Geographical variation in Ascaris lumbricoides fecundity and its implications for helminth control

The observation by microscopy of nematode eggs in human faeces is used to diagnose a helminthic infection, while the concentration of those eggs is used to estimate the number of worms in the host. Within a community, the prevalence of infection and the mean egg count provide useful information about the extent of a public health problem, and are being used to guide the growing efforts to control disease caused by helminths. Here, Andrew Hall and Celia Holland examine data on the relationship between the worm burdens of Ascaris lumbricoides and the concentration of eggs in faeces, and discuss the implications of the variation found for using such data to plan helminth control programmes.

Parasite community similarity between four Irish lakes

A total of 140 trout were examined from four lakes in north west Ireland, Loughs Craghy, Waskel, Meela and Owennamarve. Eleven species of metazoan parasite were recorded, ten of which were of freshwater origin and Anisakissp. was the only marine species. No acanthocephalan species were found. Diphyllobothrium ditremum, D. dendriticum and Anisakissp. were the only allogenic species. Lough Owennamarve had the largest component community with nine species recorded. Lough Meela, the only brackish water lake had the smallest component community with six species recorded. Lough Waskel and Craghy had intermediate component community values. Lough Meela showed the lowest levels of similarity to any of the other lakes. Values for the Shannon-Wiener diversity index were highest for Lough Owennamarve and lowest for Lough Meela and intermediate for the other two lakes. Lough Meela had the highest values for the Simpson's dominance index and the Berger-Parker index. Lough Owennamarve had the highest Brillouin's index and Lough Meela had the lowest. The use of multiple regression techniques to control for the potentially confounding effect of geographical distance as a predictor of community similarity was discussed. No parasite species found could be considered as regionally and locally abundant and therefore described as a core species. The helminth community appears to have some degree of predictability, but chance colonization events are also important.

Decay of large underwater bubble oscillations

Pressure-time series from breathing-mode oscillation of large (centimeter scale or larger) underwater bubbles reveal much higher decay rates than can be explained using viscous, thermal, or radiative mechanisms which apply to microbubbles. It is shown that if one assumes energy transfer to shape oscillations (surface capillary waves) of large amplitude in subharmonic resonance with the breathing mode [M. S. Longuet-Higgins, J. Acoust. Soc. Am. 91, 1414 (1992)], then the shape oscillations can drive fluid motions outside the bubble capable of exciting turbulent instabilities. Application of an appropriate eddy viscosity from mixing-length theory to the viscous decay mechanism appears to offer a credible explanation for the observed large decay rates. An analysis is given to show that energy is transferred from the breathing mode to surface capillaries fast enough to make the proposed decay mechanism viable.

T-lymphocyte subsets in HIV-infected and high-risk HIV-uninfected adolescents: retention of naive T lymphocytes in HIV-infected adolescents. The Adolescent Medicine HIV/AIDS Research Network

BACKGROUND

The capacity of the immune system of adolescents to generate and repopulate naive and memory cell populations under conditions of normal homeostasis and human immunodeficiency virus (HIV) infection is largely unknown.

OBJECTIVE

To assess lymphocyte subsets in HIV-infected and high-risk HIV-negative adolescents.

DESIGN

The Reaching for Excellence in Adolescent Care and Health Project of the Adolescent Medicine HIV/AIDS Research Network recruits a cohort of HIV-infected and high-risk HIV-uninfected adolescents, aged 13 to 18 years 364 days, into a study of biomedical and behavioral features of HIV infection as seen in the context of full availability of primary care and HIV-related consultative services. Lymphocyte phenotypes were determined using standard 3-color flow cytometry.

SETTING

The Reaching for Excellence in Adolescent Care and Health Project is carried out at 16 clinical sites in 14 urban areas.

PARTICIPANTS

T-lymphocyte subsets are reported in 192 HIV-positive and 78 HIV-negative youths.

