Defective T-cell response to PHA and mitogenic monoclonal antibodies in male homosexuals with acquired immunodeficiency syndrome and its in vitro correction by interleukin 2

Lactate inhibits naked mole-rat cardiac mitochondrial respiration

In aerobic conditions, the proton-motive force drives oxidative phosphorylation (OXPHOS) and the conversion of ADP to ATP. In hypoxic environments, OXPHOS is impaired, resulting in energy shortfalls and the accumulation of protons and lactate. This results in cellular acidification, which may impact the activity and/or integrity of mitochondrial enzymes and in turn negatively impact mitochondrial respiration and thus aerobic ATP production. Naked mole-rats (NMRs) are among the most hypoxia-tolerant mammals and putatively experience intermittent hypoxia in their underground burrows. However, if and how NMR cardiac mitochondria are impacted by lactate accumulation in hypoxia is unknown. We predicted that lactate alters mitochondrial respiration in NMR cardiac muscle. To test this, we used high-resolution respirometry to measure mitochondrial respiration in permeabilized cardiac muscle fibres from NMRs exposed to 4 h of in vivo normoxia (21% O₂) or hypoxia (7% O₂). We found that: (1) cardiac mitochondria cannot directly oxidize lactate, but surprisingly, (2) lactate inhibits mitochondrial respiration, and (3) decreases complex IV maximum respiratory capacity. Finally, (4) in vivo hypoxic exposure decreases the magnitude of lactate-mediated inhibition of mitochondrial respiration. Taken together, our results suggest that lactate may retard electron transport system function in NMR cardiac mitochondria, particularly in normoxia, and that NMR hearts may be primed for anaerobic metabolism.

Diminished Production of Interleukin 2 and Gamma-Interferon by Cloned «T» Cells from Patients with the Acquired Immunodeficiency Syndrome (AIDS)

A total of 76 T-cell clones established from peripheral blood (PB) of 2 patients with the acquired immune deficiency syndrome (AIDS) and of 141 T-cell clones established from PB of 3 normal donors were compared for their ability to produce interleukin 2 (IL-2) and gamma-interferon (γ-IFN). Twenty-seven clones from AIDS patients and 85 clones from controls expressed the CD4 phenotype, whereas 49 clones from AIDS patients and 56 clones from controls expressed the CD8 phenotype. There were no significant differences in the proportions of IL-2-producing CD4 T-cell clones established from PB of patients with AIDS and controls, but the mean concentration of IL-2 produced by CD4 clones from AIDS patients was significantly lower than that produced by CD4 clones from controls. Both the proportion of γ-IFN-producing CD4 clones and the mean concentration of γ-IFN produced by CD4 clones were significantly lower in AIDS patients than in controls. In contrast, there were no differences between AIDS patients and normal individuals in the proportion of IL-2- or Y-IFN-producing CD8 clones, or in the mean concentration of IL-2 and v-IFN produced by CD8 clones. These data suggest that the reduced ability of PB T-cells from patients with AIDS to produce IL-2 and v-IFN is not simply due to altered proportions or numbers of T-cell sub-populations, but also reflects intrinsic abnormalities of individual CD4 T lymphocytes.

Effects of subcutaneous interleukin-2 therapy on phenotype and function of peripheral blood mononuclear cells in human immunodeficiency virus infected patients

In the context of clinical therapy with recombinant human interleukin-2 (IL-2), we monitored immunological alteration in 10 human immunodeficiency virus type-I (HIV-1)-infected individuals, on stable antiretroviral therapy, who had a CD4+ cell count between 200 and 500 cells/mm3. Subcutaneous IL-2 was prescribed thrice weekly (at a dose of 3 x 10(6) IU) for 24 weeks and the patients were followed-up for 32 weeks. IL-2 treatment induced an increase in the CD4+ percentage (P<0.001) and CD4+ cell count (P<0.009). Furthermore. natural killer (NK) cell activity was increased (P<0.001) at week 8 of treatment, whereas lymphokine-activated killer (LAK) cell activity showed a transient, nonsignificant increase at week 8 and was reduced (P<0.001) at 32 weeks. However, the cytotoxic T-lymphocyte (CTL) activity decreased against HIV antigens, and the proliferative response to Candida, IL-2 and phytohaemagglutinin (PHA) declined during the first 8 weeks (P<0.05) and returned to baseline levels after 32 weeks. The HIV RNA level did not change during IL-2 therapy; however, after 8 weeks of follow-up a significant increase (P<0.001) in viral load was observed. In

Improvement of lymphocyte proliferation in human immunodeficiency virus infection after recombinant interleukin-2 treatment

In this study, the effect of recombinant interleukin-2 (rIL-2) on the function of peripheral blood mononuclear cells (PBMC) from human immunodeficiency virus (HIV)-infected patients was examined. Using polymerase chain reaction (PCR), an impaired ability of PBMC from 8 patients to respond upon mitogen stimulation with expression of IL-2 and IL-2 receptor (IL-2R) messenger ribonucleic acid (mRNA) was found compared with healthy donors (p = 0.02 and p = 0.05, respectively). Flow cytometry was used to determine the expression of p55 interleukin-2 alpha-receptor (CD25) after phytohaemagglutinin (PHA)-stimulation. Induced CD25 expression in response to stimulation was lower in patient cells than in donor cells (in CD4+ (p = 0.01) and in CD8+ (p = 0.03)). After rlL-2 treatment, the functionality of ex vivo expanded PBMC from patients was restored to the level found in donors. Finally, the induced gene expressions for IL-2 and IL-2R were positively correlated (p < 0.0001), suggesting that the activation of the IL-2 and IL-2R genes in humans may share a common activation pathway, as has been found in monkeys infected by simian immunodeficiency virus (SIV). These results indicate the existence of a reversible IL-2 and IL-2R defect at the pretranscriptional or transcriptional level in PBMC from patients. This may help explain the T-cell anergy found during HIV-infection.

Intralymphatic interleukin-2 in combination with zidovudine for the therapy of patients with AIDS

In a pilot study the safety and therapeutic effects of an immunostimulatory intralymphatic treatment with natural human interleukin-2 (IL-2) in combination with zidovudine were evaluated in nine patients with AIDS. Therapy with IL-2 consisted of one subcutaneous injection of 0.1 microgram/kg IL-2, followed by four intralymphatic IL-2 infusions of 0.1 microgram/kg each within a period of up to 15 days. Enlargement of lymph nodes was seen in six and a transient increase of CD4 cells in five out of nine persons in association with the IL-2 therapy. An increase of HIV p24-antigenemia was observed only in the two patients in whom zidovudine dosage had to be reduced because of side effects. Moderate clinical side effects occurred in eight of the nine patients. Four patients developed zidovudine associated anemia. Six participants showed a favourable course of disease with survival of 25 to 54 months (median 30 months) despite a previous diagnosis of manifest AIDS before IL-2 therapy. This pilot study demonstrates that a combination therapy with intralymphatic IL-2 and zidovudine can induce positive immunomodulatory effects, even in the presence of manifest AIDS. Further studies should explore the tolerability and effects of a prolonged therapy with IL-2 in combination with a more potent antiviral drug combination therapy.

