Combined CD4+ donor lymphocyte infusion and low-dose recombinant IL-2 expand FOXP3+ regulatory T cells following allogeneic hematopoietic stem cell transplantation.

CD4(+)CD25(+)FOXP3(+) regulatory T cells (Treg) successfully control graft-versus-host-disease (GVHD) in animal models. In humans, incomplete reconstitution of Treg after allogeneic hematopoietic stem cell transplantation (HSCT) has been associated with chronic GVHD (cGVHD). Recent studies have demonstrated that interleukin (IL)-2 infusions expand Treg in vivo. However, the effectiveness of this therapy depends on the number of cells capable of responding to IL-2. We examined the effect of low-dose IL-2 infusions on Treg populations after HSCT in patients who also received infusions of donor CD4(+) lymphocytes. Utilizing FOXP3 as a Treg marker, we found that patients who received CD4+DLI concomitantly with IL-2 had greater expansion of Treg compared to patients who received IL-2 (P = .03) or CD4(+)DLI alone (P = .001). FOXP3 expression correlated with absolute CD4(+)CD25(+) cell counts. Moreover, expanded CD4(+)CD25(+) T cells displayed normal suppressive function and treatment with CD4(+)DLI and IL-2 was not associated with GVHD. This study suggests that administration of low-dose IL-2 combined with adoptive CD4(+) cellular therapy may provide a mechanism to expand Treg in vivo.

Erythroid-lineage-specific engraftment in patients with severe hemoglobinopathy following allogeneic hematopoietic stem cell transplantation.

OBJECTIVE: We aimed to create a molecular assay to monitor erythroid (red blood cell [RBC]) engraftment in any patient following allogeneic hematopoietic stem cell transplantation, independent of disease-specific mutations. MATERIALS AND METHODS: We identified 10 common single nucleotide polymorphisms (SNPs), expressed by genes encoding RBC antigens and structural proteins. These SNPs were polymerase chain reaction-amplified from total RNA extracted from peripheral blood, which contains nucleated erythroid progenitors. Mixing studies validated that each SNP can quantitatively measure donor/recipient DNA and RNA. RESULTS: We directly genotyped 23 patients who underwent hematopoietic stem cell transplantation and their human leukocyte antigen-matched donors and found a median of three informative SNPs (i.e., discordant between donor and recipient) per pair. By using the informative RBC SNPs to quantify donor-derived RBC transcripts, we compared rates of RBC engraftment in 13 patients with hemoglobinopathies vs donor mononuclear cell (white blood cell [WBC]) engraftment. Consistent with known ineffective erythropoiesis associated with hemoglobinopathies, we detected up to threefold greater RBC-specific compared to overall WBC engraftment in five of eight patients who were mixed chimeras by transplant day 30. The remaining three of eight who received ABH-incompatible grafts, demonstrated at least 0.5-fold lower RBC compared to WBC engraftment that was related to persistence of host-derived anti-isohemagglutinin antibodies. CONCLUSION: This RNA-based assay can be used to monitor RBC-specific engraftment regardless of a patient's specific hemoglobin mutation or even diagnosis. We propose that panels of expressed SNPs informative for other cell lineages can be created to comprehensively assess the impact of novel stem cell-based therapies on lineage-specific engraftment.

IL-2 regulates FOXP3 expression in human CD4+CD25+ regulatory T cells through a STAT-dependent mechanism and induces the expansion of these cells in vivo.

IL-2 plays a critical role in the maintenance of CD4+CD25+ FOXP3(+) regulatory T cells (Tregs) in vivo. We examined the effects of IL-2 signaling in human Tregs. In vitro, IL-2 selectively up-regulated the expression of FOXP3 in purified CD4+CD25+ T cells but not in CD4+CD25- cells. This regulation involved the binding of STAT3 and STAT5 proteins to a highly conserved STAT-binding site located in the first intron of the FOXP3 gene. We also examined the effects of low-dose IL-2 treatment in 12 patients with metastatic cancer and 9 patients with chronic myelogenous leukemia after allogeneic hematopoietic stem cell transplantation. Overall, IL-2 treatment resulted in a 1.9 median fold increase in the frequency of CD4+CD25+ cells in peripheral blood as well as a 9.7 median fold increase in FOXP3 expression in CD3+ T cells. CD56+CD3- natural killer (NK) cells also expanded during IL-2 therapy but did not express FOXP3. In vitro treatment of NK cells with 5-aza-2'-deoxycytidine restored the IL-2 signaling pathway leading to FOXP3 expression, suggesting that this gene was constitutively repressed by DNA methylation in these cells. Our findings support the clinical evaluation of low-dose IL-2 to selectively modulate CD4+CD25+ Tregs and increase expression of FOXP3 in vivo.

