Seroprevalence of Mycoplasma bovis in bulk milk samples in Irish dairy herds and risk factors associated with herd seropositive status

Mycoplasma bovis is a serious disease of cattle worldwide; mastitis, pneumonia, and arthritis are particularly important clinical presentations in dairy herds. Mycoplasma bovis was first identified in Ireland in 1994, and the reporting of Mycoplasma-associated disease has substantially increased over the last 5 years. Despite the presumed endemic nature of M. bovis in Ireland, there is a paucity of data on the prevalence of infection, and the effect of this disease on the dairy industry. The aim of this observational study was to estimate apparent herd prevalence for M. bovis in Irish dairy herds using routinely collected bulk milk surveillance samples and to assess risk factors for herd seropositivity. In autumn 2018, 1,500 herds out of the 16,858 herds that submitted bulk tank milk (BTM) samples to the Department of Agriculture testing laboratory for routine surveillance were randomly selected for further testing. A final data set of 1,313 sampled herds with a BTM ELISA result were used for the analysis. Testing was conducted using an indirect ELISA kit (ID Screen Mycoplasma bovis). Herd-level risk factors were used as explanatory variables to determine potential risk factors associated with positive herd status (reflecting past or current exposure to M. bovis). A total of 588 of the 1,313 BTM samples were positive to M. bovis, providing an apparent herd prevalence of 0.45 (95% CI: 0.42, 0.47) in Irish dairy herds in autumn 2018. Multivariable analysis was conducted using logistic regression. The final model identified herd size, the number of neighboring farms, in-degree and county as statistically significant risk factors for herd BTM seropositivity to M. bovis. The results suggest a high apparent herd prevalence of seropositivity to M. bovis, and evidence that M. bovis infection is now endemic in the Irish dairy sector. In addition, risk factors identified are closely aligned to what we would expect of an infectious disease. Awareness raising and education about this important disease is warranted given the widespread nature of exposure and likely infection in Irish herds. Further work on the validation of diagnostic tests for herd-level diagnosis should be undertaken as a matter of priority.

Significant re-emergence and recirculation of Schmallenberg virus in previously exposed dairy herds in Ireland in 2016

Schmallenberg virus (SBV) circulation was investigated in 25 previously exposed dairy herds in Ireland in 2016. A population of 1,550 spring-2014-born animals, which had been monitored for SBV infection in 2014 and 2015 as part of a previous SBV surveillance study, were resampled for evidence of SBV infection during 2016. A total of 366 blood samples were collected in the 25 study herds (15 samples per herd) between 3 March 2017 and 10 March 2017 (before the 2017 vector-active season) and analysed for SBV antibodies using a competitive ELISA kit (IDVet). A total of 256 animals tested seropositive, an AP of 69.9% (95% CI: 65.1-74.4) and TP of 77.7% (95% CI: 72.3%-82.8%) when correcting for imperfect test characteristics. These results demonstrate that a new epidemic of SBV circulation occurred in these previously exposed herds in Ireland in 2016.

Offsetting the impacts of mining to achieve no net loss of native vegetation

Offsets are a novel conservation tool, yet using them to achieve no net loss of biodiversity is challenging. This is especially true when using conservation offsets (i.e., protected areas) because achieving no net loss requires avoiding equivalent loss. Our objective was to determine if offsetting the impacts of mining achieves no net loss of native vegetation in Brazil's largest iron mining region. We used a land-use change model to simulate deforestation by mining to 2020; developed a model to allocate conservation offsets to the landscape under 3 scenarios (baseline, no new offsets; current practice, like-for-like [by vegetation type] conservation offsetting near the impact site; and threat scenario, like-for-like conservation offsetting of highly threatened vegetation); and simulated nonmining deforestation to 2020 for each scenario to quantify avoided deforestation achieved with offsets. Mines cleared 3570 ha of native vegetation by 2020. Under a 1:4 offset ratio, mining companies would be required to conserve >14,200 ha of native vegetation, doubling the current extent of protected areas in the region. Allocating offsets under current practice avoided deforestation equivalent to 3% of that caused by mining, whereas allocating under the threat scenario avoided 9%. Current practice failed to achieve no net loss because offsets did not conserve threatened vegetation. Explicit allocation of offsets to threatened vegetation also failed because the most threatened vegetation was widely dispersed across the landscape, making conservation logistically difficult. To achieve no net loss with conservation offsets requires information on regional deforestation trajectories and the distribution of threatened vegetation. However, in some regions achieving no net loss through conservation may be impossible. In these cases, other offsetting activities, such as revegetation, will be required.

Sensitivity of host-seeking nymphal lone star ticks (Acari: Ixodidae) to immersion in heated water

Host-seeking nymphal Amblyomma americanum (L.) (Acari: Ixodidae) were placed into heated water, and their survival or their torpidity was recorded as a function of exposure time. Exposures were determined that either kill the nymphs or affect their mobility. All nymphs died when exposed for a minute or more to a temperature > 51 degrees C. Nearly all nymphs remained motionless for a period of time when exposed for 3 min to a temperature > 44 degrees C.

A Study of Dry Cow Therapy and Effects on SCC in 10 Irish Dairy Herds

Somatic cell count (SCC) data for 480 cows in 10 Irish dairy herds from January 2001 until June 2002 were analysed. Herds were selected on the basis of a recent or ongoing history of clinical or subclinical mastitis. An individual cow SCC of 200 000 cells per ml was used as the threshold for elevation of SCC. The duration of elevated SCC prior to drying-off and the magnitude of the elevation in SCC were found to have an impact on the response to dry cow therapy (DCT). A trend also emerged indicating that increasing parity had a negative influence on the response to DCT.

Reflexive shifts of covert attention operate in an egocentric coordinate frame

Covert shifts of attention have been shown to improve detection and discrimination thresholds for a range of visual stimuli. Although there is some evidence to suggest that the allocation of attention to a particular region of interest occurs in a retinotopic frame of reference, the importance of an allocentric, or object-based, framework has gained widespread empirical support. The current experiment investigates the nature of the spatial representation in which covert shifts of attention occur in response to a reflexive prime. Primes and targets were presented in four conditions designed to vary systematically the validity of the spatial relationship between the prime and target in egocentric or allocentric coordinate frameworks. A significant advantage, in terms of reaction time and correct identification, was found for targets located in positions previously primed in an egocentric (but not allocentric) framework whereas there was no advantage for locations primed in an allocentric (but not egocentric) framework. These results suggest that the allocation of covert spatial attention within an egocentric framework may be more important than previously thought.

Analysis of intensive care populations to select possible candidates for high dependency care

OBJECTIVES

To identify the proportion, and range across intensive care units, of intensive care patients who might potentially be managed on a high dependency unit (HDU) using three different classification systems.

