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Biomedical subjects

A R Hayward

Publications and source records attributed to A R Hayward.

At least 55 records · Page 3Linked to original sources

Major histocompatibility complex restriction of T-cell responses to varicella-zoster virus in guinea pigs.

Varicella-zoster virus (VZV), adapted to grow in guinea pig fibroblasts, was injected subcutaneously into Hartley, strain 2, and strain 13 guinea pigs. Serum immunoglobulin G antibodies were detected 2 weeks later, and T-cell proliferative responses by blood lymphocytes were found 3 weeks after injection. The proliferating cells bound the 155 antibody, which defines a CD4-like subset of guinea pig T lymphocytes. VZV-infected fibroblasts of human, Hartley, and strain 13 origin elicited equivalent amounts of proliferation, which was quantitatively greater than that obtained with an extracted VZV antigen. Uninfected (control) human or guinea pig fibroblasts did not elicit T-cell proliferation. The proliferative response to VZV required the presence of autologous (strain 2 or 13) antigen-presenting cells and was blocked by the addition of an anti-class II major histocompatibility complex antibody. Effector cells obtained from in vitro cultures mediated class II-restricted cytotoxicity to L2C cells incubated with VZV. Class I-restricted responses were obtained only by cross-priming strain 2 animals with strain 13 peritoneal exudate cells which had been preincubated with VZV. The data indicate that guinea pigs resemble humans in that class II-restricted T cells with specificity for VZV are more readily cultured from blood than are class I-restricted cells.

Animals↗

T cell proliferative response to interleukin 2: different frequency of responders among CD45R0 and CD45RA subsets.

A proportion of human blood T cells is known to proliferate in cultures containing 10 or more units/ml of interleukin (IL)2, in the absence of exogenously added antigen. A possible explanation for this phenomenon is that the IL2 serves to maintain the proliferation of memory T cells which have recently been activated by antigen in vivo. To test this possibility we therefore separated T cells according to their CD45 (common leukocyte antigen) phenotype into the CD45RO and CD45RA subsets which are associated with memory and naive status, respectively. The frequency of responder cells in limiting dilution analysis of adult MNC was 1:1625 CD45RO cells, 1:2405 for CD45RA cells, and 1:1642 for unseparated cells. CD45RA cells from newborns had a 1:1850 frequency of responders. The IL2 responder cells were predominantly CD3+ TcR alpha beta +, with a minor component of TcR delta cells. There were no differences in the frequency of T cells using V beta 5 and V beta 8 between responding and nonresponding cells. The data argue against a requirement for prior sensitization for a proliferative response to IL2 and give no evidence that the subset of T cells which responds to IL2 differs in phenotype from nonresponsive cells.

Adult↗

V beta 5 and V beta 8 memory T cells in adults and infancy: co-ordinated increase in response to early antigen stimulus.

Blood mononuclear cells (MNC) expressing the T cell receptor V beta gene families were identified with the monoclonal antibodies 1C1 (V beta 5) or Mx6 (V beta 8). These cells were typed for expression of the T200 common leucocyte antigen with the CD45RA antibody defining the 220-kD variant (which characterizes naive cells) and the UCHL1 antibody which defines the 180-kD variant (characterizing memory cells). Of adult MNC, 3 +/- 0.44% stained for V beta 5 and 4.12 +/- 0.26% stained for V beta 8; similar results were obtained in a group of infants aged less than 3 months, who were exposed to antigen stimulus in the form of infection and/or blood transfusion. While the total percentages of V beta 5 and V beta 8 cells in the blood of adults were not correlated, the proportions of these cells expressing CD45RO was positively correlated. A similar trend which did not reach statistical significance was present in a group of infants. A minority of the infants studied showed transient deviations from the mean established for adults. The results suggest that naive and memory T cell populations have similar frequencies of V beta 5 and V beta 8 expressing cells, and that age does not affect the frequency of usage of either of these V beta families.

Adult↗

T-cell responses to predicted amphipathic peptides of varicella-zoster virus glycoproteins II and IV.