RESULTS

For HIV-positive subjects, the total CD4+ cell count and the percentage of CD4+ cells are decreased when compared with those of the HIV-negative controls (P<.001). The reduction in total CD4+ cells reflects a loss of naive, and memory, CD4+ cells compared with HIV-negative youths. Human immunodeficiency virus-infected adolescents, many of whom have been infected recently (ie, those with CD4+ cell counts > or =0.500 x 10(9)/L [500/microL]), have a significant increase in naive CD8+ cells compared with HIV-negative youths (P<.01). There also is a significant increase in memory CD8+ cells at all strata of total CD4+ cells compared with HIV-negative youths (P<.01). The increase in naive CD8+ cells in those subjects with CD4+ cell counts of 0.500 x 10(9)/L or greater is a unique finding in this cohort.

CONCLUSIONS

This study demonstrates high levels of naive CD8+ cells in response to HIV infection in adolescents with CD4+ cell counts of 0.500 X 10(9)/L or greater. The presence of high levels of naive CD8+ cells suggests functioning thymic tissue in some adolescents infected with HIV. Furthermore, the normal level of naive CD4+ cells in adolescents with CD4+ levels of 0.500 x 10(9)/L or greater provides additional support for the concept of a more robust immune system in HIV-infected adolescents compared with HIV-infected adults. These observations suggest that the immune system of HIV-infected adolescents may be capable of better responses to neoantigens and cytotoxic T-lymphocyte responses to HIV than the immune system of infected children or adults. Human immunodeficiency virus-infected adolescents may have an immune system that is capable of reconstitution following highly active antiretroviral therapy.

Proinflammatory cytokine expression of IL-1beta and TNF-alpha by human osteoblast-like MG-63 cells upon exposure to silicon nitride in vitro

This study was designed to determine the effect of Si(3)N(4) disks and particulates on human osteoblast-like MG-63 cells in vitro. The MG-63 (10(5)/mL) cells were plated onto 24-well polystyrene plates fitted with either sintered reaction-bonded (SRBSN) or reaction-bonded (RBSN) 15-mm disks. Controls consisted of wells without Si(3)N(4) disks. Cells propagated at 37 degrees C, 5% CO(2) for 48 h on Si(3)N(4) disks and control polystyrene surfaces exhibited similar proliferative capacities (7000 and 4000 cpm/10(5) cells, respectively, p > 0.05). Cells incubated with 1, 10, or 100 microgram/ml of Si(3)N(4) particles (<1.00 to 5.00 micrometer) for 24 h did not exhibit a decrease in DNA synthetic activity: 12 +/- 1.3 x 10(4), 10.5 +/- 1.5 x 10(4), and 11.0 +/- 1.7 x 10(4) cpm, respectively, compared to 11.6 +/- 2.6 x 10(4) cpm/10(5) for the control cells, as indicated by (3)H-thymidine uptake. Cells propagated on RBSN displayed increased expression of cytokines IL-1beta and TNF-alpha compared to the control cells, as shown by reverse transcriptase-polymerase chain reaction (RT-PCR). In contrast, cells propagated on SRBSN surfaces expressed the same level of IL-1beta and TNF-alpha as that of control cells. Incubation of MG-63 cells with 1-10 microgram/mL of particles did not increase IL-1beta expression. However, at 100 microgram/mL, TNF-alpha expression was greater than that of the control cells. Silicon nitride, evaluated here as disks or as particulates (1-10 microgram/mL), is biocompatible and does not hinder the proliferation or induce proinflammatory cytokine expression of human osteoblast-like MG-63 cells in vitro.

Peripheral blood mononuclear cell markers in antiretroviral therapy-naive HIV-infected and high risk seronegative adolescents. Adolescent Medicine HIV/AIDS Research Network

OBJECTIVE

To examine potential hematologic and immunologic markers for healthy adolescents and for adolescents infected with HIV.

