Peripheral CD34 Cells Research Articles

Cerebrospinal fluid viral load, intrathecal immunoactivation, and cerebrospinal fluid monocytic cell count in HIV-1 infection.

To assess the association between cerebrospinal fluid (CSF) viral load, intrathecal immunoactivation, and immunosuppression in HIV-1-infected individuals with no antiretroviral treatment experience a cross-sectional study of stored frozen CSF and plasma samples were conducted. The study population included a total of 120 antiretroviral-naive HIV-1-infected patients, 110 neuroasymptomatic patients, and 10 with neurologic complications. HIV-1 RNA was quantified in cell-free CSF and plasma using polymerase chain reaction (PCR; Roche Amplicor HIV-1 Monitor version 1.5, Roche Diagnostic Systems, Hoffmann-La Roche, Inc., Base, Switzerland). Immunoactivation was measured by CSF-serum IgG index, CSF neopterin concentrations, and CSF monocytic cell count. The CSF HIV-1 RNA load did not differ significantly between patients with or without neurologic complications. In patients without neurologic symptoms, the CSF monocytic cell counts were correlated to the CSF viral load (r(s) = 0.40, p < .001), whereas IgG index and CSF neopterin concentrations were correlated to the viral load only in the subgroup of patients with CD4 counts > or =200 x 10(6) cells/L. In this subgroup of patients, the peripheral CD4 cell count was, as expected, inversely correlated to the CSF viral load (r. = -0.36, p < .01), whereas in patients with CD4 counts <200 x 10(6) cells/L, an unexpected, significant positive correlation (r(s) = 0.43, p < .01 ) was found. In HIV-1-infected patients with neurologic complications, no significant correlations were found between immune activation, CSF viral load, and immunosuppression.

DIFFERENTIAL EFFECTS OF CD4 AND CD8 CELLS ON APOPTOSIS IN SMALL INTESTINAL TRANSPLANTATION

436 The requirement for allospecific CD4 and CD8 T cells in solid organ graft rejection remains controversial. It was previously demonstrated that CD8 T cells are not necessary for allograft rejection nor the induction of graft cell apoptosis in a high-responder model of small intestinal transplantation(ACI?Lewis). In this study we used the same model to ask whether CD4 cells are required for rejection or apoptosis. Recipient rats were treated withαCD4 mAbs (OX-38), which resulted in the depletion of >85% of CD4+ cells, or a combination of αCD8 mAbs (OX-8) and αCD4 mAbs which depleted >98% of CD8+ cells and >85% of the CD4+ cells. Graft rejection was ameliorated by treatment with αCD4 mAbs while a combination ofαCD4 and αCD8 mAbs abrogated rejection. Furthermore, there was a decrease in the number of apoptotic graft epithelial cells in the CD4-diminished group and a significant decrease (p<.05) in the CD4/CD8 diminished group (Table, column 3). These studies indicate that CD4 cells, but not CD8 cells, are essential for allograft rejection. To examine specific pathways of apoptosis, lysates of allograft tissue were analyzed by Western blot. The levels of FasL protein in the CD8-depleted group were increased relative to the control and CD4-diminished groups. Comparable levels of Bcl-x were detected in all groups. Conversely, message for granzyme B, as determined by competitive RT-PCR, was decreased in the CD8-depleted, and CD4/CD8 diminished groups, as compared to the CD4-diminished group. These data suggest that, in the absence of CD8 cells, CD4 T cells can induce apoptosis of graft cells and that apoptosis may be predominantly Fas-mediated.Interestingly, there was a significant increase in the numbers of apoptotic graft infiltrating cells when peripheral CD4 cells were reduced in allograft recipients (CD4 and CD4/8-diminished groups)(Table, column 4, CD4-and CD4/CD8 diminished vs. control or CD8-depleted, p<.05). Further studies will determine how CD4 T cells regulate apoptosis in allografts. Thus, although apoptosis contributes to tissue damage during allograft rejection, under certain conditions graft infiltrating cells may be deleted by apoptosis.