Four peptides from the predicted amino acid sequences of varicella-zoster virus (VZV) glycoproteins II and IV selected for potential amphipathicity and a terminal lysine residue were synthesized. The peptides elicited weak proliferative responses by T cells with the CD4+ UCHL1+ CD45R- phenotype from the blood of VZV-immune individuals. The frequency of responder cells in individuals with specific response to peptides was 1:80,000 or fewer blood mononuclear cells, and the number of peptides responded to did not correlate with the proliferative response to VZV antigen. Of 40 peptide-specific T-cell clones obtained by limiting dilution, 10 were restimulated by extracted VZV antigen in the presence of autologous antigen-presenting cells. A total of 50% of these clones lysed HLA class II-positive lymphoblasts which had been preincubated with the appropriate peptide, and 2 of 15 cytotoxic clones lysed lymphoblast targets superinfected with VZV. The data indicated that T cells with specificity for putative VZV peptides may readily be cultured from the subset of blood mononuclear cells which bears the phenotype associated with memory.

Adult↗

Neonatal injection of CD3 antibody into nonobese diabetic mice reduces the incidence of insulitis and diabetes.

Over 80% of nonobese diabetic (NOD) mice develop lymphocytic infiltrates of their pancreatic islets (insulitis) by 6 wk of age and 50% of the females are diabetic by 6 mo of age. The incidence of insulitis in NOD mice injected once as neonates with 250 micrograms of the CD3 antibody, 145.2C11, was 8% at 10 wk of age, increasing to 25% at 32 wk of age. Fewer than 10% of these animals developed diabetes by 8 mo of age. Neonatal administration of 145.2C11 reduced the proliferative responses of spleen cells to mitogen stimulation 2 and 4 wk postinjection and expression of TCR was reduced 1 to 5 wk postinjection. The percentage of CD4 and CD8 cells in the spleen was transiently reduced after injection and the frequency of Pgp-1+-high cells (putative memory cells) was increased 2 to 4 wk postinjection, suggesting that in vivo administration of the antibody caused some T cells to divide as well as transiently reducing T cell numbers. IL-2R expression was not detected on spleen cells in the 4 wk after antibody injection. The phenotypic and functional changes after neonatal CD3 antibody injection resolved by 8 wk of age. The control and injected mice grew normally and made equivalent IgG antibody responses to injected human IgG. Neonatally injected 145.2C11 antibody was cleared from the circulation with a terminal half-life approximating to 21 days but greater than 90% of antigen binding activity was lost 6 days after injection. Protection from diabetes did not follow neonatal elimination of T cells with CD4 and CD8 antibodies, nor the injection of a TCR subset antibody, F23.1. Our data suggest that the neonatal T cell repertoire is open to modulation by a single injection of a CD3 antibody and they offer a new experimental approach to immunotherapy in an animal model of type 1 diabetes.

Animals↗

Ontogeny of expression of UCHL1 antigen on TcR-1+ (CD4/8) and TcR delta+ T cells.

The frequency of blood mononuclear cells expressing the 180-kDa splice variant of the common leukocyte antigen identified by the UCHL1 monoclonal antibody (a characteristic of post-thymic cells which have been through a cycle of stimulation) rose in a logarithmic relationship to age between birth and 16 years. At birth only a low frequency of CD4+ (negative for CD 25) and no CD8+ T cells expressed UCHL1. The subsequent increase in UCHL1 expression occurred in parallel on T cells expressing alpha/beta receptors and gamma/delta receptors, suggesting that these subsets participated in post-thymic proliferation in proportion to their numbers in blood. The frequency of UCHL1 expression on CD8 cells was 5-15% less than on CD4 cells.

Age Factors↗

Inhibition of varicella-zoster virus in vitro by human peripheral blood mononuclear cells.

A functional in vitro assay of cell-mediated immunity to varicella-zoster virus (VZV) is described. This procedure uses an enzyme-linked immunosorbent assay (ELISA) to measure the inhibitory effect of human peripheral blood mononuclear cells on VZV antigen production by VZV-infected cell monolayers. When mononuclear cells from VZV-immune, tetanus-immune donors were stimulated with either VZV antigen or tetanus toxoid they reduced VZV antigen production. In contrast, mononuclear cells from VZV-nonimmune, tetanus-immune donors reduced VZV antigen only when stimulated with tetanus toxoid, but not when stimulated with VZV antigen. Cell-free supernatants recovered from the VZV inhibition assays contained the anti-VZV activity. The magnitude of the anti-VZV activity of the supernatants equalled the inhibition observed when the stimulated mononuclear cells were added to the VZV-infected monolayers. Treatment of either mononuclear cells or supernatants with anti-interferon gamma antibody indicated that their VZV inhibitory capability was largely due to the production of interferon gamma by stimulated mononuclear cells.

