Longitudinal CSF and MRI biomarkers improve the diagnosis of mild cognitive impairment

The diagnosis of Alzheimer's disease (AD) in patients with mild cognitive impairment (MCI) is limited because it is based on non-specific behavioral and neuroimaging findings. The lesions of Alzheimer's disease: amyloid beta (Abeta) deposits, tau pathology and cellular oxidative damage, affect the hippocampus in the earlier stages causing memory impairment. In a 2-year longitudinal study of MCI patients and normal controls, we examined the hypothesis that cerebrospinal fluid (CSF) markers for these pathological features improve the diagnostic accuracy over memory and magnetic resonance imaging (MRI)-hippocampal volume evaluations. Relative to control, MCI patients showed decreased memory and hippocampal volumes and elevated CSF levels of hyperphosphorylated tau and isoprostane. These two CSF measures consistently improved the diagnostic accuracy over the memory measures and the isoprostane measure incremented the accuracy of the hippocampal volume achieving overall diagnostic accuracies of about 90%. Among MCI patients, over 2 years, longitudinal hippocampal volume losses were closely associated with increasing hyperphosphorylated tau and decreasing amyloid beta-42 levels. These results demonstrate that CSF biomarkers for AD contribute to the characterization of MCI.

Relevance of postmortem radiology to the diagnosis of fatal cerebral gas embolism from compressed air diving

AIMS

To test the hypothesis that artefact caused by postmortem off-gassing is at least partly responsible for the presence of gas within the vascular system and tissues of the cadaver following death associated with compressed air diving.

METHODS

Controlled experiment sacrificing sheep after a period of simulated diving in a hyperbaric chamber and carrying out sequential postmortem computed tomography (CT) on the cadavers.

RESULTS

All the subject sheep developed significant quantities of gas in the vascular system within 24 hours, as demonstrated by CT and necropsy, while the control animals did not.

CONCLUSIONS

The presence of gas in the vascular system of human cadavers following diving associated fatalities is to be expected, and is not necessarily connected with gas embolism following pulmonary barotrauma, as has previously been claimed.

Transcutaneous oxygen measurements: implications for nursing

Transcutaneous oxygen measurement is a noninvasive diagnostic technique that records the partial pressure of oxygen at the skin surface. This measurement provides information regarding the supply and delivery of oxygen to the underlying microvascular circulation. It can be used for adults in wound evaluation, hyperbaric therapy, plastic surgery, amputation level determination, and peripheral vascular disease assessment, including the status of limb revascularization procedures. This article presents an overview of transcutaneous oxygen measurement and situations that influence measurement levels, including environmental, dermal, physiologic, and mechanical factors. Nursing considerations and indications for further research are also discussed.

Inhospital cardiac arrest: pre-event variables and nursing response

This retrospective study examined the medical records of 100 patients who experienced an in-hospital cardiopulmonary arrest. The purposes of this study were to identify pre-arrest physiologic changes that may have occurred in the patient and to determine whether physician notification time, physiologic variables, patient location, and the presence of an electrocardiogram (ECG) monitor before the arrest affected the resuscitation outcome. The results showed that assessment variances were present in most patients before the arrest and also were recognized by the nursing staff. Implications for practice include formation of quality improvement screening tools to assess the patient's pre-arrest status, development of competency tests that include scenarios involving changes in a patient's physiologic parameters, staff education, and evaluation of current nursing policies for obtaining vital signs and assessments.

Obstetric and newborn outcomes in a cohort of HIV-infected pregnant women: a report of the women and infants transmission study

OBJECTIVE

To determine obstetric and neonatal outcomes in a cohort of HIV-infected pregnant women and to assess whether HIV-related immunosuppression increases the risk of adverse outcomes of pregnancy.

METHODS

Between 1989 and 1994, interview, physical examination, laboratory, and medical record data were prospectively collected from HIV-infected pregnant women and on their newborns. Factors associated with adverse pregnancy outcome and HIV disease status were correlated with pregnancy outcome using logistic regression analysis.

RESULTS

634 women delivered after 24 weeks of gestation. Preterm birth, low birth weight, and small-for-gestational-age neonates occurred in 20.5%, 18.9%, and 24.0% of pregnancies, respectively. Factors associated with low birth weight were CD4 percentage <14%, history of adverse pregnancy outcome, pediatric HIV infection, bleeding during pregnancy, and Trichomonas infection. Preterm birth was associated with CD4 percentage <14%, a history of adverse pregnancy outcome, and bleeding during pregnancy. Being small for gestational age was associated with maternal hard drug use during pregnancy, Trichomonas infection, history of adverse pregnancy outcome, and hypertension.