A whole-blood assay for qualitative and semiquantitative measurements of CD69 surface expression on CD4 and CD8 T lymphocytes using flow cytometry

A whole-blood flow cytometry-based assay was utilized to assess CD4 and CD8 T-lymphocyte activation in response to phytohemagglutinin (PHA) stimulation. T-lymphocyte activation was assessed by qualitative (percent CD69) and semiquantitative (anti-CD69 antibody binding capacity) measurements of CD69 surface expression. Whole-blood samples from 21 healthy and 21 human immunodeficiency virus (HIV)-infected (<500 absolute CD4 counts per mm3) individuals were stimulated with 20 microg of PHA per ml for 18 to 24 h. The proportions of activated CD4 and CD8 T lymphocytes expressing CD69 (percent CD69) and the levels of CD69 expression on each T-lymphocyte subset (anti-CD69 antibody binding capacity) were measured. By using this assay system, T-lymphocyte activation was impaired in both CD4 and CD8 T-lymphocyte subsets of HIV-infected individuals. The proportions of CD69-positive CD4 and CD8 T lymphocytes were 43 and 27% lower, respectively, in samples from HIV-infected individuals compared to samples from healthy individuals. Similarly, the levels of CD69 expression on each activated CD4 and CD8 T-lymphocyte subset were 48 and 51% lower, respectively. These results suggest that both qualitative and semiquantitative measurements of CD69 surface expression by flow cytometry can be used to assess T-lymphocyte activation.

CD69 expression reliably predicts the anti-CD3-induced proliferative response of lymphocytes from human immunodeficiency virus type 1-infected patients

Published studies suggest that mitogenic responses of lymphocytes can be reliably assessed by monitoring the expression of lymphocyte surface CD69 after 24 h of culture with the stimulant. We tested this hypothesis by determining the ability of lymphocyte CD69 expression to predict the outcome (normal or abnormal) of lymphocyte proliferative responses to anti-CD3 in a group of human immunodeficiency virus type 1 (HIV-1)-infected patients (n = 47). Cutoff values for defining normal and abnormal CD69 expression and proliferative ([3H]thymidine incorporation) responses were established with lymphocytes from healthy uninfected controls (n = 20). Lymphocytes from 29 HIV-infected patients exhibited an abnormal proliferative response, and those from 25 of the 29 also exhibited abnormal CD69 expression (sensitivity, 86.2%). Similarly, lymphocytes from 18 HIV-infected patients exhibited a normal proliferative response, and those from 16 of the 18 also exhibited normal CD69 expression (specificity, 88.9%). The predictive value of a normal CD69 result was 80%, and the predictive value of an abnormal CD69 result was 92.6%. These findings demonstrate that HIV-1-associated impairments in lymphocyte activation can be reliably detected by the rapid and nonradioactive CD69 expression assay.

Calmodulin-binding function of LLP segments from the HIV type 1 transmembrane protein is conserved among natural sequence variants

LLP1 is a peptide, derived from the cytoplasmic tail of HIV-1 TM glycoprotein, that binds and inhibits calmodulin; this region is generally conserved among isolates, but amino acid variation does exist both within clade B and among different clades, as well as SIV. In light of previous studies showing that selected single amino acid changes can have a qualitatively significant effect on the calmodulin-binding properties of this peptide, we sought to examine the properties of naturally occurring variant LLP1 sequences. Using a quantitative fluorescence-based method to measure dissociation constants of calmodulin-LLP1 complexes, a remarkable conservation of calmodulin-binding function among natural variants was revealed. In contrast, engineered nonconservative single amino acid changes altered the affinity of the peptide for calmodulin. The results show that the calmodulin-binding function is well preserved despite the sequence variation observed in nature, suggesting that this region of the TM protein is important to viral replication.

The serotonin analogue buspirone increases the function of PBMC from HIV-infected individuals in vitro

HIV infection is characterized by the loss of CD4+ T cell numbers as well as loss of T cell function leading to severe immunodeficiency. The proliferative capacity of T cells, measured in vitro as response to antigens and mitogens, is severely reduced during HIV infection. An increased level of the intracellular second messenger cAMP has been demonstrated to cause impaired proliferative capacity of PBMC from HIV-infected individuals in vitro. We have identified a serotonin analogue, buspirone, that inhibits the activity of adenylyl cyclase, the enzyme responsible for regulation of intracellular levels of cAMP. Using this inhibitor the proliferative responses of PBMC to a polyclone activator in vitro were increased in 28/30 HIV-seropositive individuals (p < 0.00001). Further, we demonstrated that this was due to proliferation of CD4+ T cells and that buspirone induced expression of IL-2 mRNA.

Interleukin-2 and human immunodeficiency virus infection: pathogenic mechanisms and potential for immunologic enhancement

A hallmark of human immunodeficiency virus (HIV) infection is the progressive loss of CD4+ T lymphocytes; however, qualitative defects in immune responses occur prior to the precipitous drop CD4+ T cell numbers. One of the first immunologic defects to be described in HIV-infected individuals is a deficiency in interleukin (IL)-2 production. The addition of IL-2 in vitro to cultures of mononuclear cells from HIV-infected individuals partially or completely restored certain defective cellular immune responses. However, production of or addition of IL-2 has also been associated with increased viral replication in infected T cells. These observations underscore the pernicious correlation between immune activation and HIV replication. However, recent in vitro and in vivo studies have provided promising preliminary results suggesting that, at least at certain stages of disease, the benefits of IL-2 mediated immune enhancement may outweigh or override the inductive effects of this cytokine on HIV production.

Cytokine interactions in human immunodeficiency virus-infected individuals: roles of interleukin (IL)-2, IL-12, and IL-15

