Cytotoxic T-cell-mediated defense against infections in human liver transplant recipients.

Previous studies have shown that postoperative infection is highest in transplant recipients with preexisting high levels of cytotoxic T lymphocytes (CTLs). To study this phenomenon, 106 adult liver transplant recipients were divided into 3 groups, based on hierarchical clustering of the CD3(+)CD8(+)CD45 isoform fractions prior to living donor liver transplantation (LDLT). Group I had the highest naive T-cell levels (subset CD45RO(-)CCR7(+)), Group II had the highest effector/memory (EM) T-cell levels (subset CD45RO(+)CCR7(-)), and Group III had the highest effector T-cell levels (subset CD45RO(-)CCR7(-)). In Group I, CTLs upregulated in response to invading pathogens much earlier and more rapidly than the other groups; this response was associated with CD4(+) T-cell help, downregulation of CD27(+)CD28(+) subsets, and upregulation of interferon-gamma and perforin expression. In contrast, in Groups II and III, CTLs upregulated slowly following persistent viral infection and did not respond efficiently to acute infection. In addition, Group II's cytolytic responses were due mainly to upregulation of the CD8(+) EM T-cell fraction, whereas Group III's cytolytic responses were attributable to upregulation of effector T cells. The prevalence of EM or effector T cells was dependent on differentiation of the CD8(+) phenotype before LDLT. In conclusion, in most infected transplant recipients who died, generation of CD8(+) CTLs had been suppressed without associated CD4(+) T-cell help.