Effects of vIL-6–expressing cells in nude mice. (A) Spleen and liver sizes of mice injected with control or vIL-6 producing clones. Data reflect the mean (±SD) of the weights of spleens and livers (5 mice in each group). Hematoxylin-eosin stained spleens from (B) a control mouse and (C) a mouse injected with vIL-6–expressing cells (original magnification × 40). (D) Immunohistochemical staining for κ light chains of splenic white pulp (original magnification × 1,000) of a mouse injected with vIL-6–expressing cells showing plasmacytosis. Chloroacetate esterase stained sections show (E) expansion of myeloid cells (stained red), erythroid precursors, and megakaryocytes in the red pulp (original magnification × 200) and (F) myeloid cell islands in the liver (original magnification × 400) in a mouse injected with vIL-6–expressing cells. (G) Hematoxylin-eosin–stained lymph node in a mouse injected with vIL-6–expressing cells (original magnification × 800) showing plasmacytosis.