CONCLUSIONS

Adverse pregnancy outcomes are common for HIV-infected women and are associated with low maternal CD4 percentage and pediatric HIV infection. Preterm birth, low birth weight, and small-for-gestational-age ranking, however, are also associated with previously recognized sociodemographic and obstetric factors that are not unique to HIV infection.

Serum vitamin A concentrations in a North American cohort of human immunodeficiency virus type 1-infected children. National Institute of Child Health and Human Development Intravenous Immunoglobulin Clinical Trial Study Group

BACKGROUND

Vitamin A deficiency is associated with increased risks of vertical transmission of HIV-1 (HIV) and of disease progression and mortality among HIV-infected adults. The objectives of the study were to describe serum vitamin A concentrations among HIV-infected children in the National Institute of Child Health and Human Development IVIG Clinical Trial, to examine changes in vitamin A concentrations and to investigate the relationships between vitamin A concentrations and morbidity and mortality.

METHODS

Blood was collected from children at baseline and at 3-month intervals throughout the study. Serum samples were stored at -70 degrees C at a central repository until retrieved for vitamin A assay. Samples were hexane-extracted and assayed by high performance liquid chromatography. The rate of change in vitamin A concentrations, calculated by fitting a linear regression model, was expressed as micrograms/dl/year.

RESULTS

The median vitamin A concentration at baseline (n = 207 children) was 31.0 microg/dl [range, undetectable (< 10 microg/dl) to 98 microg/dl]. The rate of change in vitamin A concentrations (n = 180 children) did not vary significantly by any factor other than baseline vitamin A concentration. Baseline vitamin A concentration was not associated with morbidity (incidence of infections, growth failure, CD4+ percent decline below 15%, increases in serum HIV RNA concentrations above either 10(5) or 10(6) copies/ml or acute care hospitalization). Neither baseline vitamin A concentration nor the rate of change of vitamin A concentrations was associated with mortality.

CONCLUSIONS

Among these North American children with relatively normal vitamin A concentrations, vitamin A was not observed to be associated with morbidity or mortality.

Serum HIV-1 p24 antibody, HIV-1 RNA copy number and CD4 lymphocyte percentage are independently associated with risk of mortality in HIV-1-infected children. National Institute of Child Health and Human Development Intravenous Immunoglobulin Clinical Trial Study Group

OBJECTIVE

The role of HIV-1 antibody in modulating disease progression must be assessed in the context of other immune and viral load markers. We evaluated the association between HIV-1 p24 antibody, HIV-1 RNA, immune complex-dissociated (ICD) p24 antigen, CD4 cell percentage, and mortality in a cohort of 218 HIV-infected children enrolled in a trial of intravenous immunoglobulin prophylaxis of bacterial infections.

METHODS

CD4 cell percentage was measured and sera collected and stored at baseline and every 3 months on study (1988-1991). Stored sera were assayed for HIV-1 p24 antibody, HIV-1 RNA, and ICD p24 antigen. Mortality was recorded during the trial and updated through 1996 (mean total follow-up, 6.3 years).

RESULTS

Eighty-one (37%) children died; probability of mortality for children with baseline HIV-1 p24 antibody concentrations of undetectable (< 1), 1-4, 5-124, and > or = 125 reciprocal titer units (RTU) was 61, 50, 24, and 10%, respectively. A 3.5-fold increase in the relative risk (RR) of death [95% confidence interval (CI), 2.2-5.5] was observed among children with baseline HIV-1 p24 antibody concentration < 5 RTU compared with > or = 5 RTU. In multivariate analyses, p24 antibody, HIV-1 RNA, and CD4 cell percentage but not ICD p24 antigen were independently associated with mortality; the RR of death increased by 1.7 (95% CI, 1.3-2.1) for each log10 decrement in baseline HIV-1 p24 antibody.

CONCLUSIONS

HIV-1 p24 antibody, HIV-1 RNA and CD4 cell percentage independently predict mortality amongst infected children. Whereas CD4 cell percentage provides an estimate of the general degree of immune suppression, HIV-1 p24 antibody could provide an easily obtained, inexpensive assessment of CD4 cell function and could augment prognostic information provided by CD4 cell count and viral load for clinical management of infected children.

