Kidney Transplantation and Cellular Immunity Dynamics: Immune Cell Alterations and Association with Clinical and Laboratory Parameters.

Background/Objectives: The purpose of this study was to evaluate numerical changes in immune cells after successful kidney transplantation and associate their recovery with clinical and laboratory factors. Methods: In 112 kidney transplant recipients, we performed flow cytometry to evaluate counts of CD4+, CD8+, and regulatory T cells (Tregs), as well as natural killer (NK) cells, before kidney transplantation (T0) and three (T3), six (T6), and twelve (T12) months later. The results were associated with the recipient's age, cold ischemia time (CIT), the type of donor, dialysis method and vintage, and graft function in one year. Results: Total and CD8+ T cell counts increased gradually one year post transplantation in comparison with pre-transplantation levels, whereas the number of CD4+ T cells and Tregs increased, and the number of NK cells decreased in the first three months and remained stable thereafter. The recipient's age was negatively correlated with total, CD4+, and Treg counts at T12, whereas CIT affected only total and CD4+ T cell count. Moreover, recipients receiving kidneys from living donors presented better recovery of all T cell subsets at T12 in comparison with recipients receiving kidneys from cadaveric donors. Patients on peritoneal dialysis had increased numbers of total and CD8+ T cells, as well as NK cells. Finally, estimated glomerular filtration rate was positively correlated with Treg level and potentially CD4+ T cells one-year post transplantation. Conclusions: Successful kidney transplantation results in the recovery of most T cell subsets. Lower recipient age and better graft function contribute to increased T cell counts, whereas donor type and dialysis modality are the most important modifiable factors for optimal immune recovery.

Vaccination with Tozimameran Induces T-Cell Activation, but Not Senescent or Exhaustive Alterations, in Kidney Transplant Recipients.

BACKGROUND: Multiple vaccinations have potential inimical effects on the immune system aging process. We examined whether response to SARS-CoV-2 vaccination with Tozinameran is associated with immunosenescence and immunoexhaustion in kidney transplant recipients (KTRs). METHODS: In this prospective observational study, we observed 39 adult kidney transplant recipients (KTRs) who had no pre-existing anti-SARS-CoV-2 antibodies and were on stable immunosuppression. CD4+ and CD8+ T-cell subpopulations [comprising CD45RA+CCR7+ (naïve), CD45RA-CCR7+ (T-central memory, TCM), CD45RA-CCR7- (T-effector memory, TEM) and CD45RA+CCR7- (T-effector memory re-expressing CD45RA, TEMRA, senescent), CD28- (senescent) and PD1+ (exhausted)] were evaluated at 2 time points: T1 (48 h prior to the 3rd), and T2 (3 weeks following the 3rd Tozinameran dose administration). At each time point, patients were separated into Humoral and/or Cellular Responders and Non-Responders. RESULTS: From T1 to T2, CD4+TCM and CD8+TEM were increased, while naïve CD4+ and CD8+ proportions were reduced in the whole cohort of patients, more prominently among responders. At T2, responders compared to non-responders had higher CD8+CD28+ [227.15 (166) vs. 131.44 (121) cells/µL, p: 0.036], lower CD4+CD28- T-lymphocyte numbers [59.65 (66) cells/µL vs. 161.19 (92) cells/µL, p: 0.026] and percentages [6.1 (5.5)% vs. 20.7 (25)%, p: 0.04]. CONCLUSION: In KTRs, response to vaccination is not associated with an expansion of senescent and exhausted T-cell concentrations, but rather with a switch from naïve to differentiated-activated T-cell forms.

Complement and Non-Complement Binding Anti-HLA Antibodies Are Differentially Detected with Different Antigen Bead Assays in Renal Transplant Recipients.

Two semi-quantitative, Luminex-based, single-antigen bead (SAB) assays are available to detect anti-HLA antibodies and evaluate their reactivity with complement binding. Sera from 97 patients with positive panel reactive antibody tests (>5%) were analyzed with two SAB tests, Immucor (IC) and One-Lambda (OL), for anti-HLA antibody detection and the evaluation of their complement-binding capacity. IC detected 1608/8148 (mean fluorescent intensity (MFI) 4195 (1995-11,272)) and 1136/7275 (MFI 6706 (2647-13,184)) positive anti-HLA class I and II specificities, respectively. Accordingly, OL detected 1942/8148 (MFI 6185 (2855-12,099)) and 1247/7275 (MFI 9498 (3630-17,702)) positive anti-HLA class I and II specificities, respectively. For the IC assay, 428/1608 (MFI 13,900 (9540-17,999)) and 409/1136 (MFI 11,832 (7128-16,531)) positive class I and II specificities bound C3d, respectively. Similarly, OL detected 485/1942 (MFI 15,452 (9369-23,095)) and 298/1247 (MFI18,852 (14,415-24,707)) C1q-binding class I and II specificities. OL was more sensitive in detecting class I and II anti-HLA antibodies than IC was, although there was no significant difference in the number of class II specificities per case. MFI was higher for complement vs. non-complement-binding anti-HLA antibodies in both assays. Both methods were equal in detecting complement-binding anti-HLA class I antibodies, whereas the C3d assay was more sensitive in detecting complement-binding anti-HLA class II antibodies.

Activation of the AtoSC two-component system in the absence of the AtoC N-terminal receiver domain in E. coli.

The AtoSC two-component system in E. coli consists of the AtoS sensor kinase and the AtoC response regulator. It regulates positively the transcriptional activation of atoDAEB operon, encoding enzymes involved in short-chain fatty acid catabolism upon acetoacetate-mediated induction. AtoSC acting on atoDAEB operon, regulates the biosynthesis and the intracellular distribution of short-chain poly-(R)-3-hydroxybutyrate (cPHB). A phosphorylation-incompetent AtoC form was constructed lacking its N-terminal receiver domain, trAtoC, to study the effects of AtoC domains on cPHB biosynthesis and atoDAEB operon regulation. Both cPHB biosynthesis and atoDAEB gene expression were regulated positively by trAtoC in the absence of any inducer in E. coli of both atoSC (+) and ΔatoSC genotypes. The presence of acetoacetate or spermidine further promoted these trAtoC actions. Competitive regulatory functions between the full length AtoC and trAtoC were observed referring to atoDAEB and cPHB targets as well as growth of trAtoC-overproducing atoSC (+) cells on butyrate as the sole carbon source. trAtoC in contrast to the wild-type AtoC presented different modes of cPHB and atoDAEB regulation in the presence of compounds involved in fatty acid metabolism including CoA-SH, acetyl-CoA, sodium acetate or 3-hydroxybutyryl-CoA. These data provide evidence for a role of the AtoC N-terminal receiver domain in regulating the biological activities of AtoSC as well as additional mechanisms of interactions between the AtoSC constituents including their established inducers or new effectors towards the accomplishment of the AtoSC TCS signal transduction.