Cytokines have been shown to be powerful regulators of the immune response. In this study, we analyze the effect that the newly recognized cytokine interleukin (IL)-15 has on proliferation and cytokine induction using peripheral blood mononuclear cells (PBMCs) and purified CD4+ T cells from patients infected with human immunodeficiency virus (HIV) who are at various stages in their disease. We observed that IL-15 enhances the proliferative response in a dose-dependent manner from PBMCs of HIV-infected individuals when stimulated by polyclonal mitogen, tetanus toxoid, or HIV-specific antigen. The effects of exogenous IL-15 are substantially diminished by adding a neutralizing antibody to the beta chain of the IL-2 receptor. Moreover, the ability of IL-15 to increase proliferation is enhanced by the presence of endogenous IL-2 produced in the cultures. The effect that exogenous IL-15 had on IL-2, IL-4, and interferon (IFN)-gamma induction from PBMC's or CD4+ T cells in response to mitogen or tetanus toxoid was also examined. This was compared to the effect that exogenous IL-2 and IL-12 had under the same conditions. Addition of IL-2 or IL-15 to short-term in vitro cultures of either PBMCs or CD4+ T cells had little effect on IL-2, IL-4, or IFN-gamma production. By contrast, IL-12 caused substantial enhancement of both IL-2 and IFN-gamma production from these cultures. The role that endogenous cytokines have on IFN-gamma induction was also studied. Addition of a neutralizing antibody to the alpha chain of the IL-2 receptor or IL-12 to antigen stimulated cultures caused a striking decrease in IFN-gamma production. Neutralization of endogenous IL-15 also resulted in diminished IFN-gamma production from cultures stimulated with mitogen. IL-4 and IFN-gamma protein production by PBMCs and CD4+ T cells stimulated with mitogen was assessed to see if we could detect a specific bias of cytokine production. Small amounts of IL-4 were detected from CD4+ T cells but not PBMCs from most individuals tested. IFN-gamma and IL-2, however, were also produced from these same cultures. These results further elucidate the mechanism of cytokine regulation in HIV-infected individuals, and they provide evidence that IL-15 may be a useful immune modulator.

Bioactivity of recombinant feline interleukin-2 on human and feline leukocytes

Interleukin (IL)-2 is a 16,000 Da protein product of T lymphocytes which is the principle cytokine responsible for clonal expansion of T lymphocytes as a response to antigen exposure. Deficiency of functional IL-2 plays a pivotal role in the pathogenesis of human immunodeficiency syndrome and may be important in the pathogenesis of feline immunodeficiency syndrome as well. Additionally, IL-2 may enhance secretion of interleukin-5 from the TH2 subset of CD4+ T cells, promote peripheral and systemic eosinophilia, and contribute to the eosinophilia which characterizes the inflamed airways of human beings and cats with asthma. We recently reported the sequence of feline IL-2 and the synthesis of recombinant feline IL-2. The purpose of the present study was to evaluate the bioactivity of recombinant feline IL-2 on human and feline leukocytes. We established dose-response relationships between recombinant feline IL-2 and radiolabeled proliferating human and feline leukocytes using thymidine incorporation as a marker of bioactivity. We found that recombinant human IL-2 promotes proliferation of both human and feline leukocytes. However, recombinant feline IL-2 promotes proliferation of feline cells, but not human cells.

Effect of amino acid substitutions on calmodulin binding and cytolytic properties of the LLP-1 peptide segment of human immunodeficiency virus type 1 transmembrane protein

Previous studies have identified two highly basic amphipathic helical regions in the human immunodeficiency virus type 1 transmembrane protein that, in vitro, display both cytolytic and calmodulin-binding and -inhibitory properties that could contribute to cellular dysfunctions and cytopathogenesis during a persistent viral infection. In the current study, the structural specificity of the cytolytic and calmodulin-binding activities of the human immunodeficiency virus type 1 lentivirus lytic peptide (LLP-1) are examined with synthetic peptide homologs and analogs. The results of these studies demonstrate that even minor changes in LLP-1 amino acid content can markedly affect these properties, suggesting that sequence variation in these highly conserved LLP sequences may correlate with alterations in viral cytopathic properties.

Identification of a calmodulin-binding and inhibitory peptide domain in the HIV-1 transmembrane glycoprotein

A number of studies suggest a critical role of the HIV-1 envelope glycoprotein in cytopathogenesis, but the detailed mechanisms of cell injury remain to be defined. HIV-1 envelope proteins associate with the host cell membrane, and studies have demonstrated that HIV perturbs membrane structure and function. We describe here a structurally conserved region of the HIV-1 transmembrane protein (TM) that displays functional properties of target regions of proteins that interact directly with calcium-saturated calmodulin as part of cellular response cascades. The synthetic peptide homolog encompassing the carboxyl terminus (amino acid residues 828-855) of HIV-1 TM protein (LLP-1) is shown in standard in vitro assays to bind efficiently to purified calmodulin (CaM) and to inhibit in vitro CaM-mediated stimulation of phosphodiesterase activity. This suggests that this peptide homolog binds to CaM at affinities similar to those reported for a reference CaM-binding peptide. In addition, the CaM-dependent process of phospholipid synthesis can be inhibited in cell cultures by exogenous addition of the LLP-1. Finally, we have shown that the full-length TM protein binds CaM, whereas a truncated TM protein lacking the LLP-1 segment does not bind CaM. These results suggest a novel mechanism of viral cytopathogenesis mediated by the interaction of HIV-1 TM protein with cellular CaM, that could lead to an uncoupling of critical cellular signal transduction pathways.

Prolonged immunostimulatory effect of low-dose polyethylene glycol interleukin 2 in patients with human immunodeficiency virus type 1 infection

13 patients with human immunodeficiency virus type 1 infection class II-IV, but without opportunistic infection or neoplasm, received 6 micrograms (3.6 x 10(4) IU) of polyethylene glycol recombinant human interleukin 2 (PEG IL-2) intradermally twice a week for 4 mo were then followed for an additional 6 mo. Clinical, immunological, and viral parameters were monitored in the patients, all of whom were taking zidovudine. The cutaneous administration of PEG IL-2 resulted in an indurated zone resembling a delayed-type hypersensitivity response of 26 +/- 1 mm diameter (676 mm2) at 72-96 h after injection throughout the 4 mo of administration. This dose, which was appreciably lower than in most previous trials, was not associated with local or systemic toxicity. No increase in the viral burden of circulating leukocytes or plasma occurred. A number of immunological functions were stimulated by this course of therapy. All patients demonstrated high levels of lymphokine-activated killer cell activity by cells freshly removed from the circulation and in the absence of in vitro exposure to IL-2. Natural killer cell activity was also enhanced. Limiting dilution analysis revealed an increase in the frequency of IL-2-responsive cells from abnormally low to levels above normal during the course of injections. In a subgroup of four patients with > or = 400 CD4+ T cells/microliter at entry, there was a trend to sustained increases in CD4+ T cell numbers. However, this increase did not reach statistical significance. This subset of patients also exhibited higher proliferative responses to phytohemagglutinin as mitogen. Several of these effects persisted for 3-6 mo after cessation of therapy. In conclusion, low-dose IL-2 regimens lead to sustained immune enhancement in the absence of toxicity. We suggest pursuit of this approach for further clinical trials both as prophylaxis and therapy.

