Practice parameters for the diagnosis and management of immunodeficiency. The Clinical and Laboratory Immunology Committee of the American Academy of Allergy, Asthma, and Immunology (CLIC-AAAAI)

In this brief review, only the most useful immunologic tests available for defining host defects that lead to susceptibility to infection have been emphasized. It should be pointed out that those evaluations and tests ordered by the physician will rule out the vast majority of the currently recognized defects. Finally, it is important that any patients identified as abnormal by these screening tests be characterized as fully as possible in centers specializing in these diseases before therapy is initiated, since what may appear to be a simple diagnosis on the surface may be an indicator of more complex underlying problems.

Characteristics of children surviving to 5 years of age or older with vertically acquired HIV infection

The objective of this study was to examine characteristics of long-term survivors (aged 5 years or older) of vertical human immunodeficiency virus (HIV) infection. A retrospective cohort study design was employed. Forty-eight (68%) of 71 children who were born before 1990 and evaluated in our center survived to at least 5 years of age; 41 (58%) children remain alive (median age, 7.3 years). Only one (11%) of nine children with initial acquired immunodeficiency syndrome (AIDS)-defining conditions in the first year of life survived to age 5, whereas 47 (76%) of 62 children who did not have AIDS by age 1 year were alive at 5 years of age (p = .0003). Seventeen (43%) of 40 children with AIDS-defining conditions before age 5, and all 31 children without such conditions, survived to age 5 years (p = .000001). All eight children with lymphoid interstitial pneumonitis/pulmonary lymphoid hyperplasia (LIP/PLH) as their sole AIDS-defining condition survived to age 5. All 24 children who had neither an AIDS-defining condition nor severe immunosuppression by 5 years of age, and 24 (51%) of 47 children who had either or both of these findings, survived to age 5 years (p = .00008). To date, only 16 (39%) of 41 surviving children older than 5 years of age have had an AIDS-defining condition. However, true nonprogression of HIV disease (no clinical signs or symptoms; no evidence of immunosuppression) was unusual, occurring in only two (5%) of the same 41 children. In our center, most children with vertical HIV infection survive to at least 5 years of age, but the prognosis is not as good for those who experience an AIDS-defining condition or severe immunosuppression in the first 5 years of life.

Excess intrauterine fetal demise associated with maternal human immunodeficiency virus infection

A prospective study of transplacental transmission of human immunodeficiency virus (HIV) showed an increased rate of spontaneous fetal demise in HIV-seropositive mothers: 14 losses in 124 pregnancies. HIV was detected in placental and fetal tissues in 7 of 14 by in situ hybridization. The proportion of fetal infection far exceeded the transmission rate of 13% in liveborn babies. No association was seen between fetal transmission and a maternal history of drug abuse or coinfections; mothers with AIDS more often had fetal loss associated with HIV transmission than did asymptomatic mothers. In affected fetuses, HIV was detected in many tissues and was associated with thymic pathology. This suggests that maternal HIV infection increases the risk for pregnancy loss associated with HIV transmission. The possibility that HIV may be fetotoxic, that thymic dysfunction may interfere with pregnancy progression, or that the intrauterine milieu in HIV-seropositive pregnancies may be unfavorable (or a combination of factors) should be considered.

Transport of recombinant human CD4-immunoglobulin G across the human placenta: pharmacokinetics and safety in six mother-infant pairs in AIDS clinical trial group protocol 146

