On the cover: Marginal zone macrophages form a continuous line of cells adjacent to the marginal zone sinus in the spleen of a young mouse. Immunocytochemical staining of MARCO (brown) reveals the marginal zone macrophages, and MAdCAM-1 (blue) marks the MAdCAM-1⁺ marginal zone sinus lining cells. Original magnification ×25. Birjandi, S. Z., J. A. Ippolito, A. K. Ramadorai, and P. L. Witte. 2011. Alterations in marginal zone macrophages and marginal zone B cells in old mice. J. Immunol. 186: 3441–3451.