Target lesion calcification in coronary artery disease: an intravascular ultrasound study.

OBJECTIVES. The purpose of this study was to evaluate the frequency, amount and distribution of target lesion calcification in patients undergoing transcatheter therapy for symptomatic coronary artery disease. BACKGROUND. Coronary artery target lesion calcification may be an important determinant of response to transcatheter therapy: balloon angioplasty causes dissections in calcified lesions, directional atherectomy cuts calcium poorly, rotational atherectomy causes preferential ablation of calcium and laser irradiation effect may vary. Intravascular ultrasound imaging is a highly sensitive technique for detection of plaque calcification in vivo. METHODS. We performed intravascular ultrasound imaging before or after, or both, various transcatheter therapies in 110 patients. These 84 men and 26 women had a mean age of 60 years and a duration of angina of 22 +/- 34 months. Forty-nine patients had one-vessel, 29 had two-vessel, 25 had three-vessel and 7 had left main coronary disease. Vessels treated and imaged were the left main (n = 7), left anterior descending (n = 47), left circumflex (n = 18) and right (n = 38) coronary arteries. RESULTS. Eighty-four patients (76%) had target lesion calcification; 29 patients had one-quadrant, 25 had two-quadrant, 17 had three-quadrant and 13 had four-quadrant calcification. The calcification was superficial in 42 patients, deep in 13 and both superficial and deep in 31. The axial length of calcium could be measured in 29 patients; it was < or = 5 mm in 11 and > or = 6 mm in 18. Fluoroscopy detected calcification in 50 patients (48%, p < 0.001 vs. detection by ultrasound); this proportion increased to 74% in patients with calcification of two or more quadrants and to 86% in patients with calcification > or = 6 mm in length of two or more quadrants. Calcification was more common in patients who smoked and tended to be more common in patients with multivessel disease or previous coronary artery bypass graft surgery. CONCLUSIONS. We conclude that target lesion calcification occurs in 75% of patients with symptomatic coronary artery disease requiring angioplasty. Target lesion calcification is best detected, localized and quantified by intravascular ultrasound. These observations may be important in selecting devices for transcatheter therapy.     

Characterization of subsets of CD4+ memory T cells reveals early branched pathways of T cell differentiation in humans

The pathways for differentiation of human CD4(+) T cells into functionally distinct subsets of memory cells in vivo are unknown. The identification of these subsets and pathways has clear implications for the design of vaccines and immune-targeted therapies. Here, we show that populations of apparently naive CD4(+) T cells express the chemokine receptors CXCR3 or CCR4 and demonstrate patterns of gene expression and functional responses characteristic of memory cells. The proliferation history and T cell receptor repertoire of these chemokine-receptor(+) cells suggest that they are very early memory CD4(+) T cells that have "rested down" before acquiring the phenotypes described for "central" or "effector" memory T cells. In addition, the chemokine-receptor(+) "naive" populations contain Th1 and Th2 cells, respectively, demonstrating that Th1/Th2 differentiation can occur very early in vivo in the absence of markers conventionally associated with memory cells. We localized ligands for CXCR3 and CCR4 to separate foci in T cell zones of tonsil, suggesting that the chemokine-receptor(+) subsets may be recruited and contribute to segregated, polarized microenvironments within lymphoid organs. Importantly, our data suggest that CD4(+) T cells do not differentiate according to a simple schema from naive --> CD45RO(+) noneffector/central memory --> effector/effector memory cells. Rather, developmental pathways branch early on to yield effector/memory populations that are highly heterogeneous and multifunctional and have the potential to become stable resting cells.     

Effects of exogenous interleukin-7 on human thymus function

Immune reconstitution is a critical component of recovery after treatment of human immunodeficiency virus (HIV) infection, cancer chemotherapy, and hematopoietic stem cell transplantation. The ability to enhance T-cell production would benefit such treatment. We examined the effects of exogenous interleukin-7 (IL-7) on apoptosis, proliferation, and the generation of T-cell receptor rearrangement excision circles (TRECs) in human thymus. Quantitative polymerase chain reaction demonstrated that the highest level of TRECs (14 692 copies/10 000 cells) was present in the CD1a(+)CD3(-)CD4(+)CD8(+) stage in native thymus, suggesting that TREC generation occurred following the cellular division in this subpopulation. In a thymic organ culture system, exogenous IL-7 increased the TREC frequency in fetal as well as infant thymus, indicating increased T-cell receptor (TCR) rearrangement. Although this increase could be due to the effect of IL-7 to increase thymocyte proliferation and decrease apoptosis of immature CD3(-) cells, the in vivo experiments using NOD/LtSz-scid mice given transplants of human fetal thymus and liver suggested that IL-7 can also directly enhance TREC generation. Our results provide compelling evidence that IL-7 has a direct effect on increasing TCR-alphabeta rearrangement and indicate the potential use of IL-7 for enhancing de novo na?ve T-cell generation in immunocompromised patients.     

