Gilles Folléa

Frequency and Clinical Implications of Development of Donor-Specific and Non–Donor-Specific HLA Antibodies after Kidney Transplantation

The involvement of immunologic and nonimmunologic events in long-term kidney allograft failure is difficult to assess. The development of HLA antibodies after transplantation is the witness of ongoing reactivity against the transplant, and several studies have suggested that the presence of HLA antibodies correlates with poor graft survival. However, they have not discriminated between donor-specific (DS) and non-specific (NDS) antibodies. A total of 1229 recipients of a kidney graft, transplanted between 1972 and 2002, who had over a 5-yr period a prospective annual screening for HLA antibodies with a combination of ELISA, complement-dependent cytotoxicity, and flow cytometry tests were investigated; in 543 of them, the screening was complete from transplantation to the fifth year postgrafting. Correlations were established between the presence and the specificity of the antibodies and clinical parameters. A total of 5.5% of the patients had DS, 11.3% had NDS, and 83% had no HLA antibodies after transplantation. NDS antibodies appeared earlier (1 to 5 yr posttransplantation) than DS antibodies (5 to 10 yr). In multivariate analysis, HLA-DR matching, pretransplantation immunization, and acute rejection were significantly associated with the development of both DS and NDS antibodies and also of DS versus NDS antibodies. The presence of either DS or NDS antibodies significantly correlated with lower graft survival, poor transplant function, and proteinuria. Screening of HLA antibodies posttransplantation could be a good tool for the follow-up of patients who receive a kidney transplant and allow immunosuppression to be tailored.

Identification of the antibodies involved in B-cell crossmatch positivity in renal transplantation

Background. The significance of a positive B-cell crossmatch (BCM) in kidney transplantation has always been controversial in the evaluation of its implications on graft survival and specificity of the antibodies involved. Methods. We have investigated the sera of 62 recipients of a kidney allograft transplanted across a positive BCM (T negative) for the presence of autoantibodies and anti-human leukocyte antigen (HLA) class I and II antibodies, using a combination of lymphocytotoxicity, enzyme-linked immunosorbent assay (ELISA), and flow cytometry tests. The controls were the 930 patients transplanted over the same period of time with a negative T and BCM. Results. Autoantibodies were detected in 16%, and donor specific anti-HLA class II antibodies, mainly DQ, in 23% of the patients. None had antibodies against donor HLA class I. The target of the antibodies was not identified in 61%. Graft survival was comparable in the controls and in the +BCM patients, with nondonor-specific HLA reactivity. Patients with donor-specific anti-HLA class II antibodies had lower early graft survival and a higher incidence of vascular rejection. However, long-term allograft survival was similar to that of the other groups. Conclusion. These data suggest that in 77% of the patients, BCM positivity was not related with anti-HLA antibodies, and, in this case, graft survival was similar to that of the −BCM controls. In a minority of patients, anti-HLA class II antibodies were responsible for the +BCM, and their presence was associated with lower early, but not long-term, graft survival. Consequently, a +BCM should not systematically contraindicate kidney transplantation.

Autologous and allogeneic HLA KIR ligand environments and activating KIR control KIR NK-cell functions.

NK‐cell function is regulated by a balance between inhibitory and activating killer cell immunoglobulin‐like receptors (KIR) that specifically recognize HLA class I molecules. Using KIR‐specific mAb to discriminate between KIR2DS1 and KIR2DL1 receptors, we show that KIR2DS1+ NK cells are C2‐alloreactive only from C2− individuals. Moreover, using an in vitro model of NK‐cell expansion, we show here that the frequency of KIR2DL1+ NK cells is significantly higher in the absence of C2 ligand on stimulator EBV‐B cells than in its presence. This observation was made regardless of the presence or absence of the autologous C2 ligand, suggesting that the C2− EBV‐B stimulator cells used in this in vitro model could activate unlicensed KIR2DL1+ NK cells. In the case of KIR2DL1+/S1+ genotyped individuals, KIR2DS1+ NK‐cell frequency was increased after stimulation with C2+ compared with C2− stimulator B cells, but only from C2− individuals. Altogether, these data highlight the C2 alloreactivity of KIR2DS1+ NK cells that is only observed in C2− individuals. These results provide new insights into the way in which NK KIR cell expansion might be regulated in an allogeneic environment.

Discrimination between the main activating and inhibitory killer cell immunoglobulin-like receptor positive natural killer cell subsets using newly characterized monoclonal antibodies

