Downregulation of T cell receptor expression by CD8(+) lymphocytes in kidney allografts.

Allospecific CD8(+) T lymphocytes are an important component of the cellular response in allograft rejection. These cells recognize and engage MHC class I antigens, leading to allospecific cytolytic responses and graft rejection. In mouse kidney allografts that survive to 3 wk after transplantation, we noted that the majority of CD8(+) cells do not express surface alpha/beta T cell receptor alpha/beta(TCR), gamma/deltaTCR, or CD3. However, these CD8(+)TCR- cells did express surface markers characteristic of T cells, including Thy1.2, CD2, and CD5. In addition, the CD8(+)TCR- cells expressed mRNA for TCR Vbeta gene families, and nearly half stained positive for cytoplasmic Vbeta8 protein, suggesting that they are T cells that have downregulated alpha/betaTCR protein expression from their cell surfaces. When these surface TCR- cells were isolated from kidney allografts by flow cytometry and cultured in the presence of either allogeneic or syngeneic stimulators, nearly 100% of cells reacquired normal levels of alpha/betaTCR expression with disproportionate usage of Vbeta8 chains. After recovery of their surface TCR expression, the CD8(+)TCR- population demonstrated strong alloreactivity in culture. These results suggest that the substantial number of CD8(+)TCR- cells found in long-term surviving mouse kidney allografts are alpha/beta-T cells that have downregulated their cell surface expression of TCR. While in other systems this phenotype may identify cells that have engaged antigen, our results indicate that loss of TCR expression by CD8(+) kidney graft-infiltrating cells may not depend on antigen engagement and that elements in the microenvironment of the kidney graft play a key role in this process. Factors that modulate expression of TCR by graft-infiltrating lymphocytes may have an important role in regulating rejection responses.     

Delirium in liver transplantation candidates: discriminant analysis of multiple test variables

We report the results of electroencephalograms, Mini-Mental State exam, Trailmaking Tests A and B, and serum albumin levels in 108 consecutive liver transplantation candidates. We compared test results to a clinical DSM-III diagnosis of delirium. Although each variable could differentiate between the two groups (delirium n = 18; nondelirium n = 90) at a statistically significant level, a discriminant analysis involving either all variables or only three particular variables (Trailmaking B, EEG code, and albumin) resulted in the highest specificity (97.8%) and sensitivity (83.3%), with a correct classification of 95.4% of subjects. The analysis also generates an equation that can be applied to clinical situations to enhance the accurate recognition of delirium. In addition, to explain abnormal Trailmaking B scores and/or EEGs in subjects who did not otherwise meet DSM-III criteria for delirium, we suggest the presence of a "subclinical delirium."