METHODS

8095 adult patients admitted to 15 intensive care units in the south of England between 1 April 1993 and 31 December 1994 were studied. Patients were identified as potential HDU admissions if their APACHE III derived risk of hospital mortality was < or =10%, if they were categorised as a low risk monitor (LRM) patient using the Wagner risk stratification method, or if they did not require advanced respiratory support (ARS).

RESULTS

4146 patients (51.2%) had an APACHE III derived risk of hospital death of < or =10%, 1687 (20.8%) were classified as LRM, and 3860 (47.7%) did not receive ARS. The values for each intensive care unit ranged from 32.8-63.3% (APACHE III group), 7.2-29.9% (LRM group), and 14.4-68.2% (ARS group). No matter which of the three methods was used, there were significant differences between the 15 units (p<0.0001) with regard to the number of potential HDU patients identified within the scored population.

CONCLUSIONS

The percentage of intensive care patients who might be more appropriately managed in a HDU varies considerably between hospitals, and depends upon both local circumstances and the method used to define a high dependency patient. However, whichever method is used, it appears that significant numbers of patients of low dependency status currently fill intensive care beds in the units studied. If these analyses are correct, the perceived national shortage in intensive care beds might be improved by the development of HDUs.

Sensitization of multidrug-resistant human leukemia cells with MDR1-targeted antisense and inhibition of drug-mediated MDR1 induction

Increased expression of MDR1 is strongly implicated in the appearance of chemotherapeutic drug resistance in cancer, especially hematological malignancies. We therefore examined the potential of antisense oligonucleotides to inhibit MDR1 and restore sensitivity to drug-resistant human lymphoblastic cells (CCRF-CEM). Treatment with two different phosphorothioate-modified antisense sequences as well as a DNA-RNA hybrid sequence resulted in a 30 to 45% decrease in MDR1 expression as determined by staining with the monoclonal antibody MRK16 followed by flowcytometry (FCM) analysis. Further, inhibition of MDR1 expression persisted for 3 days after removal of oligonucleotides. Increased accumulation of rhodamine 123 and nearly a three-fold sensitization of cells to vincristine paralleled the reduction in staining with MRK16. Reversed or scrambled control sequences had no effect in any of the assays. During the course of these studies, we observed a 25 to 75% increase in MRK16 staining of cells treated with the chemotherapeutic agents daunorubicin and vincristine as well as by the resistance reversal agents verapamil and cyclosporin. Treatment of cells with antisense oligonucleotides prior to exposure to daunorubicin or cyclosporin reduced the increase in MRK16 staining. These results indicate that antisense targeted to MDR1 can sensitize drug-resistant leukemia cells and suggest that antisense treatment may prevent the emergence of MDR1-mediated drug resistance.

Hsp90-mediated folding of the lymphoid cell kinase p56lck

Several lines of evidence suggest that members of the 90-kDa family of heat shock proteins (hsp90) may support the folding of various homologues of the src kinase family. In this work, we utilized pulse-chase analyses in rabbit reticulocyte lysate to demonstrate that hsp90-bound intermediates existed for the majority of newly synthesized p56lck molecules. The hsp90-binding drug geldanamycin disrupted the association of p56lck with hsp90, prevented the kinase from demonstrating a protease-resistant conformation, and caused decreases in kinase specific activity. Requirements for geldanamycin-inhibitable hsp90 function and physical interactions between hsp90 and p56lck persisted during chase periods. Consistent with the effects observed in rabbit reticulocyte lysate, application of geldanamycin to fibroblasts caused specific reversion of lck-mediated transformation concomitant with loss of p56lck activity and protein. However, geldanamycin had no direct effect on purified p56lck. Also consistent with functional linkages between hsp90 and p56lck, physical interactions between these proteins were detected in cytoplasmic, but not membrane, fractions of LSTRA cells. Although hsp90 functions in both the initial de novo folding and the reiterative support of p56lck structure in rabbit reticulocyte lysate, the specific occurrence of complexes between hsp90 and p56lck in the cytoplasm of T cells suggests that hsp90 primarily folds nascent molecules of p56lck in vivo.

The outcome of poliovirus infections in K562 cells is cytolytic rather than persistent after hemin-induced differentiation

K562-Mu erythroleukemia cells readily establish a long-term persistent poliovirus infection characterized by continuous virus production in the absence of complete p220 cleavage and host translation shutoff (R. E. Lloyd and M. Bovee, Virology 194:200-209, 1993). The mechanism of resistance appears to be modulated at the intracellular level and to be related to decreased virus-mediated cytopathic effects (P. A. Benton, J. W. Murphy, and R. E. Lloyd Virology 213:7-18, 1995). It is well documented that hemin induces the differentiation of K562 cells and alters the expression of several host proteins. We report here that growth of K562 cells in hemin prior to poliovirus infection results in a dose-dependent increase in virus-induced cell lysis and thereby alters the normally persistent outcome of infection to a more lytic phenotype. K562 cells infected after hemin treatment displayed increased host translation shutoff, p220 cleavage, viral protein synthesis, and viral RNA accumulation compared with nontreated cells. Since hemin treatment of K562 cells also induced the increased expression of several heat shock proteins (Hsp70, Hsc70, Hsp90, and cohort p60), we tested the hypothesis that their increased expression may play a role in altering poliovirus infection in hemin-treated K562 cells. However, neither heat stress nor oxidative stress, inducers of heat shock protein synthesis, altered the outcome (of virus infections. In addition, we report the novel finding that subunits of two translation initiation factors, p220 (eIF-4G) and eIF-2alpha, are cleaved as a result of hemin treatment of K562 cells. It is proposed that hemin alters the expression of specific host proteins in K562 cells, probably other than heat shock proteins, which changes the initial response to poliovirus infections from persistent to lytic.

Arrested rearrangement of TCR V beta genes in thymocytes from children with X-linked severe combined immunodeficiency disease

Human X-linked severe combined immunodeficiency disease (SCID) is an immunodeficiency disorder in which T cell development is arrested in the thymic cortex. B lymphocytes in children with X-linked SCID seem to differentiate normally. X-linked SCID is associated with a mutation in the gene that encodes the IL-2R gamma-chain. Because TCR-beta gene recombination is a pivotal initial event in T lymphocyte ontogeny within the thymus, we hypothesized that a failure to express normal IL-2R gamma could lead to impaired TCR-beta gene recombination in early thymic development. PCR was used to determine the status of TCR-beta gene-segment rearrangements in thymic DNA that had been obtained from children with X-linked SCID. The initial step in TCR-beta gene rearrangement, that of D beta to J beta recombination, was readily detected in all thymus samples from children with X-linked SCID; in contrast, V beta to DJ beta gene rearrangements were undetectable in the same samples. Both D beta to J beta and V beta to DJ beta TCR genes were rearranged in the thymic tissues obtained from immunologically normal children. We conclude that TCR beta-chain gene rearrangement is arrested in children with X-linked SCID. Our results suggest a causative relationship between the failure of TCR beta-chain gene rearrangements to proceed beyond DJ beta rearrangements and the production of a nonfunctional IL-2R gamma-chain.