Surface expression patterns of negative regulatory molecules identify determinants of virus-specific CD8+ T-cell exhaustion in HIV infection

A highly complex network of coinhibitory and costimulatory receptors regulates the outcome of virus-specific CD8(+) T-cell responses. Here, we report on the expression patterns of multiple inhibitory receptors on HIV-specific, cytomegalovirus-specific, and bulk CD8(+) T-cell memory populations. In contrast to cytomegalovirus-specific CD8(+) T cells, the majority of HIV-specific CD8(+) T cells exhibited an immature phenotype and expressed Programmed Death-1, CD160 and 2B4 but not lymphocyte activation gene-3. Notably, before antiretroviral therapy, simultaneous expression of these negative regulators correlated strongly with both HIV load and impaired cytokine production. Suppression of HIV replication by antiretroviral therapy was associated with reduced surface expression of inhibitory molecules on HIV-specific CD8(+) T cells. Furthermore, in vitro manipulation of Programmed Death-1 and 2B4 inhibitory pathways increased the proliferative capacity of HIV-specific CD8(+) T cells. Thus, multiple coinhibitory receptors can affect the development of HIV-specific CD8(+) T-cell responses and, by extension, represent potential targets for new immune-based interventions in HIV-infected persons.     

Superior control of HIV-1 replication by CD8+ T cells is reflected by their avidity, polyfunctionality, and clonal turnover

The key attributes of CD8+ T cell protective immunity in human immunodeficiency virus (HIV) infection remain unclear. We report that CD8+ T cell responses specific for Gag and, in particular, the immunodominant p24 epitope KK10 correlate with control of HIV-1 replication in human histocompatibility leukocyte antigen (HLA)-B27 patients. To understand further the nature of CD8+ T cell-mediated antiviral efficacy, we performed a comprehensive study of CD8+ T cells specific for the HLA-B27-restricted epitope KK10 in chronic HIV-1 infection based on the use of multiparametric flow cytometry together with molecular clonotypic analysis and viral sequencing. We show that B27-KK10-specific CD8+ T cells are characterized by polyfunctional capabilities, increased clonal turnover, and superior functional avidity. Such attributes are interlinked and constitute the basis for effective control of HIV-1 replication. These data on the features of effective CD8+ T cells in HIV infection may aid in the development of successful T cell vaccines.     

Progressive CD4+ central memory T cell decline results in CD4+ effector memory insufficiency and overt disease in chronic SIV infection

Primary simian immunodeficiency virus (SIV) infections of rhesus macaques result in the dramatic depletion of CD4(+) CCR5(+) effector-memory T (T(EM)) cells from extra-lymphoid effector sites, but in most infections, an increased rate of CD4(+) memory T cell proliferation appears to prevent collapse of effector site CD4(+) T(EM) cell populations and acute-phase AIDS. Eventually, persistent SIV replication results in chronic-phase AIDS, but the responsible mechanisms remain controversial. Here, we demonstrate that in the chronic phase of progressive SIV infection, effector site CD4(+) T(EM) cell populations manifest a slow, continuous decline, and that the degree of this depletion remains a highly significant correlate of late-onset AIDS. We further show that due to persistent immune activation, effector site CD4(+) T(EM) cells are predominantly short-lived, and that their homeostasis is strikingly dependent on the production of new CD4(+) T(EM) cells from central-memory T (T(CM)) cell precursors. The instability of effector site CD4(+) T(EM) cell populations over time was not explained by increasing destruction of these cells, but rather was attributable to progressive reduction in their production, secondary to decreasing numbers of CCR5(-) CD4(+) T(CM) cells. These data suggest that although CD4(+) T(EM) cell depletion is a proximate mechanism of immunodeficiency, the tempo of this depletion and the timing of disease onset are largely determined by destruction, failing production, and gradual decline of CD4(+) T(CM) cells.     