Disease progression in a cohort of infants with vertically acquired HIV infection observed from birth: the Women and Infants Transmission Study (WITS)

BACKGROUND

The Women and Infants Transmission Study is an ongoing prospective cohort study of HIV-infected pregnant women and their infants. We used the 1994 U.S. Centers for Disease Control and Prevention (CDC) classification system for HIV infection in children to describe HIV disease progression in 128 HIV-infected children, and examined maternal and infant characteristics associated with disease course.

METHODS

The Kaplan-Meier method was used to calculate probabilities of entry into CDC clinical classes A, B, and C (mild, moderate, and severe HIV disease); CDC immunologic stages 2 and 3; and death. Relative risks of progression for selected predictor events were estimated using the Cox proportional hazards model.

RESULTS

With a median 24 months of follow-up, the median ages at entry into clinical classes A, B and C were 5, 11, and 48 months, respectively. Increased risk of progression to class C was seen in infants who had: onset of class B events (p < .001); progression to immunologic stage 2 (p < .001) or 3 (p < .001); early culture positivity (in first 48 hours, p < .01; in first 7 days, p = .03); and early appearance (within the first 3 months of life) of lymphadenopathy, hepatomegaly, or splenomegaly (p < .001).

CONCLUSIONS

Reaching specific clinical or immunologic stages were strong predictors of progression to AIDS or death. Early onset of clinical signs (onset of lymphadenopathy, hepatomegaly, or splenomegaly < or =3 months of age), and early culture positivity (within the first 48 hours or within the first week of life), defined the infant with highest risk of disease progression.

Encephalopathy and progression of human immunodeficiency virus disease in a cohort of children with perinatally acquired human immunodeficiency virus infection. Women and Infants Transmission Study Group

OBJECTIVE

To describe the incidence, predictors, and survival of children with human immunodeficiency virus (HIV) encephalopathy followed in the Women and Infants Transmission Study cohort.

STUDY DESIGN

Retrospective review of clinical and immunologic staging of perinatally HIV-infected infants, based on the 1994 Centers for Disease Control and Prevention Classification System.

RESULTS

Data were available for 128 HIV-infected children, with a median follow-up of 24 months. HIV encephalopathy was diagnosed in 27 (21%) of children. Median survival after diagnosis was 14 months. Of children with encephalopathy, 74% had at least moderate immunosuppression by the time of diagnosis. Encephalopathy represented the first acquired immunodeficiency syndrome-defining condition in 67%, and the only one in 26% of children. Hepatosplenomegaly or lymphadenopathy during the first 3 months of life was diagnosed in 63%, in contrast to 29% of those without encephalopathy (p value = 0.001). Cardiomyopathy was present in 30% of the children with encephalopathy versus 2% of those without encephalopathy. High viral load in infancy was associated with increased risk of encephalopathy but was not predictive of age at onset.

CONCLUSIONS

Encephalopathy in children with HIV is common and is associated with high viral load, immunodeficiency, and shortened survival. Encephalopathy was more likely to develop in infants with early signs and symptoms of HIV, although age at onset could not be predicted.

The immunogenicity of Haemophilus influenzae type b conjugate vaccines in children born to human immunodeficiency virus-infected women. Women and Infants Transmission Study Group

BACKGROUND

Immunocompromise caused by HIV-1 infection increases the importance of receipt of routine childhood vaccines to prevent infections such as invasive Haemophilus influenzae type B (Hib) disease. The objectives of the study were to evaluate the immunogenicity of Hib conjugate vaccines among HIV-infected children according to clinical and immunologic disease progression as well as viral load.

METHODS

The concentration of antibody to polyribosylribitol phosphate (PRP) was measured at approximately 9 and 24 months of age in plasma specimens from children of HIV-infected women enrolled in the Women and Infants Transmission Study.