Arrested rearrangement of TCR V beta genes in thymocytes from children with X-linked severe combined immunodeficiency disease

Human X-linked severe combined immunodeficiency disease (SCID) is an immunodeficiency disorder in which T cell development is arrested in the thymic cortex. B lymphocytes in children with X-linked SCID seem to differentiate normally. X-linked SCID is associated with a mutation in the gene that encodes the IL-2R gamma-chain. Because TCR-beta gene recombination is a pivotal initial event in T lymphocyte ontogeny within the thymus, we hypothesized that a failure to express normal IL-2R gamma could lead to impaired TCR-beta gene recombination in early thymic development. PCR was used to determine the status of TCR-beta gene-segment rearrangements in thymic DNA that had been obtained from children with X-linked SCID. The initial step in TCR-beta gene rearrangement, that of D beta to J beta recombination, was readily detected in all thymus samples from children with X-linked SCID; in contrast, V beta to DJ beta gene rearrangements were undetectable in the same samples. Both D beta to J beta and V beta to DJ beta TCR genes were rearranged in the thymic tissues obtained from immunologically normal children. We conclude that TCR beta-chain gene rearrangement is arrested in children with X-linked SCID. Our results suggest a causative relationship between the failure of TCR beta-chain gene rearrangements to proceed beyond DJ beta rearrangements and the production of a nonfunctional IL-2R gamma-chain.

Persistence of multiple maternal genotypes of human immunodeficiency virus type I in infants infected by vertical transmission

The extent of nucleotide variation within the HIV-1 env hypervariable domains serves as a marker of virus genotypes within infected individuals and as a means to track transmission of the virus between individuals. We analyzed env V1 and V2 sequences in longitudinal samples from two HIV-1-infected mothers, each with three children infected by maternal transmission of the virus. Sequences in samples that were obtained from two infants at 2 d and 4 wk after birth displayed more variation in V1 and V2 than maternal samples obtained at the same times. Multiple HIV-1 genotypes were identified in each mother. In each family, multiple maternal HIV-1 genotypes were transmitted to the infants. Specific amino acid residues in the hypervariable domains were conserved within sequences from each family producing a family-specific amino acid signature pattern in V1 and V2. Viruses that were highly related to maternal viruses in signature pattern persisted for as long as 4 yr in the older children. Results support a model of transmission involving multiple HIV-1 genotypes with development of genetic variation from differential outgrowth and accumulation of genetic changes within each individual.

Independent variation and positive selection in env V1 and V2 domains within maternal-infant strains of human immunodeficiency virus type 1 in vivo

Multiple targets for immune recognition and cellular tropism are localized to the V1 and V2 hypervariable regions in the amino portion of human immunodeficiency virus type 1 (HIV-1) gp120env. We have assessed genetic diversity in env V1 and V2 hypervariable domains in vivo within epidemiologically related strains of HIV-1. Our strategy was to analyze longitudinal samples from two seropositive mothers and multiple children infected by perinatal transmission. Although the V1 and V2 domains are closely linked in the HIV-1 genome, nucleotide sequences in V1 and in V2 evolved independently in maternal-infant viruses in vivo. A high proportion of the nucleotide substitutions would introduce amino acid diversity in V1 and in V2. A significant excess of nonsynonymous over synonymous substitutions was identified in HIV-1 env V1 and V2 peptides in the mothers and in two older children but was not generally apparent in HIV-1 sequences in infants. An excess of nonsynonymous over synonymous substitutions indicated that there is positive selection for independent genetic variation in the V1 and V2 domains in vivo. It is likely that there are host responses to complex determinants in the V1 or V2 hypervariable domain of HIV-1 gp120.

Ocular manifestations of the lacrimo-auriculo-dento-digital syndrome

We studied a mother and daughter with an extremely rare constellation of signs and symptoms. One or both had absent lacrimal puncta, nasolacrimal duct obstruction, chronic dacryocystitis, dry eyes, and epiphora. Systemic findings included salivary gland hyposecretion, dental hypoplasia and dysplasia, cup-shaped ears with hearing loss, and digital anomalies. These findings are consistent with those of the lacrimo-auriculo-dento-digital syndrome, a genetic disorder. Our study supports the autosomal dominant inheritance of this syndrome, delineates the ophthalmic manifestations, and provides evidence that renal anomalies are part of the disorder.

The temporal association between gamma delta T cells and the natural history of insulin-dependent diabetes

We previously reported a significant increase in percentages of peripheral blood gamma delta+ T cells in islet cell antibody (ICA) positive relatives of patients with insulin-dependent diabetes (IDD). In the present study, we further characterized this T cell abnormality in a larger group of ICA+ subjects and report that (1) Percentages of gamma delta+ T lymphocytes were significantly increased only in subjects with high ICA titers (> or = 20 JDF units) (P = 0.005) and resulted from an increase in absolute numbers of gamma delta+ T lymphocytes. (2) In these subjects, the increase in gamma delta+ T lymphocytes was associated with an increase in the V gamma 9 V delta 2 subpopulation (r = 0.99). (3) In these same subjects, high percentages of gamma delta+ T lymphocytes were associated with normal beta cell function while low percentages were associated with diminished insulin response. Using 65 microU/ml as the threshold of abnormal intravenous glucose tolerance test (IVGTT) response, percentages of gamma delta+ T lymphocytes could significantly predict IVGTT status in these subjects (P < 0.01). A longitudinal follow-up further suggested that the development of an abnormal IVGTT response and progression to diabetes was associated with a decrease in percentages of gamma delta+ T lymphocytes while patients whose gamma delta+ T cell percentages remained high retained normal beta cell function. Our data therefore suggest that gamma delta+ T lymphocytes and more specifically V gamma 9 V delta 2 T cells are implicated in the autoimmune process leading to diabetes and may have a regulatory role. The monitoring of their percentages in the blood of patients at risk for diabetes may be useful as an additional predictor of diabetes development.

Corticosteroids improve survival of children with AIDS and Pneumocystis carinii pneumonia

OBJECTIVE

To determine if corticosteroids administered in addition to antimicrobials improve survival in children with acquired immunodeficiency syndrome and severe Pneumocystis carinii pneumonia (PCP).

DESIGN

Before-after, nonrandomized, case-comparison study.

SETTING

Pediatric intensive care unit of a tertiary care teaching hospital in Florida.

PARTICIPANTS

Eleven children infected with the human immunodeficiency virus (HIV) with confirmed PCP.