DESIGN

The REACH Project (Reaching for Excellence in Adolescent Care and Health) of the Adolescent Medicine HIV/AIDS Research Network (AMHARN) recruits HIV-infected and high-risk HIV-uninfected adolescents, aged at least 13 but less than 19 years. The study evaluates biomedical and behavioral features of HIV infection as observed while under medical care for HIV infection and adolescent health.

METHODS

Blood samples were collected from HIV-infected and HIV-uninfected subjects at 16 clinical sites. Cell phenotypes were determined using standard single, dual or three-color flow cytometry.

RESULTS

This report includes data at enrollment for 94 HIV-positive adolescents who had never received antiretroviral therapy (ART) (mean age, 17.4 +/- 1.0 years for males and 16.5 +/- 1.3 years for females) and 149 HIV-negative adolescents (mean age, 16.7 +/- 1.2 years for males and 16.6 +/- 1.2 years for females); this is the antiretroviral therapy-naive subset drawn from 294 HIV-positive and 149 HIV-negative adolescents enrolled in the REACH Cohort. The total leukocyte count was significantly reduced in the HIV-positive females in comparison with the HIV-negative females (P < 0.001). There was a reduction in natural killer cells (P < 0.05) in HIV-positive females (mean, 140.6 +/- 104.2 x 10(6) cells/l) in comparison with HIV-negative females (184.3 +/- 142.5 x 10(6) cells/l), whereas no differences were found between the two groups of males. The reduction in the total CD4 cell count in HIV-positive males and females in comparison with the HIV-negative subjects was the consequence of a decrease in both the naive CD4 and memory CD4 components. There was a striking increase in the mean number of CD8 memory cells in HIV-positive compared with HIV-negative adolescents, and a corresponding increase in the percentage of these cells. In contrast, naive CD8 cells were present in increased numbers but their percentage was decreased.

CONCLUSIONS

These studies of adolescents provide normative data for high-risk healthy adolescents as well as baseline immunologic data for a cohort of ART-naive HIV-positive adolescents. This comparison suggests that this untreated, recently infected group had relatively intact immunologic parameters.

Acute effects of nebulised epoprostenol in pulmonary hypertension due to systemic sclerosis

Pulmonary hypertension often has a lethal outcome in systemic sclerosis and the treatment is challenging. Epoprostenol is a potent pulmonary vasodilator and its efficacy has been demonstrated when delivered by the intravenous and aerosolized routes. We report the haemodynamic and functional benefits of epoprostenol administered by inhalation to a spontaneously breathing patient with partially reversible pulmonary hypertension due to systemic sclerosis. Aerosolized epoprostenol, equivalent to the maximum tolerated intravenous dose (31.2 micrograms), produced a 58% fall in pulmonary vascular resistance, increased the cardiac output by 42% and improved functional performance by one MET (3.5 ml kg-1 min-1 of oxygen uptake) without any significant side-effects. Selective distribution of epoprostenol by the inhaled route may offer a new strategy for treatment of pulmonary hypertension.

Passive transfer of growth-inhibitory antibodies raised against yeast-expressed recombinant Plasmodium falciparum merozoite surface protein-1(19)

Purified rabbit immunoglobulin raised against yeast-expressed recombinant FVO or 3D7 Plasmodium falciparum merozoite surface protein-1 (MSP-1) 19k-D C terminal fragment (MSP-1(19)) was transfused into malaria-naive Aotus nancymai monkeys that were immediately challenged with FVO asexual stage malaria parasites. Control monkeys received rabbit immunoglobulin raised against the sexual stage antigen Pfs25 or Aotus hyperimmune serum obtained from monkeys immunized by P. falciparum infection and drug cure. Passive transfer of rabbit anti-MSP-1(19) failed to protect against homologous or heterologous challenge and, when compared with negative controls, there were no differences in prepatent periods or time to treatment. Interestingly, rabbit anti-MSP-1(19), but not anti-Pfs25, immunoglobulin, and immune monkey serum prevented the development of antibodies directed against MSP-1(19) fragment by infected monkeys, indicating that the antibodies were reactive with native MSP-1(19) antigen in vivo. The prepatent period and time to treatment was greatly delayed in the two monkeys that received Aotus immune serum, both of which developed a chronic intermittent low level infection. In vitro parasite growth inhibition assays (GIAs) confirmed the presence of inhibitory activity (40% maximum inhibition) in concentrated anti-MSP-1(19) immunoglobulin (4.8 mg/ml), but the peak concentrations we achieved in vivo (1 mg/ml) were not inhibitory in vitro. Subinhibitory levels of anti-MSP-1(19) antibodies achieved by passive transfer were not protective against P. falciparum challenge.

