Figure 3.

Serial changes in B7-1 and B7-2 expression within murine cardiac allografts. BALB/c hearts transplanted into C57BL/6 recipients were harvested after 1 or 3 days and sections stained for the expression of CD80 (B7-1) or CD86 (B7-2). Day 0 panels represent a harvested donor heart immediately before transplantation. An isograft control (BALB/c donor into BALB/c recipient) was harvested on day 1. Arrowheads in a and c indicate the weak labeling for B7-1 that is restricted to interstitial dendritic cells in the first day posttransplantation, whereas by day 3, dense mononuclear and some capillary endothelial cell labeling is seen (g). In contrast, B7-2 is expressed by occasional graft endothelial cells (arrowheads in b) but is rapidly and densely up-regulated in allografts within 24 hr (d) but not in a day 1 isograft (f). Where indicated, the recipients were treated with DST plus 200 μg of anti-CD40L mAb at the time of transplantation (i and j). DST plus CD40L mAb administration blocked up-regulation of B7-1, without affecting graft cellularity (compare g and i). The dense endothelial expression of B7-2 was not modulated by DST plus anti-CD40L mAb (compare h and j). DST plus control Ig did not affect the marked increase in intragraft B7-1 seen at day 3 in control allografts (data not shown). Cryostat sections, hematoxylin counterstain. (Bar = 50 microns.)