Adult↗

A cytotoxic monoclonal islet cell surface antibody from the NOD mouse.

Monoclonal antibody (Mab) 1.93B7 was obtained by fusion of spleen cells from a diabetic NOD mouse with P3X63Ag8.653 myeloma cells and screening for complement mediated lysis of rat insulinoma (RIN) cells. Immunofluorescence studies revealed that this Mab binds to RIN cells but not to the rat pituitary tumour line GH3. The binding of Mab 1.93B7 to RIN cells was abolished by trypsin but not by neuraminidase treatment of the cells, suggesting that the antigen recognized is a protein. Mab 1.93B7 bound to approximately 30% of mouse (BALB/c) and rat islet cells which had been subjected to trypsin digestion and incubated as a single cell suspension for 12h to allow reexpression of trypsin sensitive antigens. Since Mab 1.93B7 is potentially pathogenic, as suggested by its reactivity to primary islet cells and its complement fixing capacity, we injected it into BALB/c and NOD mice. Cytotoxic activity against RIN cells was detected in the serum of the animals injected with Mab 1.93B7, but the Mab did not exert a diabetogenic action and failed to reverse diabetes when administered at onset in NOD mice. No modification of the course of spleen cell mediated transfer of diabetes in NOD mice was observed when the Mab was administered from the time of spleen cell inoculation to the appearance of glycosuria. The implications of the lack of an effect in vivo of Mab 1.93B7 under the conditions employed are discussed.

Animals↗

Nicotinamide protects target cells from cell-mediated cytolysis.

Nicotinamide in concentrations of 5 mM and greater protected fibroblast target cells from lysis by lymphokine-activated killer cells (LAK cells). Protection was concentration dependent and was exerted at the level of the target cell. Nicotinamide did not interfere with effector-target cell conjugate formation or with the calcium dependent triggering step of the lytic process. Target cell lysis in cultures without nicotinamide was accompanied by fragmentation of target cell DNA. The DNA of target cells cultured with LAK cells in the presence of nicotinamide remained intact. 3-Aminobenzamide which, like nicotinamide, inhibits poly(ADP-ribose) synthetase but is not a precursor of NAD, was an effective inhibitor of target cell lysis while nicotinic acid, an alternative precursor of NAD in cells, was not. The data point to a central role for poly(ADP-ribose) synthetase in the events leading up to DNA fragmentation and the release of 51Cr from target cells damaged by lymphokine-activated killer cells.

Benzamides↗

Human tonsillar IgE biosynthesis in vitro. II. Analysis of T cell regulation with monoclonal antibodies.

Phenotypes of T cells regulating human tonsillar IgE biosynthesis in vitro were studied by use of Leu 2a and Leu 3a monoclonal antibodies that recognize T cell subsets. B cells cultured with Leu 3a+-enriched populations (B cells plus T3a) produced significantly more IgE and IgG in the presence of pokeweed mitogen than B cells with the Leu 2a+-enriched populations (B cells plus T2a) (p less than 0.001 for IgE and p less than 0.001 for IgG). No significant differences were observed in IgE and IgG synthesis between the cultures of B cells alone and B cells plus T2a. T2a, but not T3a cells, significantly suppressed IgE synthesis (p less than 0.05 for geometric means and p less than 0.001 for percent suppression) when the cells were added to cultures of B cells plus T3a. Suppression of IgG synthesis was not observed under conditions that suppressed IgE synthesis, suggesting qualitative and quantitative differences in regulation of production of these isotypes. When T2a cells were irradiated, the suppressor activity disappeared. When graded numbers of T3a cells were added to B cells, it was noted that IgE synthesis first increased and then decreased as the numbers of T3a were increased. When the T3a cells were irradiated, IgE biosynthesis was suppressed at lower T/B ratios (less than 1 in four of five experiments) and was enhanced at higher T/B ratios (greater than 1 in all five experiments). Similar results were observed in experiments with OKT4 and OKT8 monoclonal antibodies. It is concluded that phenotypes of helper T cells for IgE synthesis are Leu 3a+ or OKT4+ and that IgE suppressors are predominantly Leu 2a+ or OKT8+ and are radiosensitive, as reported for regulation of other isotypes. However, it is suggested that Leu 3a+ and OKT4+ cells consist of radioresistant and radiosensitive helper cells and, presumably, a minor population of suppressor cells.