DIFFERENTIAL EFFECTS OF CD4 AND CD8 CELLS ON APOPTOSIS IN SMALL INTESTINAL TRANSPLANTATION

436 The requirement for allospecific CD4 and CD8 T cells in solid organ graft rejection remains controversial. It was previously demonstrated that CD8 T cells are not necessary for allograft rejection nor the induction of graft cell apoptosis in a high-responder model of small intestinal transplantation(ACI--->Lewis). In this study we used the same model to ask whether CD4 cells are required for rejection or apoptosis. Recipient rats were treated with αCD4 mAbs (OX-38), which resulted in the depletion of >85% of CD4+ cells, or a combination of αCD8 mAbs (OX-8) and αCD4 mAbs which depleted >98% of CD8+ cells and >85% of the CD4+ cells. Graft rejection was ameliorated by treatment with αCD4 mAbs while a combination of αCD4 and αCD8 mAbs abrogated rejection. Furthermore, there was a decrease in the number of apoptotic graft epithelial cells in the CD4-diminished group and a significant decrease (p<.05) in the CD4/CD8 diminished group (Table, column 3).These studies indicate that CD4 cells, but not CD8 cells, are essential for allograft rejection. To examine specific pathways of apoptosis, lysates of allograft tissue were analyzed by Western blot. The levels of FasL protein in the CD8-depleted group were increased relative to the control and CD4-diminished groups. Comparable levels of Bcl-x were detected in all groups. Conversely, message for granzyme B, as determined by competitive RT-PCR, was decreased in the CD8-depleted, and CD4/CD8 diminished groups, as compared to the CD4-diminished group. These data suggest that, in the absence of CD8 cells, CD4 T cells can induce apoptosis of graft cells and that apoptosis may be predominantly Fas-mediated. Interestingly, there was a significant increase in the numbers of apoptotic graft infiltrating cells when peripheral CD4 cells were reduced in allograft recipients (CD4 and CD4/8-diminished groups) (Table, column 4, CD4-and CD4/CD8 diminished vs. control or CD8-depleted, p<.05). Further studies will determine how CD4 T cells regulate apoptosis in allografts. Thus, although apoptosis contributes to tissue damage during allograft rejection, under certain conditions graft infiltrating cells may be deleted by apoptosis.

Constraints on CD4 Recovery Postchemotherapy in Adults: Thymic Insufficiency and Apoptotic Decline of Expanded Peripheral CD4 Cells

AbstractTo examine the mechanisms of CD4 reconstitution in an adult population, lymphocyte repopulation was assessed following dose-intense chemotherapy in 25 breast cancer patients, ages 33 to 69 years. Chemotherapy resulted in a greater than 60% reduction in total CD4 T cells and, in particular, a greater than 90% loss of the CD45RA+ CD4 cells. CD4 recovery was protracted, achieving less than 50% of pretreatment levels after 12 to 14 months. Two facets of the CD4 recovery were notable. First, generation of CD45RA+ CD4 cells played only a minor role in the first year, suggesting that thymic production was not the main route of CD4 regeneration. Indeed, recovery of CD45RA+ CD4 cell levels remained limited in half of the patients even after 2 years. Second, expansion of the mature peripheral CD4 cells (CD45RO+) remaining after chemotherapy was the main source of early CD4 repopulation, peaking at 3 to 6 months postchemotherapy. This expansion was limited in duration, however, and was followed by a secondary decline, such that the total CD45RO+ CD4 levels at 9 to 12 months were lower than at 6 months. When stimulated by mitogens, an increased susceptibility to apoptosis was observed in postchemotherapy CD4 cells as compared with those from normal donors. The elevated expression of markers such as HLA-DR during chemotherapy and for several months postchemotherapy is consistent with the presence of an activated T-cell population. CD4 apoptotic frequency correlated with the frequency of HLA-DR expression on T cells. Thus, CD4 recovery is constrained in adults by a limited thymic regenerative capacity and by an increased susceptibility to apoptosis within the expanding peripheral CD4 population.

Factors associated with increased levels of human immunodeficiency virus type 1 DNA in semen.

Human immunodeficiency virus type 1 (HIV-1)-infected cells have been isolated from semen and may be a major source of transmissible virus. Quantitative polymerase chain reaction (PCR) assay was used to determine HIV proviral DNA load in cellular fractions of semen from 74 antiviral therapy-naive HIV-1-seropositive men and 53 paired blood samples. HIV-1 DNA was detected in 65% of semen (range: <10-5000 copies/mL) and 100% of blood samples (range: 20-2500 copies/mL). HIV-1 DNA copy numbers in semen correlated significantly with those in blood, but for most cases, the concentration of blood HIV-1 DNA was higher (mean blood-to-semen ratio = 2.9). Factors associated with elevated HIV-1 provirus levels in semen included reduced peripheral CD4 cell count and asymptomatic genital tract inflammation (>10(6) white blood cells/mL of semen). These data provide evidence that genital tract inflammation and reduced peripheral CD4 cell count may be associated with enhanced sexual transmission of HIV-1 because of increased numbers of HIV-1-infected cells in semen.