Paving the road to maximum productivity

"Job security" is an oxymoron in today's environment of downsizing, mergers, and acquisitions. Workers find themselves living by new rules in the workplace that they may not understand. How do we cope? It is the leader's charge to take advantage of this chaos and create conditions under which his or her people can understand the need for change and come together with a shared purpose to effect that change. The clinical laboratory at Arkansas Children's Hospital has taken advantage of this chaos to down-size and to redesign how the work gets done to pave the road to maximum productivity. After initial hourly cutbacks, the workers accepted the cold, hard fact that they would never get their old world back. They set goals to proactively shape their new world through reorganizing, flexing staff with workload, creating a rapid response laboratory, exploiting information technology, and outsourcing. Today the laboratory is a lean, productive machine that accepts change as a way of life. We have learned to adapt, trust, and support each other as we have journeyed together over the rough roads. We are looking forward to paving a new fork in the road to the future.

Long-term efficacy and immune responses following immunization with the RTS,S malaria vaccine

The malaria sporozoite vaccine candidate RTS,S, formulated with an oil-in-water emulsion plus the immunostimulants monophosphoryl lipid A and the saponin derivative QS21 (vaccine 3), recently showed superior efficacy over two other experimental formulations. Immunized volunteers were followed to determine the duration of protective immune responses. Antibody levels decreased to between one-third and one-half of peak values 6 months after the last dose of vaccine. T cell proliferation and interferon-gamma production in vitro were observed in response to RTS,S or hepatitis B surface antigen. Seven previously protected volunteers received sporozoite challenge, and 2 remained protected (1/1 for vaccine 1, 0/1 for vaccine 2, and 1/5 for vaccine 3). The prepatent period was 10.8 days for the control group and 13.2 days for the vaccinees (P < .01). Immune responses did not correlate with protection. Further optimization in vaccine composition and/or immunization schedule will be required to induce longer-lasting protective immunity.

Patients' recollections of critical care

Warm, caring, competent critical care nurses who communicate respect for patients' dignity and individuality alleviate fear and stress of a critical care unit stay. Patients perceive these nurses as professionals who deliver quality care. When cared for by critical care nurses with these characteristics, patients' satisfaction with care is heightened. This article provides an insight to patients' responses concerning their care in a critical care unit.

Paroxetine and pindolol: a randomized trial of serotonergic autoreceptor blockade in the reduction of antidepressant latency

A double-blind, randomized, placebo-controlled, parallel group study was performed in 80 adult outpatients meeting ICD-10 criteria for major depression and with a Montgomery-Asberg Depression Rating Scale (MADRS) score of at least 18 at baseline. All patients received paroxetine (20 mg once a day) plus either pindolol (2.5 mg three times a day) or matching placebo for 6 weeks. Analysis of the day 14 MADRS scores on an intent-to-treat basis revealed a treatment-by-centre interaction, with a significant effect of pindolol being demonstrable at only one centre. At this centre, 25% of the paroxetine plus pindolol group and 0% of the paroxetine plus placebo group showed a decrease of at least 50% from baseline MADRS by day 4 (p < 0.05). At day 14, the proportions were 73% and 7%, respectively (p < 0.001). Analysis of covariance on a "perprotocol" population demonstrated a significant accelerator effect of pindolol at days 4 and 7 in the absence of a treatment-by-centre interaction, but a centre effect was apparent at later time-points. The results suggest that the latency of antidepressant action can be reduced with pindolol augmentation. A large multicentre study is in progress to investigate this effect further.