RESULTS

Among 227 children (35 HIV-infected, 192 uninfected) at the 9-month study visit who were known to have received age-appropriate immunization with CRM197 mutant Corynebacterium diphtheriae protein-conjugated Hib vaccine, geometric mean antibody concentrations were lower among HIV-infected children (1.64 microg/ml) than among uninfected children (2.70 microg/ml), although the difference was not statistically significant. Anti-PRP antibody concentrations did not vary significantly among these HIV-infected children with predominantly mild-moderate disease progression according to clinical category, immunologic stage or viral load (P > or = 0.48). The proportion of children with antibody concentrations > or = 1.0 microg/ml did not vary significantly according to HIV infection status (73% uninfected, 74% infected) or, if infected, clinical or immunologic disease progression or viral load. Similar results were obtained among 127 children (17 HIV-infected, 110 uninfected) eligible for analysis at the 24-month study visit. Changes in antibody concentrations over time (between 9 and 24 months of age) did not differ significantly among 10 HIV-infected as compared with 72 uninfected children (P=0.81).

CONCLUSIONS

These results suggest that HIV-infected children with predominantly mild-moderate disease progression respond reasonably well in terms of a quantitative antibody response to Hib conjugate vaccines during the first 2 years of life. Research to further characterize the immune response to Hib conjugate vaccines and to further delineate the "durability" of anti-PRP antibody concentrations beyond 2 years of life should be pursued.

Assessing human risk to heterocyclic amines

Heterocyclic amines such as MeIQx and PhIP are potent genotoxic chemicals which are formed at part per billion levels when meat is cooked. Using assays based on gas chromatography/mass spectrometry with stable isotope labelled analogues as internal standards we have demonstrated MeIQx and PhIP, are efficiently absorbed into the systemic circulation after ingestion of fried beef. Using a potent and selective inhibitor of human CYP1A2, furafylline, we have shown that N-hydroxylation catalysed by this enzyme is the major pathway of metabolism of MeIQx and PhIP and is solely responsible for their oxidation to mutagenic species. This is in contrast to the situation in laboratory animals in which both activation by N-hydroxylation and deactivation by C-oxidation occurs. When furafylline was administered to human volunteers before ingestion of fried beef, we showed that > 90% of MeIQx and approximately 70% of PhIP elimination could be inhibited, demonstrating the extent to which activation occurred in man. MeIQx is a very powerful mutagen in bacterial assays whereas PhIP is a more potent mammalian cell mutagen. Using a mammalian cell target gene, hprt, we have shown that PhIP induces a characteristic mutational 'fingerprint' which is identical to that detected in the Apc gene of 5/8 colonic tumours induced by PhIP in rats. These studies support a biological association between HA exposure and diet-related tumours but emphasise that information obtained from animal studies does not always reflect the situation in humans.

Viral load and disease progression in infants infected with human immunodeficiency virus type 1. Women and Infants Transmission Study Group

BACKGROUND

There are only limited data on human immunodeficiency virus type 1 (HIV-1) RNA in perinatally infected infants. Understanding the dynamics of HIV-1 infection and its relation to disease progression may help identify opportunities for effective antiviral treatment in infected infants.

METHODS

We obtained plasma samples from 106 HIV-infected infants at birth; at 1, 2, 4, 6, 9, 12, 15, and 18 months of age; and subsequently every 6 months. HIV-1 RNA was assayed by means of a reverse-transcription polymerase chain reaction. The infants were born between 1990 and 1993, and only 21 percent of the infants' mothers received any treatment with zidovudine during pregnancy.

RESULTS

Plasma HIV-1 RNA levels increased rapidly after birth, peaked at 1 to 2 months of age (median values at 1 and 2 months, 318,000 and 256,000 copies per milliliter, respectively), and then slowly declined to a median of 34,000 copies per milliliter at 24 months. Newborns with a first positive HIV-1 culture within 48 hours after birth had significantly higher HIV-1 RNA levels, although only during the first two months of life, than those with a first positive culture seven or more days after birth. Infants with a rapid progression of disease had higher peak HIV-1 RNA levels in the first two months of life than those without rapid progression (median value, 724,000 vs. 219,000 copies per milliliter; P=0.006), as well as a higher geometric mean value during the first year of life (median value, 330,000 vs. 158,000 copies per milliliter, P=0.001).

CONCLUSIONS

In perinatally infected infants, HIV-1 RNA levels are high and decline only slowly during the first two years of life. Infants with very high viral loads in the first months of life are at increased risk for a rapid progression of disease, which suggests that early treatment with antiretroviral agents may be indicated for these infants.