The prevalence of skin disease in HIV infection and its relationship to the degree of immunosuppression.

A cross-sectional study of human immunodeficiency virus (HIV) positive patients who attended the HIV clinic in Brighton over a 4-month period was carried out to describe the prevalence and severity of skin manifestations in HIV-positive patients and to elucidate their association with the peripheral CD4 cell count and with the HIV disease stage. The subjects were consecutively examined by an experienced dermatologist. Skin manifestations were classified into infections, dermatoses, pruritus and neoplasm. A severity index was derived by scoring each condition as either absent, mild, moderate or severe. One hundred and fifty-one patients were enrolled with a mean age of 38.3 years. One hundred and thirty-nine were homo/bisexual men; 58 were asymptomatic and 35 had acquired immune deficiency syndrome (AIDS); 37 had CD4 counts below 200. Skin conditions were present in 138 of the 151 subjects (91.4%). The total number of events was 331. The most frequent problem was infection followed by dermatoses, pruritus and malignancy. The most frequent condition was seborrhoeic eczema followed by tinea and xerosis. We have demonstrated a statistically significant association between CD4 count, disease stage and skin manifestations in HIV-positive individuals.

Peripheral Blood from Human Immunodeficiency Virus Type 1‐Infected Patients Displays Diminished T Cell Generation Capacity

An organ culture chimera system was used to assess the effect of human immunodeficiency virus type 1 (HIV-1) infection on the T cell-generation capacity of precursors derived from human peripheral blood. Peripheral blood mononuclear cells from HIV-1-infected patients and uninfected controls were placed on fetal thymus lobes of NOD/LtSz-scid/scid mice. Blood from the HIV-1-infected patients consistently produced fewer CD4 and CD8 cells compared with blood from controls (P < .01). Addition of zidovudine to the cultures did not alter this profile. Limit dilution experiments suggested that there were fewer functional precursors in the infected patients. These results were not dependent on the patient's level of peripheral CD4 cells; even samples from patients with normal CD4 cell counts were unable to generate T cells in organ cultures. The results are consistent with a loss in the capacity of HIV-1-infected patients to produce functional T cell progenitors in their peripheral blood.

A Range of CD4 T Cell Tolerance: Partial Inactivation to Organ-Specific Antigen Allows Nondestructive Thyroiditis or Insulitis

T cell receptor (TCR) transgenic mice specific for hen egg lysozyme (HEL) were crossed with mice expressing HEL on the thyroid epithelium, on pancreatic islet β cells, or systemically. Depending on the pattern of HEL expression, deletion of double-positive thymocytes ranged from minimal to complete, and peripheral CD4 cells exhibited graded reduction in TCR expression, in vitro responsiveness, and in vivo helper ability. CD4 cells were least tolerant in TCR/thyroid-HEL and TCR/islet-HEL mice, which developed an extensive lymphocytic thyroiditis or insulitis that nevertheless did not eliminate HEL-expressing endocrine cells. Autoreactive CD4 clones thus escape the thymus under a range of circumstances, retain sufficient function to initiate subclinical autoimmune inflammation when self-antigens are concentrated in the thyroid or pancreas, and may regulate progression of subclinical inflammation to destructive autoimmune disease.

CD4 and CD8 expressions in African green monkey helper T lymphocytes: implication for resistance to SIV infection.

We found that most peripheral CD4 cells co-express a low density of CD8 alpha antigen in African green monkeys (AGM). Further, the cell surface expression of CD4 and the expression of CD4 mRNA underwent a decrease when purified CD4CD8low cells were cultured with mitogen and IL-2. These observations suggest that AGM CD4 cells are subject to loss of CD4 expression after lymphocyte activation. Part of the peripheral CD8 fraction exhibited a significant helper activity which suggested the phenotypic conversion in helper T cells from CD4+ to CD4- in vivo. Simian immunodeficiency virus (SIV) grew well in CD4 panning cells following SIV infection. In contrast, CD4CD8low cells were resistant to SIV infection after their conversion to CD4- cells.