Metazoan parasite community structure in brown trout from two lakes in western Ireland

A total of 549 brown trout were caught from two lakes, Lough Feeagh and Bunaveela Lake, in the Burrishoole system, Co. Mayo, Ireland. Seven species of metazoan parasite were detected but only four species occurred in > or = 10% of the sample. The parasite community of the trout was dominated by a single species, Pomphorhynchus laevis, with a prevalence if 58%. Only one allogenic helminth species was recorded from the trout, Diphyllobothrium ditremum, with the community mainly comprising autogenic species. Few differences were found between the two lakes, although the larger lake, Lough Feeagh, did contain some trout which harboured more parasite species and had, on average, fish with higher numbers of individual parasites. Measures of species richness and diversity were very low, indicating an impoverished helminth community with little potential for interspecific interactions. Host age was found to significantly influence these indices of infracommunity structure.

Population biology of Pomphorhynchus laevis in brown trout from two lakes in the west of Ireland

Since Ireland is the only country in which Pomphorhynchus laevis (Acanthocephala) uses brown trout (Salmo trutta) as its preferred definitive host, the population biology of the parasite in this host was investigated thus enabling a comparison to be made with data collected on P. laevis from other hosts, particularly the cyprinids, chub and barbel. Over a period of 12 months, 549 brown trout were caught from two lakes, Lough Feeagh and Bunaveela Lake, in the Burrishoole River system, Co. Mayo, Ireland. The parasite component community was dominated by a single species, P. laevis. Fifty eight percent of the trout sample were infected with the acanthocephalan and the mean abundance (+/- SD) was 3.1 +/- 5.1 The relationships between the prevalence and abundance of P. laevis and season and site of host capture and host age and sex were explored. As single factors one of these parameters emerged as significant contributions to changes in parasite abundance although some interaction terms proved to the significant. A random sample of over 700 P. laevis parasites were subjected to further investigation and their size, position in the intestine and maturity status are described. Parasites attained an average weight of 7 mg and occupied the posteriad positions within the fish intestine (77%). Parasites from this sample of Irish brown trout attained a similar average size to those found in chub and barbel from England. 42.3% of the total parasites examined contained ovarian balls only and 17% contained fully mature acanthors. Therefore only a moderate proportion of female worms contained mature acanthors in these trout whereas the majority of worms recovered from a sample of chub were gravid. Utilizing a logistic regression model, parasite size, season, and site of host capture emerged as particularly significant factors which contribute to whether a parasite contains mature eggs.

The effects of azidothymidine therapy on pseudocholinesterase concentrations in asymptomatic HIV-positive patients

The purpose of this study was to determine if a correlation exists between long-term azidothymidine (AZT) therapy and low pseudocholinesterase concentrations in patients who are infected with the human immunodeficiency virus (HIV). A pilot study was conducted of 10 patients infected with HIV, 5 of whom were receiving AZT. Laboratory tests, including complete blood count (CBC), liver function tests, helper/inducer T lymphocyte numbers (CD4), serum dibucaine numbers, and serum pseudocholinesterase concentrations were examined. Control and study subjects both exhibited normal dibucaine numbers, but the pseudocholinesterase concentrations were significantly lower in the group that was not receiving AZT relative to the AZT treatment group. However, only two patients, neither of whom were receiving AZT, demonstrated low or borderline low pseudocholinesterase concentrations according to laboratory criteria. It is possible that pseudocholinesterase synthesis is significantly inhibited by the HIV disease process and that treatment with AZT partly reverses the inhibition. Associated variables contributing to low pseudocholinesterase concentrations in the HIV-positive patient are explored.

