vIL-6tg2 mice exhibit increased splenic extramedullary hematopoiesis and plasmacytosis, and increased cell proliferation in lymph nodes and spleen. (A) Representative hematoxylin and eosin-stained sections of spleen from 21-week-old wt (Ai) and vIL-6tg2 (Aii) mice, showing an increased number of megakaryocytes and granulocytes in vIL-6tg2 only (20-fold magnification). (Aiii-iv) Giemsa staining of serial sections from the same spleen shown in subpanels i and ii at 40-fold magnification. vIL-6tg2 display a cluster of mature plasma cells (encircled) and several foci of erythropoiesis as marked by arrows (iv) that are not observed in wt (iii). (B) Ki67 staining of PLNs (Bi-ii) and spleen (Biii-iv) of a 15-week-old wild-type (i,iii) and vIL-6tg2 (ii,iv; 10-fold magnifications). Increased proliferation was observed in hyperplastic germinal centers of lymph nodes from transgenic mice (ii). vIL-6tg2 spleen tissue (iv) showed increased proliferation in the red pulp of vIL-6tg2 spleen, indicating hematopoiesis. Representative images are shown.