Natural killer (NK) cells are key components of the innate anti‐viral and anti‐tumour immune responses. NK cell function is regulated by the interaction of killer cell immunoglobulin‐like receptors (KIR) with human leucocyte antigen (HLA) class I molecules. In this study, we report on the generation of KIR‐specific antibodies allowing for discrimination between activating and inhibitory KIR. For this purpose, BALB/c mice were immunized with human KIR2DS2 recombinant protein. The precise specificity of KIR2DS2‐specific clones was determined on KIR‐transfected BW cells and KIR‐genotyped NK cells. When used in combination with EB6 (KIR2DL1/2DS1) or GL183 (KIR2DL2/2DL3/2DS2), two KIR‐specific monoclonal antibodies (mAbs), 8C11 (specific for KIR2DL1/2DL2/2DL3/2DS2) and 1F12 (specific for KIR2DL3/2DS2), discriminated activating KIR2DS1 (8C11− EB6+) from inhibitory KIR2DL1 (8C11+ GL183−) and KIR2DL2 (1F12− GL183+), while excluding the main HLA‐Cw‐specific KIR. Using these mAbs, KIR2DS1 was shown to be expressed on the surface of NK cells from all individuals genotyped as KIR2DS1+ (n = 23). Moreover, KIR2DS1 and KIR2DL1 were independently expressed on NK cells. We also determined the amino acid position recognized by the 8C11 and 1F12 mAbs, which revealed that some KIR2DL1 allele‐encoded proteins are not recognized by 8C11. Because most available anti‐KIR mAbs recognize both inhibitory and activating forms of KIR, these newly characterized antibodies should help assess the expression of activating and inhibitory KIR and their functional relevance to NK biology.

Phenotypic and Functional Analyses of KIR3DL1+ and KIR3DS1+ NK Cell Subsets Demonstrate Differential Regulation by Bw4 Molecules and Induced KIR3DS1 Expression on Stimulated NK Cells

Recently, the Z27 mAb was shown to recognize the NK cell-activating receptor KIR3DS1, and several genetic studies suggest that the most probable ligands of KIR3DS1 are HLA class I molecules with the Bw4 motif. Despite these findings, the attempts to establish a functional interaction between KIR3DS1 and its potential ligand have been unsuccessful. Here, we study the proliferation and cytotoxicity of KIR3DS1+ NK cells, compared with KIR3DL1+ NK cells, according to the Bw4+ or Bw4− allogeneic environment. Our results show for the first time that KIR3DS1 expression on NK cells can be induced after exposure to stimulator cells (221, K562, EBV-B cell lines, and B cells), polyinosinic-polycytidylic acid, IL-15, or IL-2. Furthermore, whereas KIR3DL1+ NK cell proliferation and cytotoxicity were inhibited in a Bw4+ but not a Bw4− context, KIR3DS1+ NK cell functions were not influenced by the presence of Bw4 on target cells. Nevertheless, despite the absence of demonstrated regulation of KIR3DS1+ NK cell functions by HLA-Bw4 molecules, we found a higher KIR3DS1+ NK cell frequency and higher levels of KIR3DS1 expression in Bw4+ compared with Bw4− individuals. Altogether, these results suggest that KIR3DS1 does not recognize HLA-Bw4 molecules in a physiological context, and they highlight the induced expression of KIR3DS1 observed on stimulated NK cells and the higher frequency of KIR3DS1+ NK cells in Bw4+ individuals. Because a protective KIR3DS1-Bw4 association has been reported in viral infections, our results further the understanding of the role of KIR3DS1+ NK cells in controlling viral infections.

Identification and quantification of fetal red blood cells in maternal blood by a dual‐color flow cytometric method: evaluation of the Fetal Cell Count kit

BACKGROUND: As an alternative to the cumbersome Kleihauer‐Betke test (KBT), flow cytometry represents a powerful method for the identification and quantification of fetal red blood cells (RBCs) in maternal circulation.

Development of monoclonal antibodies directed against cocaine and cocaethylene: potential new tools for immunotherapy.

Cocaine abuse is a major health problem, with the number of overdose-related incidents on a constant increase. Monoclonal antibodies against cocaine and its major toxic metabolite cocaethylene, have been developed for immunotherapeutical neutralization in vivo. A series of monoclonal antibodies with high affinity for cocaethylene and cocaine were obtained. Clones DASm244-4D8A4A4 (4D8) and DASm244-5B3C3C6 (5B3) were selected and fully characterized. The antibodies secreted exhibited 1.40 x 10(8) and 3.69 x 10(7) M(-1) affinity constants for [3H]-cocaine and cocaethylene, respectively. In addition to cocaine, they bound to cocaethylene and did not recognize non-toxic cocaine metabolites. They did not bind to blood cells, indicating that they may be potential tools for cocaine neutralization in vivo in cases of overdose.

Investigation of the impact of HLA-DPB1 matching status in 10/10 HLA matched unrelated hematopoietic stem cell transplantation: Results of a French single center study

The impact of HLA-DPB1 mismatches after unrelated hematopoietic stem cell transplantation (HSCT) remains controversial. We retrospectively analyzed the impact of permissive/non-permissive HLA-DPB1 mismatches on the outcome of 141 patients who underwent 10/10 HLA allelic-matched unrelated HSCT. Each pair was classified according to the 3 (TCE3) and 4-group (TCE4) algorithm based on DPB1 alleles immunogenicity. Outcome analysis revealed that TCE3 and TCE4 non-permissive HLA-DPB1 disparities were not associated with worsened overall survival, relapse risk neither risk of acute GvHD. Overall, this single center retrospective study does not confirm the adverse prognostic of non-permissive HLA-DPB1 mismatches.