Kinetics of Cellular and Humoral Immunity in a Successful Case of Positive Crossmatch Kidney Transplantation: A Case Report

B cell depletion with anti-CD20 mAb exacerbates anti-donor CD4+ T cell responses in highly sensitized transplant recipients

Pretransplant desensitization with rituximab has been applied to preformed donor-specific anti-human leukocyte antigen antibody (DSA)-positive recipients for elimination of preformed DSA. We investigated the impact of pretransplant desensitization with rituximab on anti-donor T cell responses in DSA-positive transplant recipients. To monitor the patients' immune status, mixed lymphocyte reaction (MLR) assays were performed before and after desensitization with rituximab. Two weeks after rituximab administration, the stimulation index (SI) of anti-donor CD4+ T cells was significantly higher in the DSA-positive recipients than in the DSA-negative recipients. To investigate the mechanisms of anti-donor hyper responses of CD4+ T cells after B cell depletion, highly sensitized mice models were injected with anti-CD20 mAb to eliminate B cells. Consistent with clinical observations, the SI values of anti-donor CD4+ T cells were significantly increased after anti-CD20 mAb injection in the sensitized mice models. Adding B cells isolated from untreated sensitized mice to MLR significantly inhibited the enhancement of anti-donor CD4+ T cell response. The depletion of the CD5+ B cell subset, which exclusively included IL-10-positive cells, from the additive B cells abrogated such inhibitory effects. These findings demonstrate that IL-10+ CD5+ B cells suppress the excessive response of anti-donor CD4+ T cells responses in sensitized recipients.

Successful Treatment of Chronic Myeloid Leukemia With Dasatinib After Kidney Transplantation: A Case Report

OBJECTIVE

Chronic myeloid leukemia (CML) is a rare malignancy in kidney transplant (KT) recipients. Although dasatinib is the first-line treatment for CML, it has inhibitory activity against CYP3A4; this might increase the blood concentration of tacrolimus (administered to KT patients for immune suppression). Furthermore, tacrolimus can also increase blood concentrations of dasatinib through P-glycoprotein inhibition.

METHODS

Here, we report a case of sustained molecular remission of CML with prolonged first-line dasatinib therapy in a KT recipient being treated with tacrolimus. A 61-year-old woman developed CML-chronic phase (CML-CP) 38 months post KT. Her maintenance immunosuppressive therapy consisted of tacrolimus, mycophenolate mofetil, and methylprednisolone. Considering the potential drug interaction with tacrolimus, dasatinib was administered at a low dose of 50 mg/day. Her immune status was evaluated regularly by assessing the mixed lymphocyte reaction (MLR) using an intracellular carboxyfluorescein diacetate succinimidyl ester (CFSE)-labeling technique; immunosuppressive therapy was adjusted accordingly.

RESULTS

The patient achieved complete hematologic remission (CHR) after 1 month of dasatinib treatment. Six months after dasatinib treatment, she achieved a major molecular response. During the observation period, neither antibody-mediated nor acute cellular rejection were encountered in the patient. She remained in CHR with a major molecular response 12 months after the diagnosis of CML-CP.

CONCLUSION

Data obtained from immune monitoring assays using CFSE-MLR helped us to successfully manage a KT recipient with CML-CP being treated with dasatinib. Drug-drug interactions are a key consideration while designing treatment regimens; such strategies would ensure that drug-drug interactions do not negatively affect the treatment outcomes.

Different sensitivity of rituximab-treatment to B-cells between ABO-incompatible kidney and liver transplantation

A desensitization protocol with rituximab is currently widely used for kidney transplantation (KT) and liver transplantation (LT) across the ABO blood group-incompatible (ABO-I) barrier. However, it remains to be elucidated whether rituximab is equally effective for B-cell and T-cell immune responses in both KT and LT recipients. To clarify these effects of rituximab, we enrolled 46 KT and 77 LT recipients in this study. The proportion of peripheral blood B-cells was determined at the perioperative period. T-cell responses to allostimulation were evaluated by a mixed lymphocyte reaction (MLR) assay. One week after rituximab administration, peripheral B-cells became undetectable in ABO-I KT recipients but remained detectable in some of the ABO-I LT recipients; B-cells were undetectable in both groups by week 2. B-cells remained below the detection limit throughout the first year in the ABO-I KT recipients, whereas they reappeared in the periphery after 6months in the ABO-I LT recipients. There were no significant differences in alloreactive T-cell responses based on MLR analyses between ABO-I and ABO-compatible groups. This study indicates that rituximab has differing B-cell sensitivity between KT and LT recipients and a minimal effect on the alloreactive T-cell responses in KT and LT recipients.

A Phased Desensitization Protocol With Rituximab and Bortezomib for Highly Sensitized Kidney Transplant Candidates

Desensitization protocols comprising plasmapheresis, IVIGs, and rituximab and/or bortezomib have allowed for successful kidney transplantation in some highly HLA-sensitized patients with end-stage renal disease. However, the optimal combination of these therapies and their proper timing remains entirely unknown. We propose a phased desensitization strategy using rituximab followed by bortezomib as a safer method.

METHODS

Three sensitized kidney transplant candidates who could not be desensitized using our conventional protocol, which consists of a single rituximab dose combined with plasmapheresis, were enrolled in this study. When IgM(+) CD27(-) naive B cells reappeared but IgM(+) CD27(+) memory B cells remained undetectable in their peripheral blood, the patients were treated with 1 cycle of bortezomib followed by plasmapheresis.

RESULTS

After bortezomib treatment, patients' donor-specific anti-HLA antibodies (DSA) values were decreased, and cross-match tests were consistently negative. All 3 patients underwent living donor kidney transplantation. They showed immediate renal function, and both DSA and non-DSA were undetectable during the observation period. Neither antibody-mediated rejection nor severe acute cellular rejection was encountered in these patients after transplantation.

CONCLUSIONS

The present cases suggest that a phased use of rituximab and bortezomib can safely desensitize highly sensitized kidney transplant candidates.