Relationship between IL-2 receptor expression and proliferative responses in lymphocytes from HIV-1 seropositive homosexual men

Previous studies have shown that exogenous IL-2 does not correct the reduction in phytohaemagglutinin (PHA)-induced proliferation of lymphocytes from HIV-1 infected (HIV+) individuals. We investigated the mechanism of this reduction to determine if reduced expression of the complete IL-2 receptor (IL-2R) was responsible. In a series of experiments, PHA-stimulated lymphocytes from a total of 89 HIV- and 93 HIV+ homosexual men from the Baltimore Multicentre AIDS Cohort Study (MACS) were studied to determine the expression of messages for the alpha and beta subunits of the IL-2R, the binding of 125I-IL-2 to high affinity IL-2R, and the effect of IL-2 on cell proliferation. Compared to HIV- donors, PHA-stimulated lymphocytes from most HIV+ donors demonstrated (i) a reduction in high affinity IL-2R expression that correlated with the reduction in the IL-2-induced proliferative response; and (ii) a reduction in expression of both IL-2R alpha- and beta-chain mRNA which may be responsible for decreased high affinity IL-2R expression. However, lymphocytes from some HIV+ individuals had borderline low IL-2-induced proliferation despite normal or elevated expression of high affinity IL-2R. These results suggest that decreased expression of IL-2R may account, at least in part, for the lower proliferative response of cells from HIV+ donors.

Human immunodeficiency virus-infected adherent cell-derived inhibitory factor (p29) inhibits normal T cell proliferation through decreased expression of high affinity interleukin-2 receptors and production of interleukin-2

Adherent cells from HIV-infected subjects as well as in vitro HIV-infected normal adherent cells produce spontaneously a 29-kD (p29) factor that inhibits mitogen-induced proliferation of normal T cells. p29 mediates a partial dose-dependent inhibition of total protein synthesis in both nonstimulated and PHA-activated cells that is associated with impaired PHA-induced expression of IL-2 receptor (IL-2R)alpha chain, HLA-class II molecules, and production of IL-2 by these cells; conversely, p29 does not modify the expression of IL-2R beta chain, 4F2, CD9, or transferrin receptor, or the production of IL-1 and TNF alpha by the cells. 1 h preincubation of the cells with p29 is sufficient to detect its biologic activity and added rIL-2 abrogates p29-induced inhibition of IL-2R alpha chain expression; however, p29 does not display any biologic effect on already expressed IL-2R alpha chains. The impaired expression of IL-2R alpha chain mediated by p29 is not due to a decreased accumulation of the corresponding mRNA transcripts, but is associated with a two-fold increase of intracellular cAMP. Binding experiments with 125I-rIL-2 reveals that p29 induces a 50% decrease in the number of both high and low affinity IL-2R per cell. p29 also inhibits alloantigen-induced proliferation of PBMC, whereas it does not modify IL-2-dependent proliferation of 48-h PHA-blasts that already express high affinity IL-2R. These findings indicate that p29 mediates its biologic activity during early stages of T cell activation affecting the expression of high affinity IL-2R and production of IL-2, through a nontranscriptional mechanism involving an increase of intracellular cAMP.

Abnormal expression of IL-2R beta (p70)-binding polypeptide on HIV-infected patients' cells

The constitutively expressed IL-2R beta (p70) chain participates in the formation of high-affinity (h.a.) IL-2R and transduces IL-2-mediated signals to normal cells. Its expression on HIV-infected patients' PBMC was evaluated and was found to be decreased in both nonstimulated CD4+ and CD8+ cells. Mitogenic cell stimulation induced IL-2R beta chain expression on both CD4+ and CD8+ cells from asymptomatic and persistent generalized lymphadenopathy patients but not on those from AIDS patients. Comparison of mean fluorescence intensity of IL-2R beta positively stained cells from normals and patients did not reveal significant differences. Cross-linking of 125I-rIL-2 on patients' PHA-blasts revealed decreased signals corresponding to both IL-2-binding chains and, in some cases, neither IL-2R alpha nor IL-2R beta chains could be detected. Decreased expression of IL-2R beta polypeptide was associated with impaired accumulation of the corresponding mRNA transcripts. Binding experiments with 125I-rIL-2 under h.a. conditions showed a decreased number of IL-2-binding sites/cell which was more pronounced in patients with AIDS than in patients with less advanced clinical stages. In vitro HIV infection of normal PHA-blasts also resulted in a decreased number of h.a. IL-2R/cell. High concentrations of rIL-2 in the absence of other mitogenic stimuli induced a decreased cell proliferation and expression of the IL-2R alpha chain and did not enhance the constitutive NK and the generation of LAK activity in several patients, suggesting an impaired IL-2R beta chain-mediated cell activation.

A comparative study of natural killer cell activity, lymphoproliferation, and cell phenotypes in nonhuman primates

Three different species of nonhuman primates (baboons [Papio hamadryas], rhesus monkeys [Macaca mulatta], and African green monkeys [Cercopithecus aethiops]) were evaluated for their natural killer cell activity, and for the ability of their peripheral blood mononuclear cells to proliferate in response to known mitogens (concanavalin A, phytohemagglutinin, and pokeweed mitogen) and to react with a panel of mouse monoclonal antibodies directed against human leukocyte surface antigens. Rhesus monkeys displayed the highest natural killer cell cytotoxic activity (185.7 +/- 33 lytic units) compared with those of baboons (83.8 +/- 19 lytic units) and of African green monkeys from West Africa (39.08 +/- 8 lytic units) and from the Caribbean basin (37.9 +/- 9 lytic units). No correlation was observed between the natural killer cell cytotoxic activity and the percentage of CD16+ natural killer cells among the three species studied. High spontaneous proliferative capacity was observed in African green monkeys obtained from West Africa compared with those of the other species studied. Although no significant differences were noted in T and B cell mitogen-induced in vitro proliferation, baboon mononuclear cells were less responsive to concanavalin A (stimulation index of 16 +/- 3 [mean +/- standard error of mean]) than to phytohemagglutinin (stimulation index of 47 +/- 12). However, rhesus and African green monkey cells proliferated more efficiently in response to concanavalin A. Unlike in human beings where the ratio between helper-inducer (CD4+) and cytotoxic-suppressor (CD8+) T-lymphocytes is generally greater than 1, the CD4+/CD8+ ratios in baboons and rhesus and African green monkeys were 0.58, 0.69, and 0.35, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Lymphoproliferative responses to mitogen and antigen in HIV-infected children

We endeavored to study lymphoproliferative responses in children with human immunodeficiency virus (HIV) infection and to compare them with normal control children. Children were grouped according to age; 6-18 months and greater than 18 months, and according to CDC classification: asymptomatic (P1), mildly symptomatic (P2A), and advanced symptoms (P2D). Absolute CD4 and CD8 numbers were compared and found to be higher in the younger age groups. The children in P1 and P2A classes demonstrated an increase in CD8+ cells; only the children with AIDS showed a significant decrease in CD4+ cells. Lymphoproliferative responses to phytohemagglutinin A (PHA) were compared to tetanus toxoid. Only the children with acquired immunodeficiency syndrome (AIDS) (P2D) in the older group and only the symptomatic children (P2A and P2D) in the younger group showed a significant decrease in proliferative responses to PHA. All classes of infected children demonstrated a significant decrease in response to tetanus toxoid. We have been able to demonstrate a loss of antigen responsiveness which precedes the loss of mitogenic responsiveness. Furthermore, we have been able to demonstrate an age related increase in lymphoproliferative responses to both PHA and tetanus in HIV-infected and control children. Therefore, we conclude that children are particularly susceptible to the immunologic effects of HIV infection. Loss of lymphoproliferative responses to antigen occurs early in infected children and precedes the loss of CD4+ helper cells and of PHA responsiveness. This increased susceptibility to the immunopathogenesis of HIV infection is due, at least in part, to the relative immunodeficiency of infancy.

