The Banff 97 working classification refines earlier schemas and represents input from two classifications most widely used in clinical rejection trials and in clinical practice worldwide. Major changes include the following: rejection with vasculitis is separated from tubulointerstitial rejection; severe rejection requires transmural changes in arteries; "borderline" rejection can only be interpreted in a clinical context; antibody-mediated rejection is further defined, and lesion scoring focuses on most severely involved structures. Criteria for specimen adequacy have also been modified. Banff 97 represents a significant refinement of allograft assessment, developed via international consensus discussions.

We conclude that some changes observed in cellular senescence in vitro do occur in human kidney with age, particularly in the renal cortex, in some cases correlating with histologic features. P16INK4a emerged with the most consistent correlations with age and histologic changes and inversely correlated with cell replication.

Background— Glutaraldehyde fixation (G-F) decreases but likely does not eliminate the antigenicity of bioprosthetic heart valves. Rejection (with secondary dystrophic calcification) may be why G-F xenograft valves fail, especially in young patients, who are more immunocompetent than the elderly. Therefore, we sought to determine whether rejection of G-F xenograft occurs and to correlate this with graft calcification. Methods and Results— Ascending aortas/valves (from rats [syngeneic] or guinea pigs [xenogeneic]) were transplanted (fresh or after 48 hour of G-F) into the infrarenal aortas of young rat recipients for 20 days. A xenogeneic group was also treated with steroids until graft harvest. The valves and media/adventitia were scored blindly for inflammation (0 to 4). Percent graft infiltration by T cells/macrophages was determined (immunohistochemistry), and rat IgG ELISAs were performed. There was >3 times more valve inflammation, >10 times more valve T-cell/macrophage infiltrate, and >3 times antibody rise in the G-F xenogeneic groups compared with the fresh syngeneic or the G-F syngeneic groups ( P <0.05). There was >2 times more adventitial inflammation and T-cell/macrophage infiltrate in the xenogeneic groups ( P <0.05). Steroid treatment decreased inflammation and antibody rise in the xenogeneic groups ( P <0.05). Correlation analysis revealed media/adventitia inflammation ( P =0.02) and percent macrophage ( P =0.01) infiltration to be predictors of calcification. Conclusions— G-F xenografts have cellular/humoral rejection and calcify secondarily.

Some features of kidney transplants with dysfunction overlap the lesions of aging, such as tubular atrophy and interstitial fibrosis (TA/IFINK4a , suggesting that it was not simply a feature of atrophy. Epithelial p16INK4a staining was not increased in transplants with good function, but was increased in diseased native kidneys. The finding of increased p16INK4a expression in renal transplants and diseased kidneys with TA/IF and impaired function supports the concept that some cell senescence changes that accompany aging are also induced by injury and disease stresses. Thus, aging, injury and disease may share common pathways involving somatic cell senescence.

No abstract

The biological processes responsible for somatic cell senescence contribute to organ aging and progression of chronic diseases, and this may contribute to kidney transplant outcomes. We examined the effect of pre-existing donor aging on the performance of kidney transplants, comparing mouse kidney isografts and allografts from old versus young donors. Before transplantation, old kidneys were histologically normal, but displayed an increased expression of senescence marker p16 INK4a . Old allografts at day 7 showed a more rapid emergence of epithelial changes and a further increase in the expression of p16 INK4a . Similar but much milder changes occurred in old isografts. These changes were absent in young allografts at day 7, but emerged by day 21. The expression of p16INK4a remained low in young kidney allografts at day 7, but increased with severe rejection at day 21. Isografts from young donors showed no epithelial changes and no increase in p16INK4a . The measurements of the alloimmune response-infiltrate, cytology, expression of perforin, granzyme B, IFN-c and MHC-were not increased in old allografts. Thus, old donor kidneys display abnormal parenchymal susceptibility to transplant stresses and enhanced induction of senescence marker p16INK4a , but were not more immunogenic. These data are compatible with a key role of somatic cell senescence mechanisms in kidney transplant outcomes by contributing to donor aging, being accelerated by transplant stresses, and imposing limits on the capacity of the tissue to proliferate.

The method described in this study using independent validation samples can be envisioned to test utility of the identified genes in assessing age-related changes that contribute to decline in renal function.

SummaryAlthough thyroglobulin (Tg), the thyroid prohormone, is well known as a T cell dependent autoantigen in human and experimental autoimmune thyroid disease, very little is known about the molecular basis of Tg recognition by T cells. In this paper, we have characterized the epitopes recognized by .two clonotypically distinct, murine Tg autoreactive T cell hybridomas, CH9 and ADA2 . In vitro iodination of a Tg preparation which was deficient in in vivo organified iodine was first used to confirm our previous observation that these T cells recognize iodination-related epitopes in the Tg molecule . Affinity chromatography of tryptic peptides derived from normally iodinated human Tg revealed that these epitopes were exclusively located in thyroxine (T4) containing peptides. Through the use of synthetic T4-containing peptides, representing the four major hormonogenic sites in Tg, we demonstrated that both CH9 and ADA2 recognize an epitope containing the T4 at position 2553 in human Tg. Sets of overlapping 5mer to 12mer peptides around this T4 showed that the most potent peptide was a 9mer beginning at Asp 2551. The T4 was shown to be a critical residue, since its replacement with any of the 20 naturally occurring amino acids produced only nonstimulatory peptides. Since the T cell hybridomas could also be stimulated by major histocompatibility complex class II positive (interferon-, y-treated) thyroid epithelial cells in vitro, and their parent T cell lines can induce thyroiditis on adoptive transfer, the T4-containing Tg sequence described here is implicated as a pathogenic epitope in murine thyroid autoimmunity. T he production of the thyroid hormones thyroxine (T4),t tri-iodothyronine (T3) and reverse T3 (rT3) is dependent on the organification of iodine into thyroglobulin (Tg), the major protein product of the thyroid (1, 2) . This involves thyroid peroxidase catalyzed iodination of tyrosine residues in Tg to form mono-and di-iodotyrosines and their subsequent crosslinking to form the iodothyronines T3 and T4. These mature Tg molecules are stored in a colloidal form in the lumen of thyroid follicles. Secretion of T4 and T3 involves the endocytosis and subsequent proteolysis of colloidal Tg, which releases the hormone residues for diffusion into the circulation . The recent cloning of the genes coding for Tg from several species has allowed the precise localization 1 Abbreviations used in this paper.