SELECTION PROCEDURE

Infants with HIV infection and acute respiratory failure due to PCP were studied sequentially.

INTERVENTION

The first seven infants were treated with antimicrobials alone while the next four received a 2-week course of methylprednisolone sodium succinate in addition to antimicrobials.

MEASUREMENTS AND RESULTS

The two groups were similar with respect to age, route of HIV infection, stage of HIV disease, CD4 T-cell count, antiretroviral therapy, and respiratory parameters at intubation. All children treated with antimicrobials alone died while receiving mechanical ventilation. Survival of the children who received corticosteroid therapy was significantly improved (P < .05), and all were weaned from the ventilator.

CONCLUSIONS

Corticosteroids administered in addition to antimicrobials and supportive care improve the short-term survival of HIV-infected children who have acute respiratory failure due to PCP.

Human anti-pneumococcal polysaccharide antibodies are secreted by the CD5- B cell lineage

To determine whether human antibody responses to T cell-independent pneumococcal polysaccharide antigens are derived from CD5+ or CD5- B cells, we utilized an ELISPOT assay to detect individual anti-polysaccharide antibody-secreting cells. Human anti-type IV pneumococcal polysaccharide antibody-secreting cells were found in the CD5- B cell subpopulation. An EBV transformed anti-pneumococcal antibody-secreting B cell line was also CD5-. The ontogeny of CD5 expressing B cells correlated with the age at which polysaccharide responsiveness is acquired (generally around age 2 years in humans). The CD5- B cell subset represents only 25-30% of the B cells in young children, but this fraction increases throughout childhood to a plateau of 70-80% of the B cells in adults. These results support the hypothesis that the developmental change in responsiveness to T cell-independent polysaccharide antigens in humans is associated with maturation of the CD5- B cell subset.

Increased T lymphocytes bearing the gamma-delta T cell receptor in subjects at high risk for insulin dependent diabetes

The effector mechanisms responsible for autoimmune beta cell destruction in insulin dependent (type 1) diabetes (IDD) remain elusive. In order to investigate whether T lymphocytes bearing the gamma-delta T cell receptor (gamma delta+ T cells) could be involved in this process, we measured percentages of peripheral blood gamma delta+ T cells in IDD patients, relatives of IDD probands and controls. High levels of gamma delta+ T cells strongly differentiated 23 relatives at high risk for IDD on the basis of positive islet cell autoantibodies (ICA positive relatives) from 59 controls (P = 0.0013), whereas 26 ICA negative relatives, 14 recent-onset and nine long term IDD patients could not be distinguished from controls on the basis of percentages of gamma delta+ T cells. These data suggest that increased levels of circulating gamma delta+ T cells correlate with the ongoing autoimmune process in pancreatic islets of subjects at high risk for IDD and may thus represent an additional marker for the development of the disease.

CD5+ B lymphocytes in high-risk islet cell antibody-positive and newly diagnosed IDDM subjects

Human CD5+ B lymphocytes produce autoantibodies that bind to self- and exogenous antigens. Extremely high percentages of CD5+ B lymphocytes are present in the fetal and newborn periods, whereas they constitute only a minority of B lymphocytes in healthy adults. Increased percentages of circulating CD5+ lymphocytes have previously been demonstrated in several autoimmune diseases, including rheumatoid arthritis, progressive systemic sclerosis, Graves' disease, and Sjögren's syndrome. We measured the percentages of B lymphocytes that expressed the CD5 determinant in 93 control subjects (age range 1 day to 59 yr, mean +/- 22.6 +/- 17.7 yr), 17 subjects with newly diagnosed insulin-dependent diabetes mellitus (IDDM; range 5-29 yr, mean +/- SD 13 +/- 5.9 yr), 31 high-risk islet cell antibody (ICA)-positive nondiabetic subjects (range 4-45 yr, mean +/- SD 19.8 +/- 14.1 yr), and 13 subjects with IDDM of greater than 5 yr duration (range 10-43 yr, mean +/- SD 24.2 +/- 9.9 yr). We report that CD5+ B-lymphocyte percentages are strikingly age dependent in healthy control subjects, declining progressively from the newborn period to the middle-age years (r = -0.75, P = 0.0001). In ICA+ nondiabetic and recent-onset IDDM subjects less than 29 yr of age, the percentage of circulating CD5+ B lymphocytes fell within the 95% confidence intervals established for control subjects. However, the age-dependent rate of decline in the percentage of CD5+ B lymphocytes within the control range was slower in ICA+ and newly diagnosed IDDM subjects than in control subjects.

Con A-induced suppressor cell function depends on the activation of the CD4+CD45RA inducer T cell subpopulation

Human T cells incubated for 48 hr with Con A suppress B cell Ig production. We sought to define the interactions between CD4+ T cells and CD8+ T cells in the generation of suppressor cell activity following Con A stimulation. Con A-activated CD4+ inducer T cells suppressed Ig production in autologous cocultures of T cells and B cells by 84%, while PHA-activated CD4+ T cells could not. However, Con A-activated CD4+ T cells are not themselves suppressors. When Con A-activated CD4+ T cells were added to coculture of B cells plus T cells depleted of CD8+ T cells, no suppression of Ig production was observed. Furthermore, these Con A-activated CD4+ T cells were able to provide excellent help for Ig production. Therefore, Con A-induced suppressor cell function requires a CD4+ suppressor/inducer acting on a CD8+ suppressor/effector ultimately resulting in the down regulation of B cell Ig synthesis. Human CD4+ inducer T cells can be functionally dissected into helper/inducer or suppressor/inducer T lymphocytes based on their expression of either the CDw29 or CD45RA surface molecules, respectively. Following incubation with Con A the expression of CD45RA on CD4+ T cells increased from 34 to 80% (P = 0.001) while CDw29 expression was unchanged. Incubating lymphocytes with PHA resulted in a non-specific increase in both CD45RA and CDw29 expression by CD4+ T cells. The increase in CD4+CD45RA expression was a result of active proliferation by the Con A-stimulated T cells. Suppression of Ig secretion was directly correlated with the enhanced CD45RA expression following Con A activation. We demonstrate that enhanced suppressor/inducer function is unique to Con A stimulation and was not observed following activation by PHA. Furthermore, short-term culture with Con A results in the selective expansion of the CD4+CD45RA T cell subpopulation.

