocytes. The function of Thy1 has not been fully elucidated but is thought to play roles in regulation of cell adhesion, apoptosis, metastasis, inflammation, and fibrosis. This antibody is particularly useful for depletion of T lymphocytes.