ABSTRACT
T suppressor and regulatory cells have been shown to play an important role in the maintenance of central and peripheral tolerance thereby preventing allograft rejection, autoimmunity and allergy. We have previously described a distinct population of antigen-specific CD8(+)CD28(-) T suppressor cells (T(S)). These CD8(+)CD28(-) T(S) cells can be generated in vitro after multiple rounds of stimulation of human peripheral blood mononuclear cells (PBMCs) with either allogenic- or xenogeneic-donor APCs. CD8(+)CD28(-) T(S) cells are FOXP3+, MHC class I-restricted and tolerize both professional antigen presenting cells, such as dendritic cells (DC) and nonprofessional APC such as endothelial cells (EC) by up-regulating the cell surface expression of inhibitory receptors immunoglobulin-like transcript (ILT)-3 and ILT4 and down-regulating the expression of costimulatory molecules such as CD58 and CD86. Tolerized ILT3(high), ILT4(high) APC anergize CD4(+) T(H) cells and can induce the generation of antigen-specific CD4(+)CD25(+) T regulatory cells (T(R)) cells and CD8(+)CD28(-) T(S) cells. In this review, we present our recent studies on the molecular characterization of these antigen specific T suppressor cells and tolerogenic APC.
Subject(s)
Dendritic Cells , Gene Expression Profiling , T-Lymphocyte Subsets , T-Lymphocytes, Regulatory , Cell Line , Endothelial Cells/immunology , Humans , Immune Tolerance , Oligonucleotide Array Sequence AnalysisABSTRACT
Hematopoietic stem cell (HSC) transplantation is an important therapeutic option for patients with hematologic malignancies. To explore the immunomodulatory effects of HSC mobilization agents, we studied the function and phenotype of CD4(+) T cells from 16 adult patients with hematologic malignancies undergoing HSC mobilization treatment for autologous transplantation. Immune cell function was determined using the Immuknow (Cylex) assay by measuring the amount of adenosine triphosphate (ATP) produced by CD4(+) cells from whole blood. ATP activity measured in G-CSF-treated patients was significantly higher than that measured in healthy individuals or "nonmobilized" patients. In patients treated with G-CSF, CD4(+) T cells were predominantly CD25(low)FOXP3(low), consistent with an activated phenotype. However, T-cell depletion did not abrogate ATP production in blood samples from G-CSF-treated patients, indicating that CD4(+) myeloid cells contributed to the increased ATP levels observed in these patients. There was a significant correlation between ATP activity and patient survival, suggesting that efficient activation of CD4(+) cells during mobilization treatment predicts a low risk of disease relapse. Monitoring immune cell reactivity using the Immuknow assay may assist in the clinical management of patients with hematologic malignancies and optimization of HSC mobilization protocols.
Subject(s)
Adenosine Triphosphate/biosynthesis , CD4-Positive T-Lymphocytes/metabolism , Colony-Stimulating Factors/therapeutic use , Hematologic Neoplasms/therapy , Hematopoietic Stem Cell Mobilization , CD4-Positive T-Lymphocytes/drug effects , Colony-Stimulating Factors/pharmacology , Female , Forkhead Transcription Factors/metabolism , Granulocyte Colony-Stimulating Factor/pharmacology , Granulocyte Colony-Stimulating Factor/therapeutic use , Granulocyte-Macrophage Colony-Stimulating Factor/pharmacology , Granulocyte-Macrophage Colony-Stimulating Factor/therapeutic use , Hematologic Neoplasms/drug therapy , Hematologic Neoplasms/metabolism , Humans , Interleukin-2 Receptor alpha Subunit/metabolism , Kaplan-Meier Estimate , Leukocyte Count , Lymphocyte Activation/drug effects , Lymphocyte Depletion , Male , Middle Aged , Phytohemagglutinins/pharmacology , ROC Curve , Sex Characteristics , Stem Cells/cytologySubject(s)
Endothelial Cells/immunology , Endothelium, Vascular/immunology , Immune Tolerance/immunology , Receptors, Cell Surface/immunology , Receptors, Immunologic/immunology , T-Lymphocyte Subsets/immunology , T-Lymphocytes, Regulatory/immunology , Transplantation, Homologous/immunology , Animals , DNA-Binding Proteins/physiology , Forkhead Transcription Factors , Humans , Immunity, Cellular , Isoantigens/immunology , Lymphocyte Activation , Membrane Glycoproteins , Models, Immunological , RodentiaABSTRACT
Monitoring of immune status in transplant recipients is essential for predicting the risk of rejection or infection. In this study, we assessed the significance of immune cell function in 76 renal allograft recipients after Thymoglobulin induction and initiation of maintenance immunosuppression. Using the Immuknow (Cylex Inc) assay, the amount of adenosine triphosphate (ATP) produced by CD4+ cells in response to phytohemagglutinin (PHA) was measured in patients whole blood. In parallel, the frequency and phenotype of CD4+ T cells were determined by flow cytometry. The Immuknow assay yielded paradoxically high ATP values during the first 3 months post-transplantation, despite very low CD4+ T cell counts. High ATP values were caused by peripheral blood myeloid cells, did not predict rejection, and occurred primarily in transplant recipients who received darbepoietin (p = 0.017). CD4+ T cells displayed predominantly an activated/memory phenotype and comprised a subpopulation of CD25+FOXP3+ cells. Over the first 5 months post-transplantation, mean ATP activity gradually decreased, whereas CD4+ T cell counts slowly increased. Low ATP values were predictive of infection (p = 0.002). Thus Immuknow results need to be interpreted with caution in patients receiving Thymoglobulin induction therapy. Although low ATP levels identify patients at increased risk for infection, high ATP values fail to correlate with rejection and do not justify increased immunosuppression.