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Introduction Crohn’s disease (CD) is a disabling chronic enteropathy sustained by a harmful T-cell response toward antigens of the gut microbiota in genetically susceptible subjects. Growing evidence highlights the safety and possible efficacy of mesenchymal stem cells (MSCs) as a new therapeutic tool for this condition. Therefore, we aimed to investigate the effects of bone marrow-derived MSCs on pathogenic T cells with a view to clinical application. Methods T-cell lines from both inflamed and non-inflamed colonic mucosal specimens of CD patients and from healthy mucosa of control subjects were grown with the antigen muramyl-dipeptide in the absence or presence of donors’ MSCs. The MSC effects were evaluated in terms of T-cell viability, apoptotic rate, proliferative response, immunophenotype, and cytokine profile. The role of the indoleamine 2,3-dioxygenase (IDO) was established by adding a specific inhibitor, the 1-methyl-DL-tryptophan, and by using MSCs transfected with the small interfering RNA (siRNA) targeting IDO. The relevance of cell-cell contact was evaluated by applying transwell membranes. Results A significant reduction in both cell viability and proliferative response to muramyl-dipeptide, with simultaneous increase in the apoptotic rate, was found in T cells from both inflamed and non-inflamed CD mucosa when co-cultured with MSCs and was reverted by inhibiting IDO activity and expression. A reduction of the activated CD4+CD25+ subset and increase of the CD3+CD69+ population were also observed when T-cell lines from CD mucosa were co-cultured with MSCs. In parallel, an inhibitory effect was evident on the expression of the pro-inflammatory cytokines tumor necrosis factor-α, interferon-γ, interleukin-17A and -21, whereas that of the transforming growth factor-β and interleukin-6 were increased, and production of the tolerogenic molecule soluble HLA-G was high. These latter effects were almost completely eliminated by blocking the IDO, whose activity was upregulated in MSCs co-cultured with CD T cells. The use of a semipermeable membrane partially inhibited the MSC immunosuppressive effects. Finally, hardly any effects of MSCs were observed when T cells obtained from control subjects were used. Conclusion MSCs exert potent immunomodulant effects on antigen-specific T cells in CD through a complex paracrine and cell-cell contact-mediated action, which may be exploited for widespread therapeutic use.

A project of the 15th International Histocompatibility Workshop examined the rarity of human leukocyte antigen (HLA) alleles. A section was constructed in the website, www.allelefrequencies.net to contain this data from different sources. A mechanism to search the data was implemented for use by any individual.

Minor histocompatibility (H) antigens are allogeneic target molecules having significant roles in alloimmune responses after human leukocyte antigen–matched solid organ and stem cell transplantation (SCT). Minor H antigens are instrumental in the processes of transplant rejection, graft-versus-host disease, and in the curative graft-versus-tumor effect of SCT. The latter characteristic enabled the current application of selected minor H antigens in clinical immunotherapeutic SCT protocols. No information exists on the global phenotypic distribution of the currently identified minor H antigens. Therefore, an estimation of their overall impact in human leukocyte antigen–matched solid organ and SCT in the major ethnic populations is still lacking. For the first time, a worldwide phenotype frequency analysis of ten autosomal minor H antigens was executed by 31 laboratories and comprised 2,685 randomly selected individuals from six major ethnic populations. Significant differences in minor H antigen frequencies were observed between the ethnic populations, some of which appeared to be geographically correlated., Author Summary Peptides from cellular proteins evoking alloimmune responses in human leukocyte antigen–identical transplantation are called minor histocompatibility (H) antigens. Upon hematopoietic stem cell transplantation (HSCT) for hematological malignancies or for solid tumors, responses to minor H antigens may have detrimental effects, e.g., graft-versus-host-disease and graft rejection, but can also significantly contribute to the eradication of the tumor cells. We designated the latter antigens as “tumor” minor H antigens. Current clinical trials aim at using these tumor minor H antigens to boost the graft-versus-tumor response. So far, it is unclear how frequently the HSCT recipient and donor differ in their minor H antigens and thus how many cancer patients are eligible for minor H antigen-based treatment. Therefore, worldwide 31 laboratories joined forces to determine the genotype and phenotype frequencies of ten autosomally encoded minor H antigens in six ethnic populations. The frequencies vary depending upon ethnic background and geographic location of the population, implying that the potential applicability of the tumor minor H antigens differs from one population to another. Depending on the population, the current theoretical percentages of clinical application of the eight tumor minor H antigens in HLA-matched combinations is estimated at 12% to 34%.