Fas-associated protein with death domain (FADD)-independent recruitment of c-FLIPL to death receptor 5.

Here we show a novel mechanism by which FLICE-like inhibitory protein (c-FLIP) regulates apoptosis induced by tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) and one of its receptors, DR5. c-FLIP is a critical regulator of the TNF family of cytokine receptor signaling. c-FLIP has been postulated to prevent formation of the competent death-inducing signaling complex (DISC) in a ligand-dependent manner, through its interaction with FADD and/or caspase-8. In order to identify regulators of TRAIL function, we used the intracellular death domain (DD) of DR5 as a target to screen a phage-displayed combinatorial peptide library. The DD of DR5 selected from the library a peptide that showed sequence similarity to a stretch of amino acids in the C terminus of c-FLIP(L). The phage-displayed peptide selectively interacted with the DD of DR5 in in vitro binding assays. Similarly, full-length c-FLIP (c-FLIP(L)) and the C-terminal p12 domain of c-FLIP interacted with DR5 both in in vitro pull-down assays and in mammalian cells. This interaction was independent of TRAIL. To the contrary, TRAIL treatment released c-FLIP(L) from DR5, permitting the recruitment of FADD to the active DR5 signaling complex. By employing FADD-deficient Jurkat cells, we demonstrate that DR5 and c-FLIP(L) interact in a FADD-independent manner. Moreover, we show that a cellular membrane permeable version of the peptide corresponding to the DR5 binding domain of c-FLIP induces apoptosis in mammalian cells. Taken together, these findings indicate that c-FLIP interacts with the DD of DR5, thus preventing death (L)signaling by DR5 prior to the formation of an active DISC. Because TRAIL and DR5 are ubiquitously expressed, the interaction of c-FLIP(L) and DR5 indicates a mechanism by which tumor selective apoptosis can be achieved through protecting normal cells from undergoing death receptor-induced apoptosis.

Glutathione S-transferase M null homozygosity and risk of systemic lupus erythematosus associated with sun exposure: a possible gene-environment interaction for autoimmunity.

OBJECTIVE: Multiple genetic factors modulate predisposition to systemic lupus erythematosus (SLE). The glutathione S-transferase (GST) genes GSTM1, GSTT1, and GSTP1 catalyze metabolic pathways for the excretion of reactive oxygen species that may be generated by cellular oxidative stress induced by ultraviolet radiation in sunlight. We hypothesized that risk of SLE associated with occupational sun exposure is modulated by GSTM1, GSTT1, and GSTP1 genotypes. METHODS: DNA samples and occupational history were collected from 243 cases and 298 controls in the Carolina Lupus Study, a population based case-control study of patients with recently diagnosed SLE. RESULTS: There was no independent association between SLE and presence of the homozygous null GSTM1 or GSTT1 genotype, the homozygous Val/Val or heterozygous Val/Ile GSTP1 genotype, or occupational sunlight exposure. The prevalence of Ro autoantibodies was significantly increased among Caucasians with the GSTM1 null genotype (OR 2.6, 95% CI 1.0, 6.8), but was somewhat weaker among African-Americans (OR 1.5, 95% CI 0.7, 3.5). In the combined analysis of occupational sunlight exposure and GSTM1 genotype, the effect of sun exposure among Caucasians varied depending on GSTM1 genotype. There was a 3-fold increased risk (OR 3.1, 95% CI 0.9, 10.8) of SLE associated with 24 or more months' occupational sun exposure among Caucasians with the GSTM1 null genotype, but sun exposure was not associated with risk among GSTM1 positive Caucasians (OR 0.6, 95% CI 0.3, 1.5). The interaction was statistically significant (p = 0.028). CONCLUSION: Our results suggest that GSTM1 homozygous null genotype may modify the effect of occupational sun exposure on the risk of SLE in caucasians.