Abnormalities in mutant MKs. (A) Representative images of MKs (yellow arrows) in H&E-stained sections of mouse femur BM from (Ai) A⁺/A⁺ and (Aii-iv) mutant mice. (B) MK densities quantified from H&E-stained femur BM sections. Results represent mean ± SD. A⁺/A⁺: 54.84 ± 14.02 (n = 6); A^gfpR702C/A⁺: 99.24 ± 16.26 (n = 7); A^D1424N/A⁺: 102.38 ± 22.16 (n = 4); A^D1424N/A^D1424N: and 99.68 ± 24.89 (n = 4). *P = .001 1-way ANOVA compared with A⁺/A⁺. (C) MKs in spleens from A⁺/A⁺ (Ci) and mutant (Cii-iv) mice at 4-6 months of age. Note the increased number of MKs in spleens from the mutant mice. Brown stain indicates VWF; and blue stain, hematoxylin. (D) MK emperipolesis (neutrophil inclusions in MK cells) in A^D1424N/A^D1424N and A^E1841K/A^E1841K mouse femur BM. (Di-ii) One or 2 neutrophils (red arrows) are seen in the MKs in H&E-stained sections. (Diii) EM image of an A^D1424N/A^D1424N MK shows a neutrophil (arrow) inside the cytoplasm of a MK. The MK nucleus is indicated by an arrowhead.