Histology of WT hearts transplanted into PKM-immunized control mice and into tolerized mice.

Histology of WT hearts transplanted into PKM-immunized control mice, which were rejected after 30 minutes (A,C), or into tolerized mice and then removed 2 months after transplantation (B,D). Immunostaining of transplanted WT hearts with anti-IgM antibodies (C-D). (A) Hematoxylin-eosin (H&E) staining of WT heart undergoing hyperacute rejection in a PKM-immunized control mouse. Note the blood clot within the artery and the edema among the myocytes. (B) H&E staining of WT heart in a tolerized mouse. The tissue displays no abnormal features. The small spaces within and between the myocytes are an artifact of the staining procedure. (C) Immunostaining with anti-IgM antibodies, demonstrating IgM deposits (counterstaining with hematoxylin) in the WT heart undergoing rejection as in panel A. Similar deposits were observed in sections stained with antibodies to IgG, C3, and C5, using the corresponding antibodies. (D) Immunostaining for IgM deposits in WT heart transplanted into a tolerized mouse as in panel B. Note that no deposits of IgM are observed. Similarly, no distinct deposits of IgG, C3, or C5 were detected (not shown). Sections are from a representative mouse, out of 3 in each group. Original magnification, × 200.