Effect of HIV on antigen presentation by dendritic cells and macrophages

The antigen-presenting function of dendritic cells (DC) and macrophages (MO) following infection with HIV in vitro was examined. Using non-infected cells, DC, but not MO, stimulated primary proliferative responses in allogeneic lymphocytes in the mixed leukocyte reaction. Both DC and MO stimulated secondary responses to influenza virus and to tetanus toxoid in autologous T lymphocytes. After exposure of DC and MO to HIV1 in vitro for 2 days, 27% of DC but less than 1% MO became infected as assessed by in situ hybridization. DC were blocked in their capacity to stimulate responses to alloantigens or to the recall antigens. By contrast, MO retained the ability to stimulate responses to the recall antigens. Similar effects during in vivo infection would allow activated T-cell clones to respond to antigens presented by MO early in infection. However, any loss of activated T cells might prove cumulative and damaging in the absence of an effective DC recruitment mechanism for resting T cells.

Human immunodeficiency virus infection: association with altered intracellular levels of cAMP and cGMP in MT-4 cells

T-cells from human immunodeficiency virus (HIV)-infected patients are characterized by a number of qualitative deficiencies including defective T-cell activation. The latter has previously been shown to be normally regulated by cAMP. In this study the patterns of cAMP and cGMP induction in MT-4 cells following HIV infection were investigated. The MT-4 cells were infected with HIV (strain IIIb) and at selected times postinfection (p.i.), culture supernatants were tested for HIV replication by reverse transcriptase activity or HIV P24 Ag. The cells were also examined for their intracellular levels of cAMP and cGMP by radioimmunoassay. HIV infection was associated with an increase in intracellular levels of cAMP and cGMP. The cAMP was increased 40-fold by Day 8 and cGMP 4-fold by Day 4 Pl. The increase in intracellular levels of the cyclic nucleotides (CN) were virus specific, dependent on virus dosage, genetically conserved among the two fresh patient isolates tested, and were abolished by uv inactivation. An increase in cAMP and cGMP was also observed in other cell lines infected with HIV. The sustained elevation in CN level observed could certainly influence cell activation and HIV replication and may potentially have clinical relevance.

Host defense abnormalities associated with HIV infection

Infection with human immunodeficiency virus (HIV) impairs immune function. Most abnormalities in host defense associated with HIV infection are due to helper T-cell dysfunction. Studies defining these abnormalities in the HIV-infected patient have largely been done in adults. A more complete understanding of the immunodeficiency that occurs in infants and young children congenitally infected with HIV awaits further study of their immune function and the effect this virus has on the developing immune system.

Sarcoidosis: in search of Kveim reactivity in vitro

Granuloma formation in patients with sarcoidosis may be evoked by the intradermal injection of homogenised sarcoid tissue (the Kveim reaction). Attempts to demonstrate an in vitro counterpart of the reaction have been unsuccessful. The cytokine interleukin-2 (IL-2) enhances immune responses in vivo and in vitro. We report here an attempt to amplify the Kveim reaction by the addition of IL-2. We studied the effect of Kveim reagent on the proliferative responses of peripheral blood mononuclear cells (PBMC) in the presence or absence of exogenous IL-2. Twenty-eight patients were studied and 14 healthy subjects served as controls. PBMC were cultured, in vitro, in the presence of Kveim reagent. Recombinant IL-2 or both of these combined. Proliferative responses were measured by [3H]-thymidine incorporation. The response of patients' PBMC in the presence of Kveim reagent at a dilution of 1:40 was significantly below the unstimulated response (P less than 0.01). Kveim reagent at a dilution of 1:40 also inhibited the proliferative response of patients PBMC to IL-2 (P less than 0.005); greater dilutions (1:100 and 1:1000) of Kveim reagent were not inhibitory. Responses of PBMC from control subjects (both unstimulated and IL-2 generated) were reduced in the presence of Kveim reagent, however, these reductions were not statistically significant.

Synthetic peptides corresponding to sequences in HIV envelope gp41 and gp120 enhance in vitro production of interleukin-1 and tumor necrosis factor but depress production of interferon-alpha, interferon-gamma and interleukin-2

Patients with human immunodeficiency virus (HIV) infections have aberrant production of a number of lymphokines and monokines. Envelope glycoproteins are believed to be important in HIV pathogenesis and may influence the production of these cytokines. Therefore, synthetic peptides corresponding to amino acid sequences 735-752 and 846-860 of glycoprotein gp41 and to amino acid sequence 304-328 of gp120 were investigated for their abilities to affect the production of the following cytokines by normal peripheral blood mononuclear cells in the presence of appropriate inducers: interferon (IFN)-alpha, IFN-gamma, interleukin (IL)-1, IL-2, and tumor necrosis factor (TNF). In contrast to cells and inducers alone (or in the presence of a control peptide), gp41 or gp120 synthetic peptides were able to depress the production of IFN-alpha, IFN-gamma and IL-2. In contrast, these peptides produced an elevation of the production of IL-1 and TNF. The effect of the gp41 peptides was more marked than that of gp120 peptides in most cases. These studies indicate that these HIV envelope glycoproteins may be directly responsible for aberrant lymphokine and monokine production in patients infected with this virus and therefore may be at least partially responsible for the pathogenesis of AIDS.

Production of interleukins in human immunodeficiency virus-1-replicating lymph nodes

To document the in vivo interactions occurring between the immune system and HIV replicating cells, we analyzed using in situ hybridization the production of IL-1 beta, IL-6, IL-2, and INF-gamma in eight hyperplastic lymph nodes from HIV-1 infected patients. Numerous IL-1 beta- and IL-6-producing cells associated in clusters were detected in sinuses. Few individual IL-1 beta- and IL-6-producing cells were present in interfollicular and follicular areas. IL-2- and INF-gamma-producing cells were observed in all lymph node compartments, with a selective enrichment in germinal centers. The amount and distribution of IL-1 beta, IL-6-, and IL-2-producing cells in HIV lymph nodes were not different from those found in six HIV unrelated hyperplastic lymph nodes. In contrast, a higher level of INF-gamma production was observed in HIV-1 lymph nodes. The CD8+ cells that accumulate in germinal centers of HIV lymph nodes (and not in non-HIV germinal centers) were actively involved in this INF-gamma production. INF-gamma synthesizing cells were in direct contact with cells containing HIV core antigens and HIV RNA. Thus a high INF-gamma production may characterize anti-HIV T cell immune response, potentially contributing to control of viral spreading as well as to the development of follicle lysis.

