Serologic allogeneic chimerism

Cell transplant techniques: engraftment detection of cells

The use of isolated human hepatocyte infusions to treat human disease will require safe, acceptable, reliable, and reproducible measures of engraftment and function of the donor liver cell. Cell transplant for inborn errors of hepatic metabolism can be followed by measuring the specific protein missing from the recipient, expressed by the transplanted unmodified donor hepatocytes expressing the genes in question. This chapter will focus on the clinical techniques successful in identifying the engraftment and function of donor human hepatocytes when no specific identifiable genes are expressed by donor hepatocytes in acute and chronic liver diseases treated by cell infusion. Radiolabeling and dye labeling techniques, DNA typing of HLA class I alleles, soluble class I HLA ELISA, real-time quantitative PCR techniques including short tandem repeats analysis will be detailed and critiqued.

Rapid decreases in donor-specific cytotoxic T lymphocyte precursor frequencies and graft outcome after liver and lung transplantation

BACKGROUND

A decrease in donor-specific T cell precursor frequencies as seen late, one or more years, after transplantation is assumed to reflect transplantation tolerance, a condition important for long term acceptance of the allograft. However, such late decreases also occur in recipients that developed chronic transplant dysfunction questioning its relevance in transplantation tolerance. We investigated whether early, i.e., the first 6 months, decreases in donor-specific T cell precursor frequencies reflect transplantation tolerance and predict graft outcome after liver and lung transplantation.

METHODS

Donor and third party specific cytotoxic (CTLp) and helper T lymphocyte precursor (HTLp) frequencies were analyzed in pretransplant and 1 (or 2) and 6-month blood samples taken from liver and lung recipients and were correlated with graft outcome.

RESULTS

In liver allograft recipients with good graft function (n=7), mean donor-specific CTLp frequencies decreased as early as 1 month after transplantation and remained low thereafter. In contrast, mean CTLp frequencies did not decrease in liver allograft recipients with chronic transplant dysfunction (n=6). In lung allograft recipients, donor-specific CTLp frequencies remained relatively high and frequencies were not different between recipients without (n=6) or with (n=6) chronic transplant dysfunction. Donor-specific HTLp frequencies did not change significantly after liver or lung transplantation and did not differ between recipients without or with chronic transplant dysfunction.

CONCLUSIONS

An early decrease in donor-specific CTLp correlates with good graft outcome after liver transplantation. Such rapid decreases in alloreactivity do not occur after lung transplantation illustrating the unique capacity of liver allografts to induce transplantation tolerance.

Defining hepatocellular chimerism in a liver failure patient bridged with hepatocyte infusion

BACKGROUND

A practical method of monitoring engraftment by transplanted hepatocytes for the purpose of bridging human liver failure to native regeneration is described.

METHODS

A previously healthy 37-year-old female with a 2-week history of a febrile illness presented with fulminant liver failure. Findings on admission included the following: illicit drug use, serum hepatitis B surface antigen positive, grade 1 encephalopathy, prothrombin time (pt) >100 sec, F7<1%, NH3 150 micromol/L, alanine aminotransferase 4079 U/L, total bilirubin level 11.4 mg/dl, and glucose 70 mg/dl (on IV D10). With immunosuppression, 8.8x10(8), 96% viable human hepatocytes were intraportally infused. Clinical chemistries, total sHLA class I, and ELISA to measure donor-specific sHLA-A1 and -B8 were recorded. Serial transjugular liver biopsies were performed and pooled for histological examination, DNA extraction, and HLA DNA typing.

RESULTS

The patient fully recovered. At months 3 and 4 with donor biopsy specimen class I HLA DNA no longer detectable, immunosuppression was tapered off. The patient is clinically normal, serum hepatitis B surface antigen negative at 10 months of follow-up.

CONCLUSIONS

Bridging liver failure with donor hepatocytes with HLA class I antigen disparate from recipients is clinically feasible, and allows for a marker, combined with serial graft histology, to safely wean immunosuppression when native liver regeneration succeeds.

Analysis of the relationship between chimerism and the allgeneic humoral response

BACKGROUND

Persistence of antigens has been suggested to play a role in two opposing immunological phenomena: tolerance and memory. Therefore, we studied the impact of chimerism on alloreactive antibody (allo-Ab) production in kidney transplant patients.

METHODS

Thirty-five female renal transplant recipients of male donor organs were classified into the following groups: group 1, 13 sensitized uremic patients on dialysis; group 2, 5 nonsensitized uremic patients on dialysis; group 3, six sensitized patients experiencing graft rejection (3 acute vascular, 1 acute cellular, and 2 chronic); and group 4, 11 nonsensitized with functioning allografts (9 with good function, 1 with acute cellular rejection, and 1 with chronic rejection). Mean duration of dialysis after graft failure was similar in groups 1 (56+/-29.7 months) and 2 (41.8+/-42.4 months), as was dialysis efficiency. Chimerism was measured indirectly in the peripheral blood lymphocytes by polymerase chain reaction amplification of a specific Y chromosome DNA gene sequence with a detection sensitivity limit of 1 male cell per 1 million female cells. Allo-Ab production was measured by the PRA-STAT enzyme-linked immunosorbent assay (Sangstat) method.

RESULTS

Chimerism was observed in 60% of groups 1 and 2, 83% of group 3, and 82% of group 4. Among all groups, graft existence, irrespective of its function, positively predicted chimerism in 92% with a sensitivity of 88% and a specificity of 78%. In group 3, all three patients with acute vascular rejection had chimerism and donor-specific allo-Abs. In group 4, eight of the nine patients with no rejection had chimerism.

CONCLUSION

Chimerism relates to persistence of allogeneic stimulus irrespective of its function. Chimerism did not confer protection against allo-Ab production or vascular rejection, and its existence was not crucial for sustenance of allo-Ab production.