Apoptosis and the expression of genes of the Bcl-2 family and TGF-β1 in rat renal allografts transplanted after donor-specific blood transfusion

Factors involved in "operational" tolerance in animal models induced by recipient pre-treatment with donor-specific blood transfusion (DSBT) need elucidation. This study examined apoptosis, expression of genes of the Bcl-2 family and of TGF-β 1 in isografts, rejecting and tolerant allografts. Methods. Adult inbred Dark Agouti (DA) kidneys were transplanted, with immediate nephrectomy of recipient kidneys, to (1) ALLO, inbred Albino Surgery (AS) rats; (2) DSBT ALLO, AS rats who received two DA blood transfusions under cover of cyclosporine prior to transplantation; or (3) ISO, DA rats. Grafts were retrieved on day 1, 3, or 5. Apoptosis was assessed by TUNEL. RNA was extracted and reverse transcribed to cDNA for quantification by real-time PCR, relative to the 18s housekeeping gene. Results. Apoptosis was negligible in ISO while it increased in allograft groups from day 1. On day 5, apoptosis in ALLO (114.0 ′ 30.6), involved renal tubular cells and leukocytes compared to DSBT ALLO (9.7 ′ 4.0) and ISO (0.9 ′ 0.3) involving leukocytes only. On day 1, DSBT ALLO had higher expression of Bax than ALLO or ISO. On day 3, DSBT ALLO and ALLO had higher TGF-β 1 mRNA than ISO. On day 5, Bcl-2 expression was significantly decreased (P <.001) in ALLO compared to DSBT ALLO and ISO. Bad and Bid were higher in DSBT ALLO than in ALLO. TGF-β 1 was higher in DSBT ALLO compared to ISO. Conclusions. Decreased expression of anti-apoptotic Bcl-2 gene may be implicated in increased apoptosis in rejecting allograft while expression of pro-apoptotic genes may be involved in the establishment of operational tolerance.