Fig. 4.

Immunization with donor splenocytes preblocked with B7AP induced prolonged allograft survival. Single cell suspension of donor C57BL/6 spleen cells (5 × 10⁶/50µl) in serum-free RPMI-1640 were irradiated with 30 Gy gamma-ray and precultured with 7·8µm B7AP at 37°C for 90min. These cells were then injected i.v. via the tail vein into 6–8-week-old BALB/c mice: B7AP⁺ (•). The controls were the normal saline group: NS (▪), adriblastine group: Adr (▴), negative control FTD₁₀ group (♦) and untreated C57BL/6 splenocytes: B7AP^– (×). Three days later, neonatal C57BL/6 split-heart cardiac grafts were transplanted into the ear pinna of these preimmunized BALB/c mice. Graft survival was assessed daily by anatomic microscope observation and electrocardiographic monitoring with rejection defined as the absence of a detectable beat.