Background Killer cell immunoglobulin-like receptors (KIRs) are a family of inhibitory and activatory receptors that are expressed by most natural killer (NK) cells. The KIR gene family is polymorphic: genomic diversity is achieved through differences in gene content and allelic polymorphism. The number of KIR loci has been reported to vary among individuals, resulting in different KIR haplotypes. In this study we report the genotypic structure of KIRs in 217 unrelated healthy Italian individuals from 22 immunogenetics laboratories, located in the northern, central and southern regions of Italy. Methods Two hundred and seventeen DNA samples were studied by a low resolution PCR-SSP kit designed to identify all KIR genes. Results All 17 KIR genes were observed in the population with different frequencies than other Caucasian and non-Caucasian populations; framework genes KIR3DL3, KIR3DP1, KIR2DL4 and KIR3DL2 were present in all individuals. Sixty-five different profiles were found in this Italian population study. Haplotype A remains the most prevalent and genotype 1, with a frequency of 28.5%, is the most commonly observed in the Italian population. Conclusion The Italian Caucasian population shows polymorphism of the KIR gene family like other Caucasian and non-Caucasian populations. Although 64 genotypes have been observed, genotype 1 remains the most frequent as already observed in other populations. Such knowledge of the KIR gene distribution in populations is very useful in the study of associations with diseases and in selection of donors for haploidentical bone marrow transplantation.

The importance of HLA-DPB1 matching for the outcome of allogeneic hematologic stem cell (HSC) transplantation is controversial. We have previously identified HLA-DPB1*0901 as a target of cytotoxic T cells mediating in vivo rejection of an HSC allograft. Here we show that HLA-DPB1*0901 encodes a T-cell epitope shared by a subset of DPB1 alleles that determines nonpermissive mismatches for HSC transplantation. Several T-cell clones obtained from the patient at the time of rejection showed HLA-DP restricted recognition of allogeneic targets expressing HLA-DPB1*0901, *1001, *1701, *0301, *1401, and *4501, but not other alleles. Based on these findings, we developed an algorithm for prediction of nonpermissive HLA-DPB1 mismatches. Retrospective evaluation of 118 transplantations showed that the presence of nonpermissive HLA-DPB1 mismatches was correlated with significantly increased hazards of acute grade II to IV graft-versus-host disease (HR = 1.87, P =.046) and transplantation-related mortality (HR = 2.69, P = .027) but not relapse (HR = 0.98, P = .939), as compared with the permissive group. There was also a marked but statistically not significant increase in the hazards of overall mortality (HR = 1.64, P = .1). These data suggest that biologic characterization of in vivo alloreactivity can be a tool for definition of clinically relevant nonpermissive HLA mismatches for unrelated HSC transplantation. RI apperley, jane/B-4367-2009

The prevalence of autoantibodies has been reported to be increased in both patients with Turner's syndrome and their parents. We evaluated organ-specific and non-organ-specific autoantibodies in 95 patients, ranging in age from infancy to adulthood, and in most of their parents, in order to determine the characteristics of autoimmune disorders in these families and to relate it to the genetic markers usually involved in autoimmunity (HLA, GM and KM genes). A statistically significant difference was observed between Turner patients and controls in the frequencies of organ-specific autoantibodies, in particular thyroid microsomal antibodies and thyroglobulin antibodies; however, the presence of autoantibodies was not associated with overt diseases in most cases. No significant difference was found between parents and controls. A study of the inheritance of the autoimmunity showed that transmission was preferentially paternal, since Turner patients had more chance of presenting autoantibodies when their fathers had autoantibodies rather than their mothers. A positive association was found between the presence of auto-antibodies and HLA-DR7;DQ2 and HLA-DR7;DQ9 haplotypes in Turner patients and fathers. No significant association was found between GM and KM allotype frequencies in Turner patients and their parents and the presence of autoantibodies. No epistatic interaction was demonstrated between HLA and GM or KM genes. Familial segregation was studied and a preferentially paternal transmission of HLA-DR7-carrying haplotypes and possibly also of the KM (1) allotype with autoimmunity was observed.

The transplantation of two cord blood (CB) units obtained from unrelated donors (double CBT) is an effective strategy for adult patients with hematologic malignancies. Sustained hematopoiesis after double CBT is usually derived from a single donor, and only a few transplantation recipients displaying a stable mixed donor-donor chimerism have been reported. We investigated the mechanisms underlying single-donor predominance in double CBT by studying in vitro the role of the graft-versus-graft cell-mediated immune effect in two-way mixed-lymphocyte culture, along with the contribution of differential hematopoietic progenitor (HP) potency in HP mixed cultures. Results for the two-way mixed-lymphocyte culture showed that despite the weak and variable alloantigen-specific cytotoxic potential displayed by CB mononuclear cells, an immune-mediated dominance for one of the two CB units was detected in the majority of experiments. Alloantigen-induced cytotoxic activity was directed toward both CB-HP and phytohemagglutinin (PHA)-activated T lymphoblastoid cells. The CB unit with the higher fold expansion of CD34(+) cells in single-expansion culture was prevalent in the HP mixed-expansion culture, as shown by DNA chimerism evaluation. Based on these data, we hypothesize that the dominant CB unit is able to develop prevalent cytotoxic activity toward activated lymphocytes of the other CB unit, thereby preventing them from exerting alloantigen-specific cytotoxic potential against both activated lymphocytes and HPs of the dominant unit. In accordance with this hypothesis, we propose the evaluation of alloantigen-induced cytotoxic activity generated in two-way mixed-lymphocyte culture and directed toward PHA-activated T lymphoblastoid cells as a tool to identify the potentially predominant CB unit before double CBT.