Combined immunodeficiency due to the selective absence of CD4 inducer T lymphocytes

Selective congenital deficiency of the CD4 inducer T lymphocyte subset is a recently described variant of combined immunodeficiency. To further characterize the cellular and molecular mechanisms which lead to the profound T and B cell immunodeficiency in this condition, we examined in vitro immunoregulatory T lymphocyte activation and effector function, interleukin-2 (IL-2) synthesis, IL-2 receptor generation, and CD4 gene structure. Immunophenotyping of T lymphocytes demonstrated a selective deficiency of CD4+ cells, with normal numbers of CD2+ and CD3+ T cells, nearly all of which expressed the CD8+ determinant. Mitogen- and alloantigen-induced blastogenesis was profoundly decreased. B lymphocytes were present in normal numbers but there was a functional dysgammaglobulinemia (low IgG, normal IgM, low IgA) with no antibody response to in vivo immunization. T cells from the patient did not provide help to normal B cells for in vitro immunoglobulin synthesis; however, the patient's B cells were capable of synthesizing normal amounts of IgG when provided help from normal T cells. Concanavalin A failed to activate suppressor-inducer function in the patient's T cells. However, CD8+ T cell-mediated suppression was expressed if the patients T cells were cocultured with normal CD4+ T cells in a pokeweed mitogen-stimulated IgG secretion assay. IL-2 secretion and IL-2 receptor expression were both markedly reduced. Southern blot analysis of genomic DNA revealed no obvious abnormality in CD4 gene structure. The global defects in T cell activation, effector function, immunoregulation, and lymphokine generation observed in CD4+ inducer lymphocyte deficiency emphasizes the central role that the CD4 T lymphocyte plays in the activation and regulation in vivo immune responses.

In vitro interactions of cytokines and bovine viral diarrhea virus in phytohemagglutinin-stimulated bovine mononuclear cells

Bovine viral diarrhea (BVD) virus inhibited phytohemagglutinin (PHA)-stimulated bovine peripheral blood mononuclear cell (PBMC) proliferation and bovine interleukin-2 (IL-2) production. In the controls, the heat-inactivated BVD virus was not capable of suppressing the PHA-stimulated PBMC proliferation. Presence of exogenous cytokines, such as purified human IL-2, recombinant bovine interleukin-1 (rbovIL-1), recombinant bovine IL-2, and recombinant human IL-6 failed to reverse the BVD virus-induced immunosuppression. Also, we found that the BVD virus inhibited PHA and IL-2 induced proliferation of bovine PBMC in the early and late stages of activation. In summary, our data suggest that BVD virus induced immunosuppression was not due to destruction of the PBMC but may be inhibiting one or more of the important intracellular enzymes that may regulate PBMC proliferation.

Patterns of interferon-gamma production by peripheral blood mononuclear cells from patients with human immunodeficiency virus infection

A number of immune parameters have been described as impaired in AIDS patients. The patterns of interferon-gamma (IFN-gamma) production by peripheral blood mononuclear cells (PBMC) from AIDS-related complex (ARC) and AIDS patients in response to specific and nonspecific mitogens and their relationship to proliferative responses, interaction with exogenous interleukin 2 (IL-2), and absolute CD4 cell counts were studied. The PBMC were exposed to phytohemagglutinin (PHA) or cytomegalovirus (CMV) antigen (Ag) and/or 10 units of IL-2. At selected times, culture supernatants were tested for IFN-gamma production by radioimmunoassay and at identical times proliferative responses were determined by [3H]thymidine uptake. IFN-gamma production in response to PHA or CMV Ag was inhibited significantly and appeared dependent on absolute CD4 cell counts. Proliferative responses were also similarly decreased. While IFN-gamma production to PHA was severely inhibited in PBMC only from patients with less than 100 CD4 cells/mm3, equivalent inhibition in response to CMV Ag was observed only in those with CD4 counts less than 600/mm3. IL-2 enhanced the PHA and CMV Ag-induced IFN production significantly by 2.8- and 5.3-fold respectively. Therefore, the administration of IL-2 might improve certain cell-mediated immune responses.

Serum factors in the progression of human immunodeficiency virus type 1 infection to AIDS

We studied the prevalence of four serum factors in individuals at different stages of human immunodeficiency virus-1 (HIV-1) infection. Soluble interleukin-2 receptors (sIL-2R) were elevated in all antibody-positive groups compared with high-risk, antibody-negative controls. Paraproteins, usually of the IgG-kappa isotype, were found in the sera of a significant number of HIV-1-infected individuals as were antibodies to lymphocytes (ALAs). Serum factors that inhibit proliferation of peripheral blood mononuclear cells from healthy donors appear late in the course of infection and were associated with increasing clinical severity. Measurement of these factors may prove to be useful in defining the stages of infection and in predicting the appearance or exacerbation of symptoms. They may also play a role in the development of the HIV-1-induced immune defects that lead to the expression of clinical acquired immunodeficiency syndrome.

Lymphocyte phenotype does not predict immune function in pediatric patients infected with human immunodeficiency virus type 1

To determine whether assays of lymphocyte phenotype were predictive of antigen-specific immunologic function in children infected with human immunodeficiency virus type 1 (HIV-1), we compared the antigen-specific cellular and humoral functions (tetanus toxoid-induced T lymphocyte blastogenesis and anti-tetanus toxoid antibody) with the patients' T lymphocyte phenotype, determined at the same time. Although both HIV-1-infected patient populations studied (pediatric hemophilia patients and other pediatric patients) had decreases in the values determined by their functional and phenotypic assays, no association between the functional and phenotypic assays was demonstrated. Thus some HIV-1-infected patients with a normal phenotype had no antigen-specific function, whereas other patients with a markedly abnormal T lymphocyte phenotype had normal antigen specific T lymphocyte function. These results indicate that the assessment of HIV-1-infected patients should include assays of antigen-specific immune function in addition to assays of T lymphocyte phenotype.

Recombinant human gamma interferon enhances in vitro activation of lymphocytes isolated from patients with acquired immunodeficiency syndrome

Decreased responses to antigens and lectins are a characteristic feature of peripheral blood lymphocytes isolated from patients with the acquired immunodeficiency syndrome (AIDS). The in vitro addition of recombinant gamma interferon (IFN-gamma) to cultures of peripheral blood lymphocytes obtained from patients with AIDS resulted in an augmented proliferative response [( 3H]thymidine uptake) to phytohemagglutinin (PHA) and an enrichment in CD4+ and CD8+ T lymphocytes. In AIDS cultures stimulated with PHA, IFN-gamma increased the release of T-cell growth factors and enhanced the expression of interleukin-2 receptors on activated lymphocytes. Responsiveness to PHA was augmented, albeit to a lesser extent, by IFN-gamma in cultures derived from normal donors. Proliferation to microbial antigens including herpes simplex virus, cytomegalo virus, and Candida albicans was increased by IFN-gamma in cultures established from a group of AIDS patients with Kaposi's sarcoma who had no history of opportunistic infection.