Effects of Inhalative Exposure to Dioxins in Wood Preservatives on Cell-Mediated Immunity in Day-Care Center Teachers

The study investigated the effects of chronic inhalative low-level exposure to dioxins in day-care centers containing wood treated with preservatives on (1) the number of peripheral CD4 and CDS cells and the CD4:CD8 ratio in peripheral blood and (2) the delayed-type hypersensitivity reaction of the skin (Multitest Mérieux). The study population consisted of 221 exposed and 189 unexposed employees of day-care centers in or near Hamburg. A status of decreased skin test reagibility was operationalized as hypoergy I (score <5 mm), hypoergy II (≤ 1 positive reaction), and anergy (no positive reaction). Taking the fading during postexposure time into account, a surrogate for the dioxin burden based on the concentration of dioxins in indoor air (measured using the 2,3,7,8-TCDD TEF followed by the Federal Republic of Germany) was modeled. No effect was found regarding the number of CD4 cells, CD8 cells, and CD4:CD8 ratio. However, some evidence for an increasing dose-response relationship between inhalative exposure to dioxins and the risk of hypoergy and anergy was found, both in the total study population and among subjects with a short postexposure time (≤ 6 months). Subjects with a short postexposure time and a dioxin burden >0.6 pg/m 3 had a significantly higher risk of hypoergy than unexposed subjects (hypoergy I: OR = 9.51, 95% CI = 1.9-42.02; hypoergy II: OR = 2.92, 95% CI = 1.14-7.5). It is concluded that a suppressive effect of inhalative exposure to dioxins in wood preservatives on human cell-mediated immunity cannot be ruled out.

T cell activation through Thy-1 is associated with the expression of a surface protein (p100) on a subset of CD4 cells.

Thy-1 molecules, which lack a transmembrane domain, can nonetheless induce T cell activation; it has thus been suggested that a separate transmembrane molecule associated with Thy-1 is required for signal transduction. We have previously characterized a transmembrane protein with an Mr of 100,000 (p100), which is non-covalently bound to two glycosyl-phosphatidylinositol (GPI)-linked molecules, Thy-1 and ThB. p100 is selectively expressed on the T cell surface and divides peripheral CD4 cells into two subpopulations. This differential expression on CD4 cells allowed us to investigate the role of p100 in signal transduction through Thy-1 molecules. Here we report that only p100+ CD4 cells proliferate and release cytokines in response to cross-linkage of Thy-1, although both p100+ and p100- CD4 cells strongly express Thy-1 on their surfaces. Control stimulation by anti-CD3 antibodies or concanavalin A induces identical thymidine uptake by the two CD4 cell populations. Interestingly, these two populations of CD4 cells had different cytokine release profiles after activation through CD3: only p100+ CD4 cells released high amounts of IL-2 and IFN-gamma, whereas both populations released IL-4. p100 expression correlates with the induction of homotypic aggregation of T cells after Thy-1 triggering. p100 is associated with kinase activity (fyn and lck), and phosphorylated proteins of 90, 59, 57 and 33 kDa co-precipitate with Thy-1 only in p100+ CD4 cells. Altogether, these data suggest that p100 is involved in signal transduction through Thy-1. p100 expression by activated CD4 cells in vivo may be relevant to the proposed function of Thy-1 as an accessory signaling molecule in cell activation.

Expression and function of the interleukin 7 receptor in murine lymphocytes.

A monoclonal antibody, A7R34, that recognizes the high-affinity interleukin 7 receptor (IL-7Ra) and blocks the binding between IL-7 and IL-7Ra has been produced. Cell surface staining with A7R34 demonstrated that IL-7Ra is expressed in both B- and T-cell lineages. In the bone marrow, immature B-lineage cells that do not express surface IgM were IL-7Ra+. In the thymus, IL-7Ra was detected in CD4-8- T cells and also in CD4 or CD8 single-positive cells but not in CD4+8+ double-positive cells. In the peripheral lymphoid tissues, both CD4 and CD8 single-positive cells were the major cell types that express IL-7Ra. Addition of A7R34 to a long-term B-precursor-cell culture inhibited proliferation of the B-lineage cells, indicating that IL-7 is an absolute requirement for in vitro B-cell genesis. Consistent with this in vitro result, continuous injection of A7R34 into an adult mouse resulted in a decrease of B-precursor cells and also of thymocytes, whereas a considerable fraction of mature B and T cells in the peripheral tissues persisted over 2 weeks of the experiment. When A7R34 injection is started from day 14 of gestation, it is possible to produce mice that lack B cells. These results indicate that IL-7 is an essential molecule for generation of both B and T cells in murine bone marrow and thymus, respectively. Moreover, IL-7Ra would be the sole receptor system regulating these processes.

A Case of Myasthenia Gravis Associated with Increased Peripheral CD8 Cells and High Activities of Anti-lymphocyte Antibody : Clinical Trial of Immunoadsorption Therapy with Good Response

A Case of Myasthenia Gravis Associated with Increased Peripheral CD8 Cells and High Activities of Anti-lymphocyte Antibody : Clinical Trial of Immunoadsorption Therapy with Good Response