Recombinant CD4-immunoglobulin G (rCD4-IgG) is a 98-kDa human immunoglobulin-like protein that is produced by fusing the gp120 binding domain of CD4 to the Fc portion of the human IgG1 heavy chain. This hybrid molecule was given to human immunodeficiency virus (HIV)-infected pregnant women at the onset of labor by intravenous bolus at 1 mg/kg of body weight (group A; n = 3) and 1 week prior to and at the onset of labor by the same route and at the same dose (group B; n = 3). In addition to pharmacokinetic studies, safety in the mothers and infants was determined through routine chemistries, hematology, and urinalysis; immunologic and HIV infection statuses in the infants were assessed through lymphocyte cultures, p24 antigen level determination, culture of HIV from plasma, PCR, lymphocyte subset enumeration, quantitative immunoglobulin analysis, and lymphocyte proliferation. Thirty minutes after the rCD4-IgG injection, concentrations in maternal serum were 12 to 23 micrograms/ml. These concentrations declined slowly, with initial and terminal half-lives (mean +/- standard deviation) of 9.95 +/- 3.23 and 47.6 +/- 22.3 h, respectively. Infants were born 2.6 to 46.5 h after rCD4-IgG administration; concentrations of rCD4-IgG in cord blood ranged from 28 to 107 ng/ml. The half-life of rCD4-IgG in infants ranged from 5 to 29 h. These data demonstrate that the transfer of rCD4-IgG from the mother to the fetus is rapid and that newborns do not appear to have any difficulty eliminating rCD4-IgG. No safety concerns in mothers or infants were encountered. Although the study did not address the question of efficacy, none of the infants was HIV type 1 infected 36 months later. In summary, these findings document that bifunctional immune molecules can be transported across the placenta, and this general approach may be used in the future to block vertical transmission of HIV type 1.

Early detection of HIV in infants: aspects of design and analysis for diagnostic test studies

OBJECTIVE

To review investigations on the early detection of HIV infection in infants to determine adherence to traditional methods of study design and analysis for evaluating new laboratory tests.

DATA SOURCES

A National Library of Medicine (MEDLINE) search was conducted to identify such investigations through 1993. Cited references in identified manuscripts were also considered. The search was restricted to investigations of human subjects and those published in the English language.

STUDY SELECTION

Final inclusion criteria included (1) report of the age and human immunodeficiency virus (HIV) infection status of the subjects at the time of the diagnostic testing, and (2) presentation of data allowing confirmation of presented analyses and additional analyses.

DATA EXTRACTION

Criteria for judging the investigations included (1) whether the criteria used to determine the positive and negative test results were defined; (2) whether the necessary sample size for the study was calculated; (3) whether the patients studied were representative of the patients to whom the test would be applied; (4) whether a gold standard evaluation was performed; (5) whether the outcomes included in the analyses were independent; (6) whether the test characteristics were properly analyzed; and, (7) whether confidence intervals were presented.

DATA SYNTHESIS

An informative presentation of a diagnostic test should include as a minimum the seven criteria listed above. Only 21 of 36 (58%) of the studies incorporated at least three of the criteria.

CONCLUSIONS

There is a wide variation in the manner in which investigations of diagnostic tests are conducted and the results reported. Increased awareness and use of standard study designs and analyses will allow the application of metanalyses. Such analyses will help guide the direction taken for finding and establishing early diagnostic procedures for HIV infection at birth or during infancy.

Sensitivity of immune complex-dissociated p24 antigen testing for early detection of human immunodeficiency virus in infants

Several investigators have suggested that early diagnosis of human immunodeficiency virus (HIV) infection in infants could be accomplished with a modified, more-sensitive, acid-dissociated p24 antigen enzyme-linked immunosorbent assay (ELISA) technique (p24 antigen immune complex dissociation [ICD]). We compared detection of HIV infection by HIV culture, PCR, and p24 antigen ICD assays in 46 infants by using samples collected independently. The detection sensitivity of the p24 antigen ICD assay was 0% with cord blood samples (2 HIV-positive infants), 38% with plasma samples from infants under 3 months of age (8 HIV-positive infants), and 58% overall (12 HIV-positive infants). By contrast, the sensitivities of HIV culture and PCR were 50% for cord blood samples, 75% for plasma samples from infants under 3 months of age, and 83% overall. These results indicate that the p24 antigen ICD does not offer the sensitivity necessary for this assay to be used as an indicator of HIV infection in infants.