Defective inducer T-cell function before the onset of insulin-dependent diabetes mellitus

To investigate the possible role of CD4+ T lymphocyte immunoregulatory abnormalities in the pathogenesis of human insulin-dependent diabetes mellitus (IDD), we studied the in vitro function of CD4+ helper/inducer and suppressor/inducer T-cell subpopulations in 25 high risk non-diabetic individuals who tested positive for islet-cell antibodies (ICA). Helper-inducer T-cell function, as measured in the pokeweed mitogen T-B co-culture system, was decreased in the ICA+ subjects in comparison to controls. This abnormality in helper/inducer T-cell function was present for both IgG (P = 0.0001) and IgM (P = 0.004) secretion by B cells. Diminished helper/inducer function correlated with ICA titer (Pearson correlation coefficient -0.44) with subjects having an ICA titer greater than or equal to 40 JDF units demonstrating the most significant disturbances in function (P = 0.01). The helper/inducer T-cell subset percentage was also decreased in ICA+ subjects when compared to matched controls (30 +/- 3% vs 39 +/- 2%; P = 0.02). The abnormality in helper/inducer function was intrinsic to the CD4+ CD45RA+ subset and was not simply due to diminished numbers of helper/inducer T-cells added in the co-culture experiments, since the defect persisted when CD4+ CD45RA+ helper/inducer T-cells were purified and added to B cells as the only source of T-cell help. Our results indicate that ICA+ subjects have functional defects in the helper/inducer subpopulation of CD4+ T-cells. This abnormality may contribute to the pathogenesis of IDD and may provide a novel marker for identifying persons at risk for developing IDD.

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.

Immunological applications of type III Fc binding proteins. Comparison of different sources of protein G

Protein G, a type III bacterial IgG Fc receptor isolated from certain group C or G streptococci, shows a wider range of species and subclass immunoglobulin reactivity than staphylococcal protein A and has been shown to be more useful than protein A for many immunochemical applications. Recently, two forms of wild type protein G and three forms of recombinant protein G have become commercially available. Each form of protein G was tested for reactivity with a variety of species of immunoglobulin and albumin. Additionally, one form of wild type protein G and two forms of the recombinant protein G were examined for their ability to stimulate in vitro proliferation of human peripheral blood leukocytes (PBL). Similar IgG species reactivity was observed for all forms of unlabeled protein G. By contrast, considerable variability in the relative IgG binding potentials of different protein G preparations was observed following radioiodination. Binding to human serum albumin was observed with one of the wild type protein G samples, however, the IgG binding activity of this protein was not affected by the presence of excess human serum albumin. In the human PBL proliferation assays, wild type protein G was weakly mitogenic and one form of recombinant protein G was shown to be a potent mitogen, while another form of recombinant protein G displayed no mitogenic potential. Differences in both functional and biological reactivities were observed among the various sources of protein G. These differences may lead to confusion if investigators consider all sources of protein G as a single entity with common properties.

Synthesis of an immunopathogenic fusion protein derived from a bovine interphotoreceptor retinoid-binding protein cDNA clone

We have extended the cDNA sequence of bovine interphotoreceptor retinoid-binding protein (IRBP) and subcloned one of the sequenced cDNA fragments into an expression vector. The nucleotide (nt) sequences of four bovine IRBP cDNA clones have been determined. These sequences when assembled cover the 3' proximal 3629 nt of the IRBP mRNA and encode the C-terminal 551 amino acids (aa) of IRBP. This cDNA sequence validates the intron: exon boundaries predicted from the gene. A 2-kb EcoRI insert from lambda IRBP2, one of the clones sequenced, encoding the C-terminal 136 aa of IRBP was subcloned into the expression vector pWR590-1. Escherichia coli carrying this plasmid construction, pXS590-IRBP, produced a fusion protein containing 583 N-terminal aa of beta-galactosidase, three linker aa residues, 136 C-terminal aa of IRBP and possibly a number of additional C-terminal residues due to suppressed termination. This 86-kDa fusion protein, purified by detergent/chaotrope extraction followed by reverse-phase high-performance liquid chromatography, cross-reacted with anti-bovine IRBP on Western blots. This protein induced an experimental autoimmune uveo-retinitis and experimental autoimmune pinealitis in Lewis rats indistinguishable from that induced by authentic bovine IRBP. Thus, it is evident that biological activity of this region of IRBP, as manifested by immuno-pathogenicity, is retained by the fusion protein.

Long-term immunoregulatory effects of therapy with corticosteroids and anti-thymocyte globulin

Corticosteroids and anti-thymocyte globulin (ATG) have been extensively used in the treatment of autoimmune diseases, aplastic anemia and organ graft rejection; nonetheless, the precise mechanisms of action of these agents are unknown. Studies of their long term immunoregulatory effects, particularly in humans, have been limited. We examined the long term effects of therapy with ATG given for 2-4 weeks and prednisone for 2 months in 4 patients with newly diagnosed insulin dependent diabetes (IDD). Three matched newly-diagnosed untreated IDD patients and 17 healthy volunteers served as controls. No differences in total lymphocyte count, percentage of B cells, percentage of total T cells (CD3), helper-inducer T cells (CD4) or cytotoxic-suppressor cells (CD8), lymphocyte blastogenesis assays, or pokeweed mitogen-induced IgG secretion in T & B cell co-cultures were detected before therapy. A transient lymphopenia following ATG administration was the only immunological defect found in the first month of therapy. At 2 months, however, patients treated with ATG and prednisone had diminished immunoregulatory T cell function demonstrated by production of only 28 +/- 3% IgG expected in T & B co-culture, compared to 205 +/- 35% for untreated IDD patients and 107 +/- 13% for normals (p less than 0.01). This diminished IgG production resulted from excessive suppressor function, since co-cultures of T cells from treated patients with T and B cells from normal volunteers suppressed the latter's IgG production by 76 +/- 9%. This enhanced suppressor activity persisted for 3-6 months following therapy. Other immunological functions were not statistically different from those present at the inception of the study. Thus, treatment with corticosteroids and ATG produces long-term enhanced suppressor activity, a finding which suggests that treatment with combination ATG and Prednisone is a rational form of immunomodulation in conditions associated with decreased suppressor function.

Genetic linkage analysis of autosomal dominant congenital cataracts with lens-specific DNA probes and polymorphic phenotypic markers

The authors studied a four-generation family with autosomal dominant congenital cataracts (ADCCs) using linkage analysis with 23 polymorphic phenotypic markers and DNA restriction fragment length polymorphisms (RFLPs) detected by lens-specific DNA probes. A total of 19 family members were studied and the ten affected members had embryonal lens opacities. Close linkage was rejected with DNA probes encoding beta-crystallin, gamma-crystallin, and the major intrinsic protein of the lens fiber membrane (MIP) excluding defects of these genes as the cause of the cataract in this family. No statistically significant lod scores were produced with the polymorphic phenotypic markers. These results support the genetic heterogeneity of ADCCs.