Antibodies, Monoclonal↗

Delay in onset of insulitis in NOD mice following a single injection of CD 4 and CD 8 antibodies.

Non-obese diabetic (NOD) mice injected with 500 micrograms of both CD 4 and CD 8 antibodies at 5 weeks of age did not develop insulitis until 18 weeks of age, 12 weeks later than the onset of insulitis in parallel uninjected controls. Injection with both antibodies at 2 weeks or 4 weeks of age protected from insulitis for 10 and 14 weeks respectively. Insulitis was not delayed in onset in animals injected at any age with one antibody only, or who were injected at birth. Injection after the onset of insulitis achieved partial but incomplete clearing of islet infiltrates. Salivary gland infiltrates (sialitis) were also delayed in animals injected with both CD 4 and CD 8 antibodies though the degree of protection was less pronounced than that seen for insulitis.

Age Factors↗

Acute renal failure--10-year experience of the Johannesburg Hospital renal unit.

The 10-year experience of Johannesburg Hospital's renal unit in treating acute renal failure (ARF) is described; 290 patients were treated by haemodialysis--169 drawn from the surgical disciplines, 109 from the medical disciplines and 12 from obstetrics and gynaecology, suffering 55%, 41% and 33% mortality rates, respectively. The mortality rates were found to correlate strongly with the cumulative number of acute insults to renal function accruing as a result of the particular surgical or medical illness ('precipitating event') and culminating in ARF. Age was also shown to have a powerful influence on outcome, the survival rate falling steadily with each decade of life. A plea is made to limit the potential insults to renal function actively, particularly in the elderly, in an attempt to further reduce the high mortality rate with which ARF continues to be stubbornly associated.

Acute Kidney Injury↗

Lymphocyte responses to varicella zoster virus in the elderly.

Elderly subjects (age 75-95 years) immune to varicella zoster virus (VZV) were identified by the presence of serum IgG antibody. The frequency of lymphocytes in their blood which proliferated in varicella zoster virus antigen-stimulated cultures was 1:78,000 +/- 6600. This is less than the 1:14,000 +/- 2000 frequency of VZV-responsive lymphocytes in blood from younger adult (20-43 years) donors. Elderly donors' blood mononuclear cells were less efficient than those of younger adults at lysing VZV-infected fibroblasts but not K562 target cells. The lysis of VZV target cells by elderly donors' MNC increased to control levels in the presence of 10 U/ml of interleukin-2 (IL-2). These results suggest that mononuclear cells capable of killing VZV-infected target cells persist with aging but that reduced numbers of antigen-responsive and lymphokine-releasing T cells may limit their function.

Aged↗

Varicella-zoster virus infection of human mononuclear cells.

Varicella-zoster virus (VZV) DNA was detected in mononuclear cells (MNC) of 7 humans with acute zoster 1-23 days after the onset of skin lesions. To further study the interaction of VZV with human MNC, cells obtained from seropositive normal donors were infected with VZV and analyzed for the presence of viral DNA and proteins. VZV-DNA was detected in T, B, and OKM 1 (monocyte-macrophage) positive cells, and virus-specific proteins were demonstrated by indirect immunofluorescence and immunoprecipitation. Hybridization studies revealed that VZV-DNA did not replicate in human MNC.

Adult↗

Processing and presentation of cell-associated varicella-zoster virus antigens by human monocytes.

To determine whether viral antigens associated with infected cells were processed for presentation to T cells, we cultured human blood mononuclear cells (MNC) from varicella-zoster virus (VZV) immune donors with VZV-infected fibroblasts of known HLA type which had been fixed in 0.05% glutaraldehyde. After 7-8 days of culture thymidine uptake by T4+ cells exceeded that of T8+ cells. Stimulated cells were depleted of adherent cells and restimulated with VZV-infected fibroblasts from donors matched or unmatched with the responder for HLA type in the presence or absence of fresh adherent cells. Proliferation of the VZV-specific blasts required the presence of adherent cells matched with the responder lymphocytes for HLA-DR; conversely, the VZV specific response was not restricted by the MHC of the fibroblasts used in the restimulation assay. Preincubation of the adherent cells with chloroquine inhibited the proliferative response in a dose-dependent manner. These results suggest that VZV antigens on infected cells may be processed by monocytes for presentation to T cells.

Adult↗