Platelet-activating factor induces the tyrosine phosphorylation and activation of phospholipase C-gamma 1, Fyn and Lyn kinases, and phosphatidylinositol 3-kinase in a human B cell line

Platelet-activating factor (PAF) is a versatile lipid mediator of inflammation in a variety of biologic systems. We have previously reported that one of the earliest events in the signal transduction pathway of PAF in a human B lymphoblastoid cell line was the induction of tyrosine kinase activity concomitant with the activation of phospholipase C (PLC). We now demonstrate the occurrence of multiple tyrosine phosphorylation-dependent events which follow the interaction of PAF with its receptor on B cells. Anti-phosphotyrosine immunoprecipitates from lysates of PAF-stimulated cells, when fractionated by SDS-PAGE and analyzed by Western blotting with anti-PLC-gamma 1, showed that maximal tyrosine phosphorylation of this enzyme occurred within 2 min of stimulation. This phenomenon was verified by immunoprecipitating with anti-PLC-gamma 1 and subsequently probing with anti-phosphotyrosine. Immunoprecipitation of the tyrosine kinases, Fyn and Lyn, from PAF-stimulated cells, and use of these immunoprecipitates in kinase assays established that the activation of both kinases also occurred within the first 2 min of stimulation with phosphorylation occurring on their tyrosine residues. Additionally, we also provide evidence for the tyrosine phosphorylation of the p85 subunit of phosphatidylinositol 3-kinase (PtdIns 3-kinase) and activation of this kinase by PAF in a dose-dependent manner, maximal activation occurring within 10 min post-stimulation. We have thus demonstrated that the activation of tyrosine kinases is an important proximate step in PAF-mediated signal transduction in B cells, leading to tyrosine phosphorylation and activation of PLC-gamma 1, Fyn and Lyn kinases, and PtdIns 3-kinase.

Platelet-activating factor induces the tyrosine phosphorylation and activation of phospholipase C-gamma 1, Fyn and Lyn kinases, and phosphatidylinositol 3-kinase in a human B cell line

Platelet-activating factor (PAF) is a versatile lipid mediator of inflammation in a variety of biologic systems. We have previously reported that one of the earliest events in the signal transduction pathway of PAF in a human B lymphoblastoid cell line was the induction of tyrosine kinase activity concomitant with the activation of phospholipase C (PLC). We now demonstrate the occurrence of multiple tyrosine phosphorylation-dependent events which follow the interaction of PAF with its receptor on B cells. Anti-phosphotyrosine immunoprecipitates from lysates of PAF-stimulated cells, when fractionated by SDS-PAGE and analyzed by Western blotting with anti-PLC-gamma 1, showed that maximal tyrosine phosphorylation of this enzyme occurred within 2 min of stimulation. This phenomenon was verified by immunoprecipitating with anti-PLC-gamma 1 and subsequently probing with anti-phosphotyrosine. Immunoprecipitation of the tyrosine kinases, Fyn and Lyn, from PAF-stimulated cells, and use of these immunoprecipitates in kinase assays established that the activation of both kinases also occurred within the first 2 min of stimulation with phosphorylation occurring on their tyrosine residues. Additionally, we also provide evidence for the tyrosine phosphorylation of the p85 subunit of phosphatidylinositol 3-kinase (PtdIns 3-kinase) and activation of this kinase by PAF in a dose-dependent manner, maximal activation occurring within 10 min post-stimulation. We have thus demonstrated that the activation of tyrosine kinases is an important proximate step in PAF-mediated signal transduction in B cells, leading to tyrosine phosphorylation and activation of PLC-gamma 1, Fyn and Lyn kinases, and PtdIns 3-kinase.

Cytokine regulation by platelet-activating factor in a human B cell line

TNF-alpha is an inflammatory cytokine produced by B cells that also impacts B cell differentiation and Ig secretion. We have investigated the regulation of the TNF-alpha gene in a human B cell line in response to platelet-activating factor (PAF), a potent phospholipid often produced in inflammatory reactions. We report here that PAF increases the RNA levels for the TNF-alpha gene in the human B cell line Ramos. This is mediated by an increase in the transcription rate and a longer half-life of the TNF-alpha transcripts. Induction of the TNF-alpha gene is rapid in these cells and independent of new protein synthesis. Despite increasing RNA for the TNF-alpha gene, PAF increases TNF-alpha protein levels only in the presence of a costimulus, such as PMA. We hypothesize that PAF acts at the transcriptional level to increase TNF-alpha RNA, but a post-transcriptional block acts to regulate protein production. We also report that PAF enhances PMA-induced TNF-alpha production from human peripheral B cells. This increase is maximal at 0.1 microM PAF and is blocked by PAF receptor antagonists. The ability of PAF to modulate cytokine production from human B cells provides further evidence that PAF has a role in B cell biology and suggests it may be important in conditions involving B cell-derived cytokines.

