Histology of the spleen in TTP/TNFR-deficient mice.

The figure shows hematoxylin-eosin–stained sections of spleen at × 250 magnification. In the TNFR1/2KO mice, the cellularity of the spleen is essentially identical to that of WT mice. The prominent cell type is lymphoid, but the occasional mature granulocyte is present (arrowhead). However, in the remaining panels from TTP-deficient mice (3KO, TTP/TNFR1KO, and TTP/TNFR2KO), myeloid cells at different stages of differentiation have largely replaced the lymphoid cells (arrowheads, mature granulocytes; arrows, immature myeloid precursors). Note also the presence of increased numbers of megakaryocytes (asterisk), a phenomenon also observed in spleens from the TTPKO mice.