The relationship between serum human immunodeficiency virus type 1 (HIV-1) RNA level, CD4 lymphocyte percent, and long-term mortality risk in HIV-1-infected children. National Institute of Child Health and Human Development Intravenous Immunoglobulin Clinical Trial Study Group

Association of human immunodeficiency virus type 1 (HIV-1) RNA level, CD4 cell percent, and mortality was examined in stored sera from 254 infected children in an intravenous immunoglobulin infection prophylaxis trial. Ninety-two children (36.2%) died (41 during the study, 51 during long-term follow-up). The geometric mean baseline HIV-1 RNA level was 104,626 copies/mL, and the mean CD4 cell percent was 25%. Relative risk of death (RR) was 2.1 if the baseline RNA level was >100,000 copies/mL (95% confidence interval [CI], 1.4-3.0) and was 3.0 if the baseline CD4 cell percent was <15% (95% CI, 2.2-4.0). If RNA levels increased after baseline, the RR was 1.8 (95% CI, 1.3-2.6), and if the CD4 cell percent dropped to <15%, the RR was 2.8 (95% CI, 1.6-4.9). In a multivariate model, both baseline RNA level and CD4 cell percent were independently associated with mortality risk. In a time-dependent model, the RR per log10 increase in HIV-1 RNA copy numbers was 2.8 (95% CI, 2.1-3.6) and per 5 percentage point decrement in CD4 cell percent was 1.3 (95% CI, 1.2-1.5). Both variables should be considered for in decision-making regarding therapy and evaluation of antiretroviral response.

The utility of IgA antibody to human immunodeficiency virus type 1 in early diagnosis of vertically transmitted infection. National Institute of Allergy and Infectious Diseases and National Institute of Child Health and Human Development Women and Infants Transmission Study Group

OBJECTIVE

To determine the sensitivity and specificity of anti-human immunodeficiency virus (HIV) IgA in identifying infected infants at or before 6 months of age among the offspring of HIV-infected mothers.

DESIGN

Prospective comparison of anti-HIV IgA measurement performed in 2 different laboratories by 2 different methods with the criterion standard of blood culture.

SETTING

Five centers in the United States and Puerto Rico.

PATIENTS

Population-based sample of 156 infants of HIV-infected mothers in the Women and Infants Transmission Study.

MAIN OUTCOME MEASURES

Results of anti-HIV IgA test in relation to the infection status of the infants as measured by blood culture.

RESULTS

Six-month plasma or serum samples were first tested in the 2 laboratories. The sensitivity and specificity of anti-HIV IgA in detecting infected infants at this age by laboratories 1 and 2 were 69% and 63% and 100% and 99%, respectively. A look-back study of samples obtained at birth, 1, 2, and 4 months was then performed on all infected children and a matched set of uninfected children. The performance of the test at birth was unsatisfactory in both laboratories (sensitivity 44% and 33%, specificity 43% and 60%), whether peripheral or cord blood was examined. At 1, 2, and 4 months, the sensitivity of the test was lower than at 6 months, but specificity was high. A modest correlation of absent anti-HIV IgA antibody and low percentage of CD4 cells in peripheral blood was seen at 6 months of age.

CONCLUSIONS

The anti-HIV IgA test has moderate sensitivity and high specificity for the diagnosis of HIV infection at 6 months of age in the offspring of infected mothers.

Blood culture in the first 6 months of life for the diagnosis of vertically transmitted human immunodeficiency virus infection. The Women and Infants Transmission Study Group

Serial blood cultures over the first 6 months of life in 310 infants with vertical exposure to human immunodeficiency virus (HIV) in the Women and Infants Transmission Study were analyzed to determine their value for early diagnosis of HIV infection. Cultures were done at 0-7 days and 1, 2, 4, and 6 months of age: 55 infants were infected. Blood culture sensitivity in infected children was 24% (7/29) during the first week of life and 85%, 91%, 82%, and 88%, respectively, at 1, 2, 4, and 6 months. The sensitivity, specificity, and positive and negative predictive values of a single culture between 1 and 6 months of age were, respectively, 86.9%, 99.6%, 97.9%, and 97.5%. Two negative cultures between 1 and 6 months of age defined an uninfected infant with a specificity of 99.2%-100.0%. Blood culture done between 1 and 6 months of age in children of HIV-positive mothers is a sensitive and specific test for HIV infection, with high positive and negative predictive values.