Cytokine regulation by platelet-activating factor in a human B cell line

TNF-alpha is an inflammatory cytokine produced by B cells that also impacts B cell differentiation and Ig secretion. We have investigated the regulation of the TNF-alpha gene in a human B cell line in response to platelet-activating factor (PAF), a potent phospholipid often produced in inflammatory reactions. We report here that PAF increases the RNA levels for the TNF-alpha gene in the human B cell line Ramos. This is mediated by an increase in the transcription rate and a longer half-life of the TNF-alpha transcripts. Induction of the TNF-alpha gene is rapid in these cells and independent of new protein synthesis. Despite increasing RNA for the TNF-alpha gene, PAF increases TNF-alpha protein levels only in the presence of a costimulus, such as PMA. We hypothesize that PAF acts at the transcriptional level to increase TNF-alpha RNA, but a post-transcriptional block acts to regulate protein production. We also report that PAF enhances PMA-induced TNF-alpha production from human peripheral B cells. This increase is maximal at 0.1 microM PAF and is blocked by PAF receptor antagonists. The ability of PAF to modulate cytokine production from human B cells provides further evidence that PAF has a role in B cell biology and suggests it may be important in conditions involving B cell-derived cytokines.

Cyclosporin A blocks induction of tumor necrosis factor-alpha in human B lymphocytes

The effects of cyclosporin A (CSP) on tumor necrosis factor-alpha (TNF-alpha) RNA levels and protein production in human B cells and a B cell line were studied. The ability of CSP to block induction of RNA was compared to its inhibition of protein production in response to anti-IgM, phorbol ester (PMA) and platelet-activating factor (PAF). PAF is a phospholipid which has recently been found to activate human B cells. CSP blocks PAF-induced TNF-alpha RNA from the Ramos cell line, as well as inhibiting the enhancement of TNF protein production from both freshly isolated and Ramos B cells. CSP also blocks anti-Ig induced TNF-alpha RNA and protein but does not inhibit PMA-induced TNF-alpha. We conclude that B cells, like T cells, have CSP-independent and CSP-dependent signaling pathways and that PAF signaling is dependent upon a CSP-sensitive factor.

Association between anti-human immunodeficiency virus type 1 (HIV-1) antibody-dependent cellular cytotoxicity antibody titers at birth and vertical transmission of HIV-1

Because vertical transmission of human immunodeficiency virus type 1 (HIV-1) from mother to infant occurs in only 15%-35% of possible opportunities, natural immune defenses of the mother, fetus, or neonate may be protective against infection. The relation between antibody-dependent cellular cytotoxicity (ADCC) antibodies and HIV-1 infection was explored in 78 neonates born to HIV-infected women. More than 90% of sera had measurable ADCC titers against HIV-1IIIB. Infant titers were closely correlated with maternal titers but were independent of total IgG and total antibody reactive to the same strain in whole virus ELISA. At birth, mean ADCC antibody levels of infants or their mothers were the same for infants who were infected and those who ultimately seroreverted and remained healthy. ADCC antibody titers against HIV-1SF2 were weakly correlated with anti-HIV-1IIIB titers and did not predict protection from HIV-1 infection. High levels of anti-HIV-1 ADCC antibody at birth are not protective against vertical transmission of HIV-1.

Laboratory aspects of immunology

The field of clinical immunology is advancing rapidly and will continue to grow and benefit from the knowledge gained in different areas of basic immunology. The diagnosis and evaluation of a child with a suspected primary immune defect can be a challenging task that should be done carefully using the best available laboratory resources. Simple laboratory screening tests, available to most pediatricians, can be done initially and will provide an idea of the level of general immune competence. Referral for a more detailed evaluation should be made in selected cases. A basic understanding of the tests used in immune evaluation, as well as the fact that the results may be affected by multiple variables, is important. Of equal significance is the interaction of the physician with the laboratory in which the samples will be analyzed. Proper sample collection and handling as well as prompt processing by the laboratory are crucial. Equally important is the physician's interpretation of results in the context of the pediatric population. Tests like lymphocyte studies, WBC studies, immunoglobulin subclasses, response to antigenic challenge, and certain complement assays require a higher degree of expertise and should only be sent to laboratories with experience in performing them. Physicians need to gain confidence in the power of diagnosis that the immunology laboratory brings to their patients.