Polyclonal nature of islet cell antibodies in insulin-dependent diabetes

Islet cell antibodies (ICA) are associated with insulin-dependent diabetes mellitus (IDD) and have been proposed as predictive markers for the disease. To determine whether ICA result from the activation of single autoreactive B-lymphocyte clones or are the result of polyclonal B-cell activation, we assayed ICA using polyvalent antisera specific to kappa or lambda light chains as well as monoclonal antibodies to IgG1, IgG2, IgG3 and IgG4 heavy chains by indirect immunofluorescence. Sera from 38 newly diagnosed IDD patients with IgG-ICA titers greater than 1:8 by end-point dilution were studied. ICA of both kappa and lambda light chains were present in all sera. The ICA were predominantly of the IgG1 subclass (38/38), although ICA were also found to be IgG2 in 53% (20/38), IgG3 in 29% (11/38) and IgG4 in 16% (6/38). The distribution of IgG heavy chains in ICA was compared to the ICA titer, age of onset of IDD and HLA-DR phenotype of the patient. No statistical correlation could be detected at a P value less than 0.05. Our findings more likely exclude the occurrence of a single aberrant lymphocyte clone secreting ICA that may have arisen by somatic mutation in individual patients. Rather, these results are consistent with the hypothesis that ICA arise by polyclonal B-lymphocyte activation as a result of a defect of immune regulation. Since human antibodies to protein antigens are found predominantly in the IgG1 subclass, our findings support the belief that the autoantigen involved in the stimulation of ICA formation is comprised, at least in part, of protein.

Pneumococcal polysaccharide immunization in patients with active nephrotic syndrome

We have studied the IgG and IgM antibody responses to pneumococcal polysaccharides types 3 and 19 in eleven patients with active nephrotic syndrome and fifteen normal adult controls. Immunization in both patients with nephrotic syndrome and normal subjects resulted in significant increases in serum IgM antibody to types 3 and 19 pneumococcal polysaccharides. While controls also had a significant rise in IgG antibody to both types 3 and 19, patients with nephrotic syndrome had an increase in IgG antibody only to type 3. Also, after immunization, geometric mean titers of IgG antibodies to both types 3 and 19 were lower in patients with active nephrotic syndrome than in normal subjects (p less than 0.001). In patients with nephrotic syndrome, a significant correlation was found between serum albumin level and type 3 (p less than 0.01) and type 19 (p less than 0.05) antipneumococcal IgG antibody concentration. Furthermore, antipneumococcal IgG antibody was found in the urine of nephrotic patients, while no IgM antibody was excreted in the urine of nephrotic and adult controls. Our data demonstrate that patients with active nephrotic syndrome are able to mount a normal IgM immune response to pneumococcal polysaccharide antigens. The low IgG antibody levels are likely due to increased urinary losses and/or to a partial inability of these patients to produce IgG antibodies. Moreover, since protection may depend on antipneumococcal IgG antibody, these data raise questions as to the benefits of pneumococcal vaccination in patients with active nephrotic syndrome.

Evolution of the subclass of IgG antibody to type 3 pneumococcal polysaccharide during childhood

Human antibodies to bacterial polysaccharides consist primarily of IgG and are largely restricted to the IgG2 subclass in adults. We examined the ontogeny of the IgG subclass response to pneumococcal polysaccharide type 3 to determine if the poor response of infants to immunization with polysaccharide antigens is due to a diminished capacity to form this subclass of antibodies. Sera from 33 patients aged 2 months to 25 years who had previously been shown to respond to polyvalent pneumococcal polysaccharide vaccine by producing IgG antibodies, were assayed for pneumococcal type 3 specific antibodies of the IgG1, IgG2, IgG3, or IgG4 subclass. IgG1 antibodies to pneumococcal polysaccharide type 3 were uniformly low in all age groups. In contrast, IgG2 antibody activity was lowest in children less than the age of 2 years (170 +/- 20 ng/ml), but rose progressively in the age group 2-5 years (210 +/- 40 ng/ml), 5-10 years (330 +/- 30 ng/ml), and over the age of 10 (390 +/- 30 ng/ml) (differences significant at P less than 0.0005 by ANOVA). Thus, even in infants, pneumococcal polysaccharide responses are confined largely to the IgG2 subclass. Our findings are consistent with the hypothesis that purified bacterial capsular polysaccharide antigens preferentially activate IgG2-committed B cell clones at all ages.

T lymphocyte depletion of human peripheral blood and bone marrow using monoclonal antibodies and magnetic microspheres

It has previously been demonstrated that graft-versus-host disease can be overcome in patients receiving HLA-mismatched bone marrow transplants by prior in vitro depletion of T lymphocytes from the marrow. In this report we describe the use of monoclonal antibodies and magnetic microspheres for the depletion of T cells from peripheral blood and bone marrow. The target cells are sensitized with antibodies directed against the CD2, CD3, CD4 and/or CD8 cell surface antigens, captured by magnetic beads coated with sheep anti-mouse IgG antibody and collected by placing the cell suspension in a magnetic field. This simple, rapid procedure results in the efficient removal of T cells from peripheral blood and from bone marrow without affecting the colony-forming potential of normal hematopoietic stem cells. The procedure is capable of being scaled up for the treatment of larger volumes of marrow that are required for clinical transplantation.

Chromosomal localization of human ornithine aminotransferase gene sequences to 10q26 and Xp11.2

Gyrate atrophy is a hereditary chorioretinal degeneration associated with a deficiency of ornithine aminotransferase (OAT). By means of a complementary DNA clone encoding human OAT, the OAT gene sequences were mapped by somatic cell hybrids and in situ hybridization to human chromosome regions 10q26 and Xp11.2. A review of 80 biochemically confirmed cases of gyrate atrophy confirmed the autosomal recessive inheritance of this disease and supported the presence of a functional OAT gene on chromosome 10. Interestingly, the X chromosome OAT gene sequences (Xp11.2) map to the same region as L1.28 (Xp11.0-p11.3), a marker closely linked to X-linked recessive retinitis pigmentosa.

Retinal photoreceptor neurons and pinealocytes accumulate mRNA for interphotoreceptor retinoid-binding protein (IRBP)

We have utilized cDNA probes and in situ hybridization techniques to define the subcellular localization of interphotoreceptor retinoid-binding protein (IRBP) mRNA in bovine and monkey retinas. Results suggest that the mRNA is mainly localized in rod photoreceptor neurons within the outer nuclear layer of the retina. IRBP mRNA is also abundant in cells of the pineal gland, strengthening the analogy between rod photoreceptor cells and pinealocytes.