A phenotypic study of CD8+ lymphocyte subsets in infants using three-color flow cytometry

Flow cytometry is a powerful tool for the multiparametric evaluation of cell surface phenotype in patients with HIV disease. Many cell surface molecules can be evaluated by three-color flow cytometry and the markers correlated with functional activity. It has recently been recognized in adults that the CD8 cell is an important lymphocyte subset in HIV disease that correlates with disease outcome, but there is little information about CD8 subsets in infants. Therefore, we studied infants born to HIV-infected mothers and those born to uninfected mothers. No significant differences were seen in phenotypic markers of activation (CD38, HLA-DR), maturation (CD45RO, CD45RA), and function (CD28) between uninfected infants born to HIV infected or uninfected mothers. In HIV-infected infants, a substantial increase in CD8+ CD38+ HLA-DR+ expression was seen. In addition, we found that there was a significant increase in the CD8+ CD45RO+ CD45RA- subset which is characteristic of the memory phenotype. Finally, evaluation of CD28 (costimulatory molecule involved in T cell activation), which is expressed on almost all CD8 cells at birth, showed that this population was significantly reduced in infected infants. These studies suggest that three-color flow cytometry is a powerful tool for evaluating phenotypic changes in lymphocyte subsets and enhancing our understanding of the pathobiology of HIV disease.

Cytochrome P450 in highly purified suspension of nonparenchymal liver cells

Rat liver nonparenchymal cells (NPC) were prepared by pronase digestion and purified on discontinuous gradients on Nycodenz. Morphological and biochemical characterization of cell suspensions showed that they were free of contamination by hepatocytes. We have confirmed the usefulness of pyruvate kinase activity in monitoring the degree of hepatocyte contamination of NPC and we have derived an equation which allows this carry-over to be calculated. Using highly purified suspensions of NPC we have shown that they contain glucose-6-phosphatase in low but detectable levels. Spectrophotometric studies showed that they contain cytochrome P450, with a specific content of 24 +/- 5 pmole mg-1 cell protein. A potential source of error in previous studies was recognized; namely that peroxidase, present in NPC in high concentration, is able to mask the absorption due to cytochrome P450. Both the presence and inducibility of this enzyme in NPC prepared from rats pretreated with phenobarbital or 3-methylcholanthrene have been confirmed using Western blot analysis.

Localization of muscle gene products in nuclear domains

The localization of gene products is central to the development of cell polarity and pattern specification during embryogenesis. To monitor the distribution of gene products encoded by different nuclei in the same cell in tissue culture, we fused cells of different species to form multinucleated non-dividing heterokaryons. In previous fusion studies, cell-surface antigens and organelles contributed by disparate cell types intermixed within minutes. Using heterokaryons produced with differentiated muscle cells, we demonstrate here that a muscle membrane component, the Golgi apparatus mediating its transport, and a sarcomeric myosin heavy chain are localized in the vicinity of the nuclei responsible for their synthesis. These results provide direct evidence that products (organelle, membrane and structural proteins) derived from individual nuclei can remain localized in myotubes, a finding with implications both for neuromuscular synapse formation and for the carrier state of Duchenne muscular dystrophy.

Pustulosis palmaris et plantaris: its association with chronic recurrent multifocal osteomyelitis

Palmoplantar pustules may rarely be associated with chronic recurrent multifocal osteomyelitis in children and young adults. Additional features of this disorder are recurrent low-grade fevers and bone pain. Skeletal radiographs and bone films suggest osteomyelitis, but bone cultures yield no growth of organisms. The cause of this disorder is unknown, and treatment remains unsatisfactory.

Hyper IgM immunodeficiency. A primary dysfunction of B lymphocyte isotype switching

Immunological evaluations (lymphocyte markers, B cell differentiation, T cell function) were performed on peripheral blood mononuclear cells from four individuals with hyper IgM immunodeficiency. Number, proportion, and proliferation of T lymphocytes and T lymphocyte subpopulations were relatively normal in affected individuals. The percentage and number of B cells expressing surface IgM and IgD were either normal or elevated in both blood and lymph nodes. However, surface IgG- and IgA-bearing B lymphocytes were completely absent. In vitro stimulation of blood lymphocytes with both T cell-dependent and T-cell independent polyclonal B cell activators resulted in normal numbers of IgM plasma cells and IgM secretion in cultures, but failed to induce any IgG- or IgA-producing cells. This failure of isotype switching was intrinsic to the B cell population and did not involve aberrant T cell help or suppression. Therefore, individuals with this disorder possess an intrinsic B cell dysfunction that is not related to abnormal T cell regulation.