Differential effects of interleukin-2 and interleukin-4 on immunomodulatory role of platelet-activating factor in human B cells

Platelet-activating factor (PAF), a naturally occurring phospholipid cytokine, is a potent mediator of allergic and inflammatory reactions, as well as a modulator of immune responses. In the present study we showed that PAF is involved in early B-cell activation, as demonstrated by the increased cyclic AMP (cAMP) generation by PAF in a time- and dose-dependent manner in anti-mu antibody- plus B-cell growth factor-activated normal human peripheral blood B lymphocytes. PAF also regulated differentiation by causing a biphasic response on immunoglobulin M (IgM) production with an inhibitory signal generated at 10(-6) M and a stimulatory signal generated at 10(-8) to 10(-10) M. PAF enhanced IgA secretion. The regulation exerted by PAF was shown to be specific because the addition of the PAR antagonist CV-3988 abrogated these effects and the inactive form of PAF, lyso-PAF, induced neither cAMP generation nor immunoglobulin secretion in normal human B cells. Other cytokines, interleukin-2 (IL-2) and IL-4, potent mediators of the immune response, were unable to elicit a cAMP response in B cells. However, the addition of PAF (10(-6) M) with wither IL-2 or IL-4 enhanced cAMP production above the levels enhanced by the addition of PAF alone. IL-2 or IL-4, individually, stimulated IgM production, yet costimulation with PAF resulted in a differential effect between IL-2 and IL-4. PAF down-regulated the IL-4-induced IgM secretion, whereas the IL-2-induced IgM secretion was enhanced. The presence of CV-3988 returned all valued to those obtained with IL-2 or IL-4 alone, demonstrating the specificity of PAF. These data suggest that PAF is an important B-cell immunomodulator which can interact with other leukocyte cell mediators.

Activation of NF-kappa B and immunoglobulin expression in response to platelet-activating factor in a human B cell line

Nuclear factor kappa B (NF-kappa B) has been shown to be an important transcriptional regulatory protein in multiple cell types in response to a number of physiological signals. In lymphocytes it has been implicated in transcriptional regulation of the kappa light chain, MHC, IL-6, and IL-2 receptor genes, depending on the differentiation state of the cell. In the present study we demonstrate that platelet-activating factor (PAF), a phospholipid molecule, activates NF-kappa B and increases kappa light chain mRNA in a human B cell line. Treatment of Ramos cells with PAF (10(-9) to 10(-6) M) increased RNA levels of the NF-kappa B p50 precursor, known as p105, in a dose-dependent manner. p105 RNA levels increased to a maximum observed at 8-10 hr and then diminished by 24 hr; this induction was not blocked by cycloheximide (CHX). PAF induced nuclear kappa B binding at similar concentrations, but more rapidly, attaining maximal levels within 15 min. CHX did not block this activity either. PAF treatment of Ramos cells also resulted in increased levels of RNA for kappa light chain. These results suggest that PAF activates NF-kappa B by at least two mechanisms in these cells, one at the level of post-translational protein activation and the other by increasing the level of RNA for NF-kappa B p105.