Correlation between cellular rejection of cardiac allografts and quantitative changes among T-cell subsets identified by V beta epitope expression

BACKGROUND

Cellular rejection of an allograft is mediated in part by peripheral blood T cells. We tested the hypothesis that quantitative changes in T-cell subsets can be detected in the peripheral blood and that these changes correlate with rejection.

METHODS AND RESULTS

T-cell subset analysis was performed by flow cytometry using monoclonal antibodies recognizing six isotypic epitopes of the T-cell receptor beta-chain variable (V) region. These analyses were done at 7-day (mean) time intervals. Fluctuations within a given subset were determined by dividing the number of positive cells observed by the number of positive cells found on the previous analysis. For healthy volunteers observed over a period of 30 days, 119 of 120 subset ratios (99.2%) fell between 0.5 and 2.0. For patients, 57 of 240 subset ratios (23.8%) fell outside of this range (P < .004, chi 2). The occurrence of the abnormal ratios coincided more closely with cellular rejection (mean +/- SD, 7.7 +/- 6.2 days from a positive biopsy; median, 5 days; range, 0 to 28 days) than did the occurrence of normal subset ratios (mean +/- SD, 14.4 +/- 10.9 days from a positive biopsy; median, 11 days; range, 0 to 44 days; P < .005 by Mann-Whitney U test). Regression analysis confirmed a significant (P < .001, R = .91) temporal association between cellular rejection and abnormal subset fluctuations. No correlation was found between abnormal subset ratios and either vascular rejection or use of high-dose prednisone.

CONCLUSIONS

T-cell subset measurement may be a method of noninvasive monitoring of cellular rejection after transplantation and may provide insights into the physiology of graft rejection with the potential for the development of more specific immunosuppressive therapy.

Paternity by cardiac transplant recipients

To assess whether children fathered by cardiac transplant recipients are at high risk of teratogenicity, cardiac transplant centers listed with the International Society for Heart and Lung Transplantation were surveyed. Paternities after transplantation by heart (n = 35) and heart-lung (n = 1) allograft recipients have resulted in 42 pregnancies (children's age 3.3 +/- 0.3 years). The fathers' age at conception was < 45 years in 40 (95%) and > 45 years in 2 (5%). Most fathers (86%) were enjoying an active and healthy lifestyle at the time of conception; one (2%) was on dialysis and listed for kidney transplantation due to nephrotic syndrome, 1 (2%) had asthma, 4 (10%) had allograft coronary disease (1 died while waiting for second heart transplant when the child was 2 months old), and 2 (5%) were retransplanted after the pregnancies. Immunosuppressive regimens were reported for 37 paternities; drug protocols at the time of conception were as follows: 25 (60%) CsA/prednisone/AZA, 6 (14%) CsA/prednisone, 4 (10%) CsA/AZA, and 2 (5%) AZA/prednisone. Twenty-six (62%) had received treatment for rejection episodes before conception; seven (17%) had received treatment for rejections since conception. Of the 42 children fathered by these recipients, 3 (7%) were preterm, 1 (2%) had a cleft palate and lip that have subsequently been corrected, 1 (2%) died from interruption of umbilical cord circulation at 24 weeks, and 1 (2%) whose father had familial cardiomyopathy was born with a cardiomyopathy that improved with time. Although the numbers are small, the available data suggest that paternity by cardiac transplant recipients may be safe.

Plasmodium falciparum: further characterization of a functionally active region of the merozoite invasion ligand EBA-175