Delay of T cell senescence by caloric restriction in aged long-lived nonhuman primates

Caloric restriction (CR) has long been known to increase median and maximal lifespans and to decreases mortality and morbidity in short-lived animal models, likely by altering fundamental biological processes that regulate aging and longevity. In rodents, CR was reported to delay the aging of the immune system (immune senescence), which is believed to be largely responsible for a dramatic increase in age-related susceptibility to infectious diseases. However, it is unclear whether CR can exert similar effects in long-lived organisms. Previous studies involving 2- to 4-year CR treatment of long-lived primates failed to find a CR effect or reported effects on the immune system opposite to those seen in CR-treated rodents. Here we show that long-term CR delays the adverse effects of aging on nonhuman primate T cells. CR effected a marked improvement in the maintenance and/or production of na?ve T cells and the consequent preservation of T cell receptor repertoire diversity. Furthermore, CR also improved T cell function and reduced production of inflammatory cytokines by memory T cells. Our results provide evidence that CR can delay immune senescence in nonhuman primates, potentially contributing to an extended lifespan by reducing susceptibility to infectious disease.     

Functional leukemia-associated antigen-specific memory CD8+ T cells exist in healthy individuals and in patients with chronic myelogenous leukemia before and after stem cell transplantation

Antigens implicated in the graft-versus-leukemia (GVL) effect in chronic myeloid leukemia (CML) include WT1, PR1, and BCR-ABL. To detect very low frequencies of these antigen-specific CD8+ T cells, we used quantitative polymerase chain reaction (qPCR) to measure interferon-gamma (IFN-gamma) mRNA production by peptide-pulsed CD8+ T cells from HLA-A*0201+ healthy volunteers and from patients with CML before and after allogeneic stem cell transplantation (SCT). Parallel assays using cytomegalovirus (CMV) pp65 tetramers demonstrated the IFN-gamma copy number to be linearly related to the frequency of tetramer-binding T cells, sensitive to frequencies of 1 responding CD8+ T cell/100 000 CD8+ T cells. Responses to WT1 and PR1 but not BCR-ABL were detected in 10 of 18 healthy donors. Responses to WT1, PR1, or BCR-ABL were observed in 9 of 14 patients with CML before SCT and 5 of 6 after SCT, often to multiple epitopes. Responses were higher in patients with CML compared with healthy donors and highest after SCT. These antigen-specific CD8+ T cells comprised central memory (CD45RO+CD27+CD57-) and effector memory (CD45RO-CD27-CD57+) T cells. In conclusion, leukemia-reactive CD8+ T cells derive from memory T cells and occur at low frequencies in healthy individuals and at higher frequencies in patients with CML. The increased response in patients after SCT suggests a quantitative explanation for the greater effect of allogeneic SCT.     

A broad T-cell repertoire diversity and an efficient thymic function indicate a favorable long-term immune reconstitution after cord blood stem cell transplantation

Cord blood (CB) is used increasingly as a source of hematopoietic stem cells because of a lower risk of acute and chronic graft-versus-host disease (GVHD). However, there is some concern regarding the ability to adequately reconstitute host immune response due to the immaturity and naivety of CB T cells. This study was designed to evaluate T-cell reconstitution using combined approaches of phenotyping, analysis of alphabeta T-cell receptor (TCR) diversity, and assessment of ex vivo thymic function by measuring TCR rearrangement excision circles (TRECs). Ten patients who underwent CB transplantation for high-risk hematologic disorders were compared to a reference group of 19 age- and GVHD-matched patients who underwent transplantation with non-T cell-depleted bone marrow from an HLA-identical sibling donor. TREC values correlated with the relative number of naive T cells and with TCR repertoire polyclonality. During the first year after transplantation, TCR repertoires were highly abnormal and TREC values low in both groups. Notably, 2 years after transplantation onward TREC values as well as TCR diversity were higher in CB recipients than in recipients of bone marrow transplants. These data indicate an efficient thymic regeneration pathway from CB lymphoid progenitors despite the low number of cells infused compared to bone marrow, arguing for a complete clinical immune recovery after CB transplantation.