A comparative study of human immunodeficiency virus culture, polymerase chain reaction and anti-human immunodeficiency virus immunoglobulin A antibody detection in the diagnosis during early infancy of vertically acquired human immunodeficiency virus infection

The infection status of 91 infants born to mothers with human immunodeficiency virus (HIV) infection was determined. Twenty-eight (31%) infants had confirmed HIV infection and 63 (69%) had seroreverted to HIV and lack evidence of infection. During the first 6 months of life HIV culture had a sensitivity and specificity for diagnosis of HIV infection of 80 and 100%, respectively. False negative HIV cultures were observed in only 7 of 35 specimens, 6 from among the 12 infected infants tested at birth. The sensitivity and specificity of polymerase chain reaction (PCR) detection of HIV were 95 and 93% respectively. A single false negative PCR test result was observed among the 19 tests performed on specimens from HIV-infected infants. False positive PCR test results were observed occasionally throughout the first 6 months of life. Detection of HIV-specific IgA antibody lacked diagnostic sensitivity; positive test results were observed in only 53% of specimens obtained from infected infants. Culture and PCR detection offer excellent sensitivity and specificity for diagnosis of HIV infection during the first 6 months of life; however, false-negative HIV cultures sometimes are observed, particularly during the newborn period, and either false negative or false positive PCR test results may be noted occasionally. For purposes of clinical decision-making, any positive test result should be confirmed with a second HIV culture or PCR test performed on a separate blood specimen.

Okadaic acid inhibits dephosphorylation of cytoplasmic p53 during lymphocyte activation

A competition radioimmunoassay specific for conserved Domain V of p53 revealed that Domain V was masked in highly phosphorylated cytosolic p53 of resting T lymphocytes and unmasked through dephosphorylation during lymphocyte activation. Phosphatase type 2A was shown to act upon immunopurified p53 in a manner that increased the immunoreactivity of the molecule in the Domain V RIA. Treatments of T cells with okadaic acid (1nM) prior to addition of Concanavalin-A/serum inhibited completely the dephosphorylation of cytosolic p53 observed to occur within 10-20min of stimulation. Brief exposure of T cells to okadaic acid during the first hour of activation by mitogens produced increased rates of cellular proliferation. Sustained inhibition of the dephosphorylation of cytoplasmic p53 in cells undergoing mitogenic stimulation may affect adversely the ability of p53 to exert its anti-proliferative effect and could contribute to unregulated cell growth.

Immunologic targets of HIV infection: T cells. NICHD IVIG Clinical Trial Group, and the NHLBI P2C2 Pediatric Pulmonary and Cardiac Complications of HIV Infection Study Group

One of the principal targets of HIV infection is the human peripheral blood CD4+ T cell, resulting in progressive CD4+ lymphocyte loss. Hypothesized mechanisms for this loss include apoptosis, cytolytic reactions, V-beta gene deletion of the T-cell receptor (TCR) by superantigens, CD4+ lymphocyte syncytium formation, and autoimmune reactions. In adults with HIV infection, the critical decline in CD4+ lymphocyte number that heralds the onset of AIDS-defining conditions is well characterized, whereas in infants and children the critical level of CD4+ cells predisposing to the development of AIDS-defining conditions or mortality is not fully characterized, due to an incomplete knowledge of CD4+ lymphocyte number and changes with age in normal and HIV-infected children. In a prospective study of 317 infants born to HIV-infected women, early results show that the monthly change in absolute CD4+ lymphocyte number over a 3- to 9-month period in HIV-infected infants was -109 cells/mm3 per month, at least double the rate of decline measured in HIV-noninfected infants in the study or that calculated from normal infants' values reported in the literature. In other clinical studies in HIV-infected infants and children, it was possible to study the effect of low CD4+ cell counts on clinical status and mortality. In HIV-infected pediatric patients younger than 1 year, it was possible to correlate low CD4+ cell number with advanced disease status (CDC pediatric class P-2). It was also possible to correlate extremely low CD4+ cell counts (< 200 cells/mm3) in HIV-infected children with a significant risk of mortality within the next 3 months of life. Sequential CD4+ cell analysis of HIV-high-risk infants will delineate the rate of HIV-related decline in CD4+ cells, thus facilitating the diagnosis of HIV infection and aiding in identification of HIV-infected children at high risk of disease progression or death.

