Changes in spleen histology during
infection. 4A-C: Spleens of non-infected control animals, showing well-defined limits between the red and white pulps (A), quiescent T-cell zones without immunoblasts (B); a central arteriole is denoted by an asterisk) and mostly resting B-cell follicles (C). Clusters of weakly stained cells, suggestive of macrophages, were observed (A, C, arrows). D-F: At d7 of infection, haemozoin was observed throughout an engorged red pulp (D, asterisk). Follicles showed numerous phagocytosis centers (D, arrows). Limits between the red and white pulps were blurred and follicles presented light-stained nuclei cells surrounded by small lymphocytes (E), and the B-cell follicles showed penetration by RBCs (E, asterisks). Large cells with weakly stained nuclei suggestive of centroblasts were widespread (central darker area of the image), and mitosis (black arrows) and apoptosis foci (red arrows) were abundant (F). All sections were stained with Lennert’s Giemsa.