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IntroductionCD34 ϩ cell populations in human bone marrow and peripheral blood can act as antigen-presenting cells (APCs) and activate allogeneic T cells in vitro due to the presence of committed myeloid progenitors that constitutively express HLA and adhesion and costimulatory molecules. 1,2 These latter molecules are upregulated on CD34 ϩ cells upon binding to T cells or after addition of tumor necrosis factor-␣ (TNF␣) for 24 hours to the culture. 2,3 Similarly, ICOS-L expression on CD34 ϩ cells can be induced by TNF␣ and can act as an alternative costimulatory pathway on stem cells. 4 Moreover, the expression of costimulatory molecules identifies a subpopulation of CD34 ϩ progenitors that differentiate into dendritic cells (DCs) in liquid culture. 3,5 CD34 ϩ cells from cord blood (CB) also generate myeloid DCs in response to granulocytemacrophage colony-stimulating factor (GM-CSF) and TNF␣ in vitro 6,7 and allow the engraftment of functional DCs in nonobese diabetic-severe combined immunodeficiency (NOD/SCID) mice. 8 After hematopoietic stem cell (HSC) transplantation, allogeneic donor T cells respond to host APCs and initiate graft-versus-host disease (GVHD) but also facilitate the engraftment of donor CD34 ϩ cells. 9,10 Experiments in NOD/SCID mice suggested an important role of CD8 ϩ T cells in facilitating the migration, homing, and engraftment of CD34 ϩ cells through alteration of signaling via the chemokine receptor CXCR4. 11 However, while T cells can enhance the stimulatory activity of DCs, 12 the effect of donor T cells on the APC function of CD34 ϩ cells is not known. Multiple clinical studies have shown direct correlations between CD34 ϩ cell dose [13][14][15][16] and the development of GVHD. Mielcarek et al 17 have hypothesized that donor CD34 ϩ APCs, or APCs derived from CD34 ϩ cells, may contribute to the development of GVHD by indirect presentation of host alloantigen.In this study, we show that allogeneic T cells can affect the function of CD34 ϩ cells by inducing the proliferation and rapid differentiation of a subset of progenitors into monocytic-dendritic precursors capable of both direct and indirect alloantigen presentation. Cotransplantation of CD34 ϩ cells and allogeneic T cells into NOD/SCID mice resulted in a better engraftment of human CD45 ϩ cells with dendritic phenotype than cotransplantation with autologous T cells. Among the mechanisms used by T cells to stimulate CD34 ϩ cell proliferation and differentiation, we describe here both the ligation of cellular receptors and the release of cytokines, such as GM-CSF and TNF␣. Materials and methods Flow cytometryFlow cytometric analysis was performed on samples of peripheral blood (PB) and CB cells. Cell separationCB mononuclear cells (MNCs) were obtained by centrifugation over Ficoll/Hypaque (Amersham Biosciences, Piscataway, NJ) gradients. Lightdensity cells were washed twice in PBS (Cambrex, Walkersville, MD) with 1% bovine serum albumin (BSA; Sigma Chemical, St Louis, MO), and CD34 ϩ cells were purified by MidiMACS high-gradient ma...

PURPOSE: To evaluate the prevalence of immunologic and genetic markers in patients with idiopathic ocular inflammation and a family history of inflammatory bowel disease. DESIGN: Prospective, matched case-control study. METHODS: Patients with a diagnosis of idiopathic ocular inflammation and family history of inflammatory bowel disease (IBD) who did not have IBD themselves were identified and matched to control patients with idiopathic ocular inflammation without a personal or family history of IBD. Serum was evaluated for immunologic markers using Prometheus IBD 7 Serology®. Genomic DNA was analyzed for single nucleotide polymorphisms (SNP) of the NOD2 gene associated with Crohn’s disease. RESULTS: Fifteen patients with idiopathic ocular inflammation and family history of inflammatory bowel disease were matched to fifteen control patients based on age, gender, and race. 8/15 (53%) patients with a family history of IBD had elevated p-ANCA antibody levels compared to 3/15 (20%) of controls (one sided P=0.04) with a matched analysis OR of 6.0 [one-sided P=0.06]. 4/15 (27%) patients with family history of IBD tested positive for immunologic markers predicting ulcerative colitis, while no control patients tested positive [one-sided P=0.06]. Carrier rates of NOD2 SNPs did not differ significantly between the test and control groups. CONCLUSIONS: One quarter of patients with idiopathic ocular inflammation and a family history of inflammatory bowel disease had immunologic markers predicting IBD, and one half had elevated p-ANCA levels. IBD serology may be useful in the evaluation of selected patients with unexplained uveitis.

Cord blood (CB) mononuclear cells (MNCs) can be transplanted in HLA mismatched recipients with limited graft rejection or graft-versus-host disease (GVHD). Previous studies have shown that naive T cells and hyporesponsive dendritic cells are largely represented in CB. Data presented here demonstrate that CB MNCs are unable to stimulate allogeneic T cell proliferative or cytotoxic responses in standard in vitro assays. However, a suppressive effect of CB MNCs was ruled out because purified CD34(+) cells or CD14(+) monocytes stimulated T cell responses that were not inhibited by add-back of CB MNCs. The lack of antigen-presenting cell (APC) activity of CB MNCs in primary mixed lymphocyte culture (MLC) did not induce allogeneic T cell anergy. In fact, rechallenge of T cells with CB CD34(+) cells, or immature monocyte-derived dendritic cells (iMo-DCs) in secondary MLC induced potent T cell proliferative responses. A delayed APC activity of CB MNCs was observed after stimulation with irradiated allogeneic T cells for 6 days, likely because of the upregulation of CD86 and HLA-DR on CB cells. Cytotoxic lymphocytes (CTL) were generated after stimulation of blood T cells with CB MNCs for 4 weeks or CB-derived iMo-DCs for 1 week. Concomitant stimulation of T cells with CB iMo-DC obtained from 2 CB units resulted in the generation of CTLs specific for each CB, independently of the CB:CB cell ratio. These data suggest that the APC activity of CB cells possibly increases posttransplant, and may contribute to delayed graft rejection and/or acute and chronic GVHD.

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