J A Madrigal

Detection of vimentin-specific autoreactive CD8+ T cells in cardiac transplant patients.

Background. Evidence is emerging that autoimmunity can play a role in allograft rejection. Reports have described the presence of autoantibodies in transplant patients and CD4+ autoreactive T cells in rodent models of allograft rejection. The objective of this study was to seek evidence of CD8+ T-cell–mediated autoimmunity in the transplant setting. The authors have previously observed autoimmunity to the non-polymorphic cytoskeletal protein vimentin in cardiac transplant patients. In this study, vimentin antibody-positive patients were screened for the presence of vimentin-specific self-major histocompatibility complex class I-restricted CD8+ T cells. Methods. Two peptide sequences from vimentin that bound HLA-A*0201 were identified and fluorochrome-labeled A*0201 tetramers with each peptide were constructed to screen for vimentin-specific T cells. Results. Tetramer-binding CD8+ T cells were detected in peripheral blood lymphocytes from two of six patients after expansion by in vitro stimulation with peptide. Tetramer-binding T cells produced interferon-γ in an antigen-specific fashion. No autoreactive T cells specific for vimentin were detected after peptide stimulation of T cells from eight healthy A*0201-positive volunteers. Conclusions. This finding is the first evidence of CD8+ T-cell–mediated autoimmunity in human transplant patients.

Scoring for HLA matching? A clinical test of HistoCheck

The HistoCheck1 software is offered as a tool that is capable of assessing the allogenicity (matching score) between any pair of clinically relevant HLA class I... alleles. This is a brave attempt to aid Transplant Physicians in making the often difficult choice between two or more mismatched (unrelated) donors, when no completely matched donor is available. This internet-based software provides a score that takes into account both the functional and the structural difference between two HLA alleles at one locus. The predictive value of HistoCheck is based on the presumption that transplant success is improved by selecting a donor with an HLA type most similar to the patient.

Exploiting beneficial alloreactive T cells

Although the T‐cell response to allogeneic cells is typically regarded as a detrimental phenomenon responsible for rejection of transplanted allografts and graft‐vs.‐host disease following haematopoietic stem cell transplantation, beneficial components also exist within the alloreactive population. Alloreactive T cells specific for tumour antigens can contribute to the elimination of malignant cells, and alloantigen‐specific regulatory T cells can promote transplant tolerance. The challenge is to separate the good from the bad. We review how the identification, isolation and manipulation of beneficial alloreactive T cells has grown from a greater understanding of the molecular basis of the T‐cell alloresponse and how alloaggression could be exploited for immunotherapy.

Assessing the toxic effects of DMSO on cord blood to determine exposure time limits and the optimum concentration for cryopreservation

Advantages of using cord blood (CB) over other sources of haematopoietic progenitor cells, such as bone marrow, include the ability to cryopreserve and bank the samples until requested for a transplant. Cryopreservation requires the addition of a cryoprotectant to prevent the formation of intracellular ice during freezing. Dimethyl sulphoxide (DMSO) is commonly used at a concentration of 10% (v/v); however, there is evidence to suggest this chemical is toxic to cells as well as to patients after infusion.

No impact of NOD2/CARD15 on outcome after SCT: a reply.

In a recent issue of Bone Marrow Transplantation, Dr Sairafi et al. reported the results of a retrospective study to investigate the impact of NOD2/CARD15 single nucleotide polymorphisms (SNPs) on the outcome of allogeneic haematopoietic stem cell transplants (HSCT). They found no significant correlation between the presence of a NOD2/ CARD15 SNP and the incidence of acute GVHD, TRM, relapse-free survival or overall survival. We have recently reported the results of a retrospective analysis of the impact of NOD2/CARD15 SNPs on the outcome of 196 unrelated donor HSCT (UD-HSCT) pairs where the recipient was diagnosed with acute leukaemia. We found that the presence of a NOD2/CARD15 SNP correlated with a significant reduction in overall survival because of an increase in disease relapse. Numerous other studies have shown the presence of SNPs to have a detrimental effect on the outcome of HSCT although the actual complication observed varies between groups and is thought to be dependent on specific characteristics of the cohort itself. The authors discussed the possibility that differences in patient characteristics and transplant regimens between their cohort and those previously reported may explain why they failed to see significant effects on outcome where others have. Thus, we looked for any differences between the cohort described by Sairafi et al. and the patients in our study that might explain the divergent results. The most obvious difference is that their study comprised a mixture of related and UD sources, whereas our study focused solely on UD transplants. We found that the effect of NOD2/CARD15 SNPs was seen only in recipients with acute leukaemia and more specifically the effect was more pronounced in the ALL subgroup (Figure 1). This marked effect in acute leukaemia has also been reported in a related donor cohort, although, as previously, the outcome affected was different in the two studies based on differences in the clinical protocols used. As 37% of the cohort studied by Sairafi et al. were recipients whose diagnosis was not acute leukaemia, the lack of effect seen in these recipients may mask any effect of the NOD2/ CARD15 SNPs in this study. The use and method of T-cell depletion was noticeably different when compared with our data, which we and others believe contributes significantly to the effect of any polymorphisms. In addition, the majority of transplants in the Sairafi study occurred when the recipient was considered to be in a lowrisk stage of their disease, which in itself may predict for a reduced risk of disease relapse. Finally, the frequency of NOD2/CARD15 SNPs seen in their study were markedly lower than in our cohort and in other HSCT studies. (The reported overall SNP frequency was 18% as compared with 27–29% in other studies.) There is evidence to suggest that there is geographic variation in the prevalence of NOD2/CARD15 SNPs, which may explain the low frequency seen. Thus, the lack of correlation to transplant outcome may be due to a lower prevalence of SNPs in this cohort. It would be of interest to see if Sairafi et al. were able to see an effect in more homogeneous subgroups of their cohort, particularly in the acute leukaemia recipients and the UD pairs. This study adds much to the discussion that

A novel HLA-DPB1 allele, DPB1*125:01, identified by sequence-based typing in an Indian individual.

A novel DPB1*125:01 allele differs from DPB1*26:01:02 at two positions in exon 2, leading to changes at codons 9 and 35.

Identification of a novel KIR3DL1*072 allele by sequence-based typing.

We report a novel KIR3DL1*072 allele that was found using a sequence-based typing approach.