About the cover: Cover is based on an image of a Masson's trichrome-stained lung cryosection from a C57BL/6 mouse administered allogeneic bone marrow and 1 million splenocytes. Coinfusion of low-dose splenocytes with bone marrow transplant results in lung disease with manifestations of bronchiolitis obliterans. For more information, see article by Panoskaltsis-Mortari and colleagues beginning on page 713.