Association of class II human histocompatibility leukocyte antigens with rheumatic fever

The association of class I and II HLA antigens with rheumatic fever and its manifestations was examined in 72 patients, including 48 blacks and 24 Caucasians. No significant association was found between class I antigens and rheumatic fever. In contrast, HLA-DR2 and HLA-DR4 phenotypes were encountered in a significantly higher frequency in black and Caucasian patients with rheumatic fever, respectively, compared with the control populations (P less than 0.005). The most significant association (P less than 0.005) of these DR antigens with a major manifestation of rheumatic fever was found for mitral insufficiency. In addition, a significant association was encountered between persistent elevation of antibody to the group A streptococcal carbohydrate and HLA-DR4 in Caucasian patients (P less than 0.04) or HLA-DR2 in the black patients (P less than 0.001). The frequency of HLA-DR2/4 heterozygotes among patients with rheumatic fever did not differ significantly from controls. These findings support the concept of a genetically determined susceptibility to rheumatic fever and, particularly, to rheumatic heart disease. The association of the clinical manifestations of rheumatic fever and the immune hyperresponsiveness to a streptococcal antigen could be ascribed to a disease-associated immune-response gene which is in linkage disequilibrium with the DR2 and DR4 alleles of HLA-DR locus on chromosome six.

IgG2 subclass restriction of antibody to pneumococcal polysaccharides

Studies in experimental animals suggest that antibody responses to certain polysaccharide antigens may be restricted in IgG subclass distribution. To determine if human antibodies to pneumococcal polysaccharides are similarly restricted we measured the IgG subclass specific response to immunization with purified polyvalent pneumococcal polysaccharide vaccine. For the type 3 pneumococcal antigen, the geometric mean titre of IgG2 antibody was significantly greater than that of IgG1, IgG3 or IgG4, in both pre-immunization and post-immunization sera. A significant rise in mean titre, comparing pre- to post-immunization sera was observed only for IgG2 antibody. Similar predominance of IgG2 antibody was found for pneumococcal polysaccharides types 6, 18, 19 and 23. In contrast, antibody to the protein antigen tetanus toxoid was exclusively of the IgG1 subclass. Patients with IgA/IgG2 deficiency demonstrated a normal IgG response to tetanus, a normal IgM response to pneumococcal polysaccharides, but no IgG antibody to pneumococcal antigens. IgG2 subclass restriction of antibody to pneumococcal polysaccharides suggest that these antigens may elicit an immune response analogous to the murine type 2 T-cell independent immunogens which show IgG subclass restriction and the requirement of a mature B cell subset defined by the Lyb5+ alloantiserum. Our findings support the possibility of subclass-specific inducing or regulating mechanisms for human responses to carbohydrate or polysaccharide antigens.

cDNA clones encoding bovine interphotoreceptor retinoid binding protein

We have isolated a cDNA clone (lambda IRBP-1) for bovine interphotoreceptor retinoid-binding protein (IRBP) by immunological screening of a bovine retinal lambda gt11 cDNA expression library. This clone contained a cDNA insert 325 bp in length. A 250 bp fragment of this cDNA was used to screen a bovine retina lambda gt10 cDNA library, resulting in the isolation of two larger cDNA clones containing inserts of 2.5 kb (lambda IRBP-2) and 1.5 kb (lambda IRBP-3). Restriction endonuclease mapping revealed all three clones to have an EcoR I restriction site. The 250 bp fragment of lambda IRBP-1 and the 2000 bp fragment of lambda IRBP-2 both hybridized to a single bovine retinal mRNA species approximately 8 kb in length; there was no hybridization with either chicken lens or liver RNA. The amino acid sequence of a tryptic peptide from authentic IRBP has been obtained. The deduced amino acid sequence from the cDNA nucleotide sequence is the same as this authentic peptide. This definitively establishes the identity of the cDNA clones as encoding bovine IRBP.

The location of cardiac vagal preganglionic neurones in the brain stem of the dogfish Scyliorhinus canicula

The locations, within the brain stem, of vagal efferent preganglionic neurones with axons in the two pairs of cardiac vagal rami of the dogfish have been defined by the retrograde intra-axonal transport of horseradish peroxidase (HRP). HRP was applied to the cardiac rami in one of two ways: either as crystals placed on the cut central end of the nerve or as a dried concentrated solution administered into the nerve on the tip of a fine pin. No difference was observed in the number of labelled cell bodies identified using either method. Labelled branchial cardiac vagal motoneurones were found ipsilaterally in the medial division of the vagal motor column, in the lateral division of the vagal motor column, and scattered between these two locations. In contrast, visceral cardiac vagal motoneurones were confined to the ipsilateral medial division of the vagal motor column. We suggest that the dual location of cell bodies supplying axons to the branchial cardiac branch of the vagus may represent a separation of function with respect to the two types of activity conducted by this nerve. Cardiac efferent fibres are confined in their exit from the brain to a middle group of vagal rootlets. This corresponds to the topographical representation of cardiac efferent somata within the extent of the vagal motor column.

Spontaneous efferent activity in branches of the vagus nerve controlling heart rate and ventilation in the dogfish

Efferent activity was recorded from cranial nerves in the decerebrate dogfish (Scyliorhinus canicula) before and after injection of paralysing drugs. The recordings were made from the mandibular (Vth) and glossopharyngeal (IXth) nerves and the branchial (respiratory) and cardiac branches of the vagus (Xth) nerve. All the respiratory branches (Vth, IXth and Xth) and both cardiac branches fired rhythmic bursts of activity, synchronous with ventilation, which continued (at a higher rate) following paralysis, indicating that they originated in the CNS rather than arising reflexly from stimulation of pharyngeal mechanoreceptors. A burst of activity in the Vth nerve was followed by a burst in the IXth then, after a 30-ms delay, simultaneous bursts in the three respiratory branches of the Xth. The bursts in the branchial cardiac branches had a fixed phase relationship with activity in the respiratory branches, the onset of each burst preceding that in the immediately adjacent branch (branchial III), whereas the bursts in the visceral cardiac branches had a variable phase relationship with all other branches. The branchial cardiac branches alone contained units which fired sporadically between the bursts and increased their rate of firing during hypoxia. Both the bursting and non-bursting units responded to mechanical stimulation of the gill area. Separate oscillatory inputs driving the Vth, IXth and Xth respiratory motoneurones and an excitatory input to the bursting cardiac vagal motoneurones from expiratory motoneurones or the respiratory rhythm generator are implied by these relationships. The sporadically firing units in the branchial cardiac nerves clearly receive non-oscillatory inputs.