The potential role of serum ferritin in the pathogenesis of acquired immune deficiency syndrome (AIDS)

Elevated serum ferritin levels have been observed in several disease states including various malignancies, inflammatory states, and the acquired immunodeficiency syndrome (AIDS). This discussion will examine the normal sequence of events in T cell activation and proliferation, as well as the various defects in these events, and monocyte/macrophage and NK cell activity seen in AIDS patients. Further, the potential role of a serum suppressor factor as a contributor to the profound immunosuppression seen in AIDS will be discussed, as will evidence suggesting that ferritin may be this factor. A model is presented to explain mechanisms by which ferritin might suppress immune function and further studies to elaborate these mechanisms are proposed.

Differential reconstitution of zidovudine-induced inhibition of mitogenic responses by interleukin-2 in peripheral blood mononuclear cells from patients with human immunodeficiency virus infection

Zidovudine (ZDV), an anti-human immunodeficiency virus (HIV) therapy, has been associated with reduction in mortality and improvement of patients with acquired immunodeficiency syndrome (AIDS). The ZDV recipients, however, experience a multitude of side effects of which bone marrow suppression is the most noteworthy, especially among patients with low CD4 cell counts. The effect of ZDV and interleukin-2 (IL-2) on phytohemagglutinin (PHA)-induced proliferative response of peripheral blood mononuclear cells (PBMs) from patients with HIV infection was investigated. ZDV 0.5 micrograms inhibited 40% of PHA-induced thymidine uptake in PBMs from healthy donors or patients with HIV, irrespective of their CD4 cell counts. However, IL-2 (10 U/ml) had differential effect on PHA-induced thymidine uptake that appeared to be dependent on absolute CD4 cell counts. While PBMs from patients with CD4 cell counts of 400/mm3 or more did not respond to IL-2 (low responders), IL-2 enhanced the PHA-induced thymidine uptake in PBMs from patients with CD4 cell counts less than 400/mm3 at an average of 60% (high responders). Moreover, IL-2 restored the ZDV-induced inhibition by almost 100% in the high responder group while it did not affect counts in the low responder group. The production of IL-2 in vitro, in response to PHA or recall antigens, was equivalently inhibited in both groups. These data suggest that ZDV and IL-2 could have an additive effect on immune parameters in certain groups of patients infected with HIV. The differential effect of IL-2 was independent of IL-2 receptor expression.

Impairment in T-lymphocyte responses during early infection with the human immunodeficiency virus

Uncertainty has existed as to whether a T-cell deficiency exists in human immunodeficiency virus (HIV) infection different from that inherent in the reduced T-cell numbers characteristic of the disease. Heretofore, methods for measuring T-cell responses in patients have been carried out with systems requiring monocytes as accessory cells. In the presence of high concentrations of interleukin-2, however, highly purified T cells respond in a monocyte-independent fashion to antibody reactive with the CD3 component of the antigen receptor complex Ti/CD3. Highly purified T cells of HIV-infected patients responded subnormally in this anti-CD3/IL-2 system, even in the case of patients who were asymptomatic or had only lymphadenopathy. The defective T-cell responses occurred over a wide range of concentrations of the anti-CD3. Neither poor IL-2 receptor function as reflected by responses to limiting dilutions of IL-2 nor IL-1 receptor function as defined by incremental proliferation when IL-1 is added accounted for this defect, which also correlated poorly with T4 and T8 numbers. These results suggested that the T-cell abnormality was closely related to Ti/CD3 function, was not specifically or restrictively associated with T4 cells, and was not due to defective IL-2- or IL-1-receptor functions. The amount of HIV RNA in 10(5) T lymphocytes from the patients amounted to less than that found in one cell of a standard HIV infected laboratory cell line (CEM), using slot-blot hybridization. Thus the T-cell deficiency we have observed was not likely to be due directly to cell killing by HIV resident in the T4 cells. Other factors may be important in inducing the immunodeficiency, some of which are discussed.

Defective cell mediated immunity in sarcoidosis: effect of interleukin-2

Interleukin-2 has been reported to enhance the immune response in diseases characterised by defective cell mediated immunity. The effect of exogenous recombinant interleukin-2 was studied on the proliferative and cytotoxic responses of peripheral blood mononuclear cells from 39 patients with sarcoidosis and 14 healthy control subjects. The proliferative response to purified protein derivative was smaller in patients than in control subjects (p less than 0.001) whereas the response to 80 U interleukin-2 alone and to purified protein derivative and interleukin-2 did not differ significantly between the two groups. In addition, in eight patients but no control subjects tritiated thymidine incorporation induced by the combination of purified protein derivative and interleukin-2 was more than twice the sum of that induced by purified protein derivative and interleukin separately. Cytotoxic activity occurring spontaneously and induced by purified protein derivative and interleukin-2 in blood mononuclear cells was significantly less for patients with sarcoidosis than for control subjects (p less than 0.05 spontaneous, less than 0.001 purified protein derivative induced, less than 0.02 interleukin induced). Synergism between antigen and interleukin did not occur with respect to the cytotoxic response in either patients or controls. Defective interleukin-2 production may contribute to, but does not entirely explain, the functional abnormalities of peripheral blood lymphocytes from patients with sarcoidosis.

Downregulation of interferon alpha but not gamma receptor expression in vivo in the acquired immunodeficiency syndrome

Interferons (IFN) elicit antiviral and antineoplastic activities by binding to specific receptors on the cell surface. In evaluating the role of IFN as therapeutic agents in AIDS, we investigated the expression of IFN alpha and gamma receptors on peripheral blood mononuclear cells (PBM) from patients with AIDS, ARC, and heterosexual control subjects using radioiodinated IFN alpha 2 and IFN gamma. The binding characteristics of the 125I-IFN alpha and gamma to PBM were analyzed to determine receptor numbers and dissociation constants. PBM from controls expressed 498 +/- 247 IFN alpha receptor sites/cell (n = 17). However, eight patients with ARC and seven patients with AIDS had a mean number of IFN alpha receptor/cell of 286 +/- 235 (P less than 0.05) and 92 +/- 88 (P less than 0.001), respectively. This was consistent with elevated levels of serum acid-labile IFN alpha and cellular 2-5A synthetase activity in patients. Treatment of PBM from the AIDS patients with exogenous IFN alpha in vitro resulted in minimal 2-5A synthetase induction in comparison to controls. In contrast, the expression of IFN gamma receptors in ARC (n = 5) and AIDS (n = 4) patients remained normal. Thus the decrease in IFN alpha receptor expression and consequent hyporesponsiveness to IFN alpha raises the question of the usefulness of IFN alpha therapy in end-stage AIDS. The normal expression of IFN gamma receptors in AIDS patients suggests that IFN gamma may prove useful in attempts to provide immune reconstitution.