A 42 amino acid peptide, Pf EBA-175 (1062-1103), also called EBA-peptide 4 of the 175-kDa Plasmodium falciparum sialic acid binding protein, a putative merozoite invasion ligand, has been shown to be a target of parasite growth inhibitory antibodies. We expressed and purified a recombinant protein, NS1-Pf EBA-175 (946-1133) which included the 42 amino acid peptide, and compared antibodies induced by immunization with the protein to antibodies raised against the 42 amino acid peptide. Sera from rabbits immunized with the recombinant protein and the synthetic peptide immunoprecipitated authentic EBA-175, and had comparable ELISA titers against peptide Pf EBA-175 (1062-1103). However, IFAT titers against infected erythrocytes and growth inhibitory activity were substantially higher in sera from animals immunized with the 42 amino acid synthetic peptide. Epitope mapping of the 42 amino acid peptide identified a 19 amino acid peptide, Pf EBA-175 (1069-1087), which blocked the ability of antibodies against the 42 amino acid peptide to (1) immunoprecipitate EBA-175, (2) bind to the 42 amino acid peptide in an ELISA, and (3) recognize infected parasites in an IFAT. Sera from rabbits immunized with the 19 amino acid peptide conjugated to KLH had excellent parasite growth inhibitory activity (at 1:5 serum dilution, 49.9 +/- 7.4%, mean +/- SD of three separate assays), but the activity was lower in each of the three assays than that of sera from rabbits immunized with the 42 amino acid peptide (67.8 +/- 24.8%). These data indicate that the activity of antibodies raised against the linear 42 amino acid peptide, Pf EBA-175 (1062-1103) are primarily, if not exclusively, directed against 19 of the 42 amino acids, and identify this region of Pf EBA 175 as a target for vaccine development.

Do clinicians tell each other enough? An analysis of referral communications in two specialties

Referral letters and replies are an important vehicle for conveying information about patients and for creating and sustaining professional relationships. Studies of communication between hospital specialists and GPs, however, suggest that improvements could be made to the content of letters. In this study, which is part of a larger study of referral expectations, a sample of 39 letters to and from the ENT and Rheumatology departments at Sunderland Royal Infirmary was analysed to find out what objectives were being achieved through the correspondence between consultants and GPs. An analytical framework of letter content was derived from a review of 25 letters to and from each specialty and from a separate study of doctors' opinions of letter content conducted by two of the authors. Doctors recruited to the present study were involved in devising a weighted scoring system for letter content. Analysis showed that the letters accomplish the basic objective of transferring clinical and administrative information. They were less likely to contain items of a socio-psychological type. There was very little difference in the standardized letter scores between the two specialties. While the level of detail recorded in this sample may be adequate for straightforward referrals, there are indications that clinicians' letters are frequently not addressing nonclinical matters that can be a complicating factor in a proportion (perhaps a fifth) of referrals. This may be a possible topic for audit in multidisciplinary groups.

Increased frequency of alloantigen-reactive helper T lymphocytes is associated with human cardiac allograft rejection

Endomyocardial biopsy (EMB) is the standard method of monitoring heart transplant recipients for the development of allograft rejection. To date, noninvasive methods to detect cardiac allograft rejection have lacked adequate sensitivity and specificity for wide clinical application. In this study, limiting dilution analysis (LDA) was used to quantitate the number of donor alloantigen-reactive helper T lymphocytes (HTLs) in the peripheral blood of cardiac transplant recipients. Cadaveric donor splenocytes were cryopreserved, providing a source of donor alloantigenic stimulation for these assays. Peripheral blood mononuclear cells were harvested from cardiac transplant recipients before transplantation and at the time of EMB. LDA of donor-reactive HTLs was conducted simultaneously on all time points to minimize experimental variation, and these data were related to EMB scores. Frequencies of donor-reactive HTLs in pretransplant samples were highly variable, ranging from 1/1381 to < 1/200,000, and correlated poorly with the degree of HLA disparity. During episodes of moderate rejection, donor-specific HTL frequencies increased an average of 6 times their post-transplant baseline frequency. Additionally, 10-fold increases in HTL frequencies were seen preceding EMB-diagnosed rejection in several individuals. These data indicate that episodes of allograft rejection are associated with increases in the number of circulating donor-reactive HTL which are frequently detected before the development of histologically defined rejection. Thus, monitoring HTL frequencies may serve as a non-invasive method for detecting and predicting cardiac allograft rejection. Furthermore, this assay may provide a valuable means of assessing the in vivo efficacy of various immunosuppressive therapies.