The characteristics of cardiac vagal preganglionic motoneurones in the dogfish

Preganglionic vagal motoneurones supplying the heart of the dogfish have been located in the medulla by antidromic stimulation of the central cut end of the branchial cardiac branch of the vagus. They supplied axons with conduction velocities between 4.75 and 16.3 m s-1, which is similar to mammalian B fibres. Motoneurones were found in two locations: the rostromedial (N = 5) and lateral (N = 12) divisions of the vagal motor column. Their measured depths and rostrocaudal distributions with respect to obex corresponded with the location of branchial cardiac motoneurones determined by horseradish peroxidase (HRP) histochemistry. All the neurones located in the rostromedial division of the vagal motor column were spontaneously rhythmically active. Their activity contributed to the rhythmic, respiratory-related bursts in peripheral recordings of efferent activity from the branchial cardiac vagus. They could be induced to fire in a prolonged burst by mechanical stimulation of the gill arches. The neurones located lateral to the rostromedial division of the vagal motor column could be divided into three categories: (1) spontaneously, continuously active cells which could be induced to fire more frequently by mechanoreceptor stimulation, (2) silent cells which could be induced to fire by mechanoreceptor stimulation, (3) silent cells which did not respond to mechanoreceptor stimulation. It is concluded, from the response of the medial and two categories of lateral cells to mechanoreceptor stimulation (which results in a transient bradycardia), that branchial cardiac motoneurones from both these central locations exert a chronotropic influence on the heart.

The location of cardiac vagal preganglionic neurones in the brain stem of the dogfish Scyliorhinus canicula

The locations, within the brain stem, of vagal efferent preganglionic neurones with axons in the two pairs of cardiac vagal rami of the dogfish have been defined by the retrograde intra-axonal transport of horseradish peroxidase (HRP). HRP was applied to the cardiac rami in one of two ways: either as crystals placed on the cut central end of the nerve or as a dried concentrated solution administered into the nerve on the tip of a fine pin. No difference was observed in the number of labelled cell bodies identified using either method. Labelled branchial cardiac vagal motoneurones were found ipsilaterally in the medial division of the vagal motor column, in the lateral division of the vagal motor column, and scattered between these two locations. In contrast, visceral cardiac vagal motoneurones were confined to the ipsilateral medial division of the vagal motor column. We suggest that the dual location of cell bodies supplying axons to the branchial cardiac branch of the vagus may represent a separation of function with respect to the two types of activity conducted by this nerve. Cardiac efferent fibres are confined in their exit from the brain to a middle group of vagal rootlets. This corresponds to the topographical representation of cardiac efferent somata within the extent of the vagal motor column.

Evidence of a respiratory role for the hypoxic bradycardia in the dogfish Scyliorhinus canicula L

Exposure to moderate hypoxia (P1, O2 50 mmHg) at 15 degrees C caused a bradycardia, with fH falling to approximately 50% of the normoxic level. Injection of atropine abolished the hypoxic bradycardia. Ventilation rate did not change during hypoxia. Atropinization caused significant reductions in the mean hypoxic levels of Pa, O2, Pv, O2 and Cv, O2. Calculated diffusive conductance for oxygen (DO2) was reduced by 28% following abolition of the hypoxic bradycardia, despite an assumption that cardiac output was unchanged. Factors, other than relative flow rates of water and blood, are clearly implicated in determining the effectiveness of gas exchange over the counter-current of blood and water at the gills of the dogfish.

Human immune responses to polysaccharide antigens: an analysis of bacterial polysaccharide vaccines in infants

Mechanisms of human immunity to polysaccharide encapsulated bacteria and the development and testing of the currently available purified polysaccharide bacterial vaccines are reviewed. These vaccines appear to be poorly immunogenic in infants under the age of two years--those at greatest risk for infection. In an effort to understand the poor responses of infants, the human immune response to polysaccharide antigens was characterized in more detail. Using pneumococcal polysaccharide type 3 as an example, it appears that human polysaccharide antibody responses are analogous to the type 2 T cell independent responses defined in the murine system. These studies suggest that the deficient polysaccharide response of human infants is due to a deficiency in maturation of distinct B lymphocyte subpopulations, as well as imbalanced T regulatory influences. The development of vaccines containing the purified capsular polysaccharides of S. pneumoniae, H.influenzae, and N. meningitidis during the past decade offered promise for the prevention of the major causes of bacterial sepsis and meningitis during childhood. The fulfillment of that promise was thwarted by the unrecognized complexities of human antibody responses to polysaccharide antigens. Continued vigorous research in this area has led us to a better understanding of the cellular requirements and immunoregulation of human polysaccharide antibody responses and has given us a clear direction for the pursuit of an effective means for immunization of infants.

IgG and IgM pneumococcal polysaccharide antibody responses in infants

The ontogeny of human antibody responses to pneumococcal polysaccharide antigens was studied by determining whether the age at immunization affects the level and/or immunoglobulin isotype of antibody produced. Twenty-nine healthy infants between 2 and 18 months of age and 13 normal adults were studied. Responses were found to vary markedly with the age at the time of immunization and with the pneumococcal serotype tested. Three general patterns of isotype-specific antibody response were observed in the infants: a high response in IgG antibody occurred as early as 2 months of age following immunization with type 3 pneumococcal polysaccharide; little or no response was noted in either IgG or IgM antibody with types 6, 18, and 19; and intermediate responses with IgM antibody increases greater than IgG increases were found for type 23. These data suggest that different factors control the immunologic response of infants to various pneumococcal polysaccharide serotypes following immunization at various ages.

Characterization of the acquired immune deficiency syndrome at the cellular and molecular level

The acquired immunodeficiency syndrome (AIDS) is a new disease characterized by severe dysfunction of both the T cell and B cell systems, occurring in previously healthy individuals. Affected individuals may have recurrent and chronic opportunistic infections and/or Kaposi's sarcoma or other malignancy. Analysis of the cellular and subcellular components of immunity demonstrates a profound depression in the number and function of helper/inducer T cells bearing the OKT4 (Leu 3) differentiation antigen and a concomitant defect in the synthesis of the immuno-enhancing soluble growth factor, interleukin 2 (IL-2). Hypotheses to explain the etiology of the immunological dysfunction and implications for future therapy of AIDS are discussed.

Prevalence of T-lymphocyte abnormalities in infants with congenital heart disease

Thirty-two infants younger than 6 months with catheterization-proved congenital heart disease were prospectively examined for T-lymphocyte immunodeficiency (compared with adult and normal newborn controls). Cardiac lesions were separated into two groups: (1) "high-risk" lesions previously associated with T-cell abnormalities in DiGeorge's syndrome, and (2) the remaining "low-risk" lesions. Cardiac patients as a whole did not have significant abnormalities in T-cell rosette (TCR) percentages (mean +/- SE, 50.0% +/- 22%) or response to phytohemagglutinin (PHA) (72,243 +/- 38,388 counts per minute). However, a greater percentage of patients with high-risk cardiac lesions had abnormal TCR and PHA results than either the control or low-risk group, due to the inclusion of three infants with DiGeorge's syndrome. These findings suggest that newborn infants without evidence of DiGeorge's syndrome have normal T-lymphocyte function. Infants with high-risk cardiac lesions deserve a careful immunologic evaluation to avoid significant morbidity and mortality.