Histo- and immunopathological features of terminal AIDS. An autopsy case of a Japanese man with neurological signs as initial symptoms

An autopsy case of a 37-year-old Japanese man, confirmed as an AIDS patient infected by an undetermined route of transmission, is presented. The initial symptoms of full-blown AIDS in this case were neurological, and the patient died of severe pneumonia 9 months after onset. The main histo- and immunopathological features were a marked depletion of helper-inducer T cells and dendritic reticulum cells in the lymphoid tissues, opportunistic infections, and some neuropathologic changes. Very few cells, possibly macrophages, immunoreactive with a monoclonal antibody (VAK-5) against HIV-gag protein P24 were found in the mediastinal lymph nodes. Numerous pathogens had induced opportunistic infections in many organs: severe and generalized cytomegalovirus infection, Pneumocystis carinii pneumonia, bronchopneumonia (possibly due to Pseudomonas aeruginosa), candidiasis in the tongue and oral cavity, and atypical mycobacteriosis in the pulmonic hilar lymph nodes. Vascular proliferation was found in the perinodal regions of some lymph nodes, but this was not neoplastic vascular proliferation compatible with that of localized Kaposi's sarcoma.

Parameters of production and partial characterization of feline interleukin 2

The conditions for the production of feline interleukin 2 (IL-2) from peripheral blood leukocytes (PBL) and splenocytes by concanavalin A (Con A) stimulation are described. Feline IL-2 was quantitated by measuring DNA synthesis in the murine IL-2-dependent cell line, CTLL-20. In addition, feline IL-2 was generated for the maintenance of long-term cultures of Con A-stimulated feline PBL and for biochemical characterization. Finally, IL-2 production was evaluated from the PBL of feline leukemia virus (FeLV)-infected cats. Con A at 9.6 micrograms/ml produced a plateau of peak IL-2 activity from 24 to 48 h following stimulation. The tumor promoter, phorbol myristic acetate, stimulated feline IL-2 production and enhanced Con A-stimulated feline IL-2 production. Fetal calf serum (FCS) was not required for IL-2 production; however, FCS at 5% (v/v) allowed for maximal Con A-stimulated IL-2 production. Feline IL-2 generated from Con A-stimulated splenocytes migrated with an apparent molecular size of 13.7 to 23 kD by gel filtration chromatography and supported the proliferation of Con A-activated feline PBL at a final concentration of 0.3 to 0.9 units/ml.

In vitro activation of T lymphocytes from HIV-seropositive blood donors. II. Decreased mitogen-induced expression of interleukin 2 receptor by both CD4 and CD8 cell subsets

Mononuclear cells (MC) from many individuals exposed to human immunodeficiency virus (HIV) exhibit a reduced proliferative response to a suboptimal concentration of phytohemagglutinin (PHA). However, the relative contributions of the 2 major T-cell subsets, namely CD4 and CD8 lymphocytes, to this reduced response remain unclear. Based on reports that interleukin 2 receptor (IL2R) expression correlates well with proliferative responses in HIV infection, we used dual-color cytofluorometry to measure IL2R expression by CD4 and CD8 cells following PHA activation of MC from HIV-seropositive blood donors. For data analysis, this study group was divided into two subgroups on the basis of DNA synthesis responses (seropositive with normal DNA synthesis, designated sero + NML, or seropositive with decreased DNA synthesis, designated sero + LOW). When compared to the seronegative control and sero + NML groups, the sero + LOW group exhibited significant reductions in the percentage of MC expressing IL2R, the proportion of CD4 cells expressing IL2R, and the proportion of CD8 cells expressing IL2R. In contrast, these parameters were unchanged in the sero + NML group compared to the control group. These findings show that reduced PHA-induced proliferative responses by MC from HIV-infected persons are associated with decreased IL2R expression by both CD4 and CD8 lymphocyte subsets.

Clinical and immunologic aspects of FeLV-induced immunosuppression

Cats exposed to the feline leukemia virus (FeLV) may mount an effective immune response and eliminate the virus, develop a non-viremic, latent infection or become persistently infected and shed the virus. Persistently infected cats commonly die of secondary opportunistic infections that result from FeLV-induced immunosuppression. The acquired immunosuppression is the most frequent and most devastating consequence of FeLV infection in the cat. Immunosuppression is targeted primarily to the cell-mediated immune system and has been attributed to the viral p15e envelope protein. The decreased IgG response and proliferative response to T cell mitogens is thought to be due to a defect in the helper cell function. As a result of T helper cell immunosuppression, infected cats may also have defective cytotoxic lymphocyte and activated macrophage functions which are regulated by their lymphokines. Research has shown that the virus causes a general suppression in the production of T cell-derived lymphokines, including gamma interferon and interleukin 2. A decrease in the function of polymorphonuclear leukocytes has also been reported and may contribute to deaths due to opportunistic infections in FeLV-positive cats. There are numerous parallels between the acquired immunodeficiency syndrome (AIDS) in man and the FeLV-induced immunodeficiency syndrome in cats. Frequent deaths due to opportunistic infections, lymphopenia, depressed cell-mediated immune responses to T cell-dependent antigens despite hypergammaglobulinemia and the presence of a long period of time between infection and the onset of clinical signs are just a few of the syndromes that are similar between the 2 retroviral diseases. A new strain of FeLV, FeLV-FAIDS has been associated with a naturally occurring immunosuppressive syndrome that is strikingly similar to AIDS in man. In addition, a T-lymphotropic retrovirus has recently been identified from cats with an immunodeficiency-like syndrome; this feline lentivirus disease is morphologically similar, but antigenically distinct from the human immunodeficiency virus, the cause of AIDS. Treatment for FeLV immunosuppression is primarily supportive. The development of a soluble tumor cell antigen vaccine has been shown to be efficacious in preventing FeLV infections.

Defect in lectin-induced interleukin 2 production by peripheral blood lymphocytes of patients with invasive urinary bladder carcinoma

The production of interleukin 2 (IL-2) by phytohaemagglutinin (PHA)-stimulated peripheral blood mononuclear cells (PBMC) from 21 patients with transitional cell carcinoma of the urinary bladder (BTCC) and 16 control blood donors was measured with a solid phase enzyme immunoassay based on the dual antibody immunometric sandwich principle. PBMC from patients with invasive BTCC (grade III-IV) showed a defect in the production of IL-2. The concentration of IL-2 in the supernatants of PBMC cultures from these patients was substantially lower (0.4 +/- 0.1 U/ml) than that observed in the supernatants of PBMC cultures from patients with non-invasive BTCC, grade II (1.5 +/- 0.7 U/ml), and from tumour-free controls (1.4 +/- 0.8 U/ml). These results suggest an immune dysfunction based on quantitatively impaired IL-2 production in patients with invasive BTCC and indicate that exogenous IL-2 could be used as an immunological response modifier for the treatment of these patients.