Tyrosine phosphorylation of phospholipase C concomitant with its activation by platelet-activating factor in a human B cell line

Platelet-activating factor (PAF) is a powerful inflammatory mediator in a variety of systems. Upon binding its receptor on B lymphocytes, it activates phospholipases C and A2, thus initiating a cascade of events culminating in changes in the program of the target cell. We have now extended our previous studies of the effects of PAF on EBV-transformed human B cell lines to examine the mechanism by which phospholipase C (PLC) is activated. PAF-induced incorporation of 32P into phosphatidylinositol (PtdIns) was markedly diminished by the tyrosine kinase inhibitors, genistein, and those of the tyrphostin family, tyrphostins 25, 47, and 51. The generation of inositol phosphates induced by PAF was also significantly inhibited by these inhibitors. Correlating with this inhibition of PtdIns turnover, the elevation of intracellular calcium concentrations stimulated by PAF was observed to be inhibited in the presence of inhibitors of tyrosine kinases. In addition, the induction of expression of the proto-oncogene, c-fos, was substantially attenuated by these inhibitors. Finally, employing anti-phosphotyrosine immunoprecipitates of lysates from PAF-stimulated cells in an in vitro PLC assay, we have provided evidence for an increase in the tyrosine phosphorylation levels of PLC upon stimulation, and the inhibition of this increase by tyrosine kinase inhibitors. In summary, we have shown that in B cells tyrosine kinase activity is essential for the PtdIns turnover, the generation of inositol phosphates, and the calcium flux induced by PAF and that platelet-activating factor-induced tyrosine phosphorylation of PLC is likely to be required for the activation of this enzyme.

Tyrosine phosphorylation of phospholipase C concomitant with its activation by platelet-activating factor in a human B cell line

Platelet-activating factor (PAF) is a powerful inflammatory mediator in a variety of systems. Upon binding its receptor on B lymphocytes, it activates phospholipases C and A2, thus initiating a cascade of events culminating in changes in the program of the target cell. We have now extended our previous studies of the effects of PAF on EBV-transformed human B cell lines to examine the mechanism by which phospholipase C (PLC) is activated. PAF-induced incorporation of 32P into phosphatidylinositol (PtdIns) was markedly diminished by the tyrosine kinase inhibitors, genistein, and those of the tyrphostin family, tyrphostins 25, 47, and 51. The generation of inositol phosphates induced by PAF was also significantly inhibited by these inhibitors. Correlating with this inhibition of PtdIns turnover, the elevation of intracellular calcium concentrations stimulated by PAF was observed to be inhibited in the presence of inhibitors of tyrosine kinases. In addition, the induction of expression of the proto-oncogene, c-fos, was substantially attenuated by these inhibitors. Finally, employing anti-phosphotyrosine immunoprecipitates of lysates from PAF-stimulated cells in an in vitro PLC assay, we have provided evidence for an increase in the tyrosine phosphorylation levels of PLC upon stimulation, and the inhibition of this increase by tyrosine kinase inhibitors. In summary, we have shown that in B cells tyrosine kinase activity is essential for the PtdIns turnover, the generation of inositol phosphates, and the calcium flux induced by PAF and that platelet-activating factor-induced tyrosine phosphorylation of PLC is likely to be required for the activation of this enzyme.

Study of human immunodeficiency virus resistance to 2'-3'-dideoxyinosine and zidovudine in sequential isolates from pediatric patients on long-term therapy

Resistance to zidovudine (3'-azido-3'-deoxythymidine) and 2',3'-dideoxyinosine (ddI) has been reported for human immunodeficiency virus (HIV) isolates from adults, but little is known about these drugs in children. A new micrococulture assay was developed for evaluation of drug susceptibility using single-passage HIV isolates cocultured with peripheral blood mononuclear cells from healthy donors. HIV isolates from children treated with zidovudine or ddI were evaluated to define the emergence of resistance to these antiretroviral agents. Four patients were treated with ddI and 3 with zidovudine for > 15 months. There was a > or = 20-fold decrease in susceptibility to ddI for sequential isolates of HIV recovered from 4 patients treated with ddI for 22-31 months and a 4- to 10-fold decrease in susceptibility to zidovudine in 3 patients. HIV isolates from 3 patients treated with ddI or zidovudine alone showed a minor amount of cross-resistance to the other antiretroviral agent. Results indicate the importance of monitoring antiretroviral drug susceptibility of HIV isolates when assessing clinical deterioration in children treated for > 1 year.

Sensitivity, specificity and predictive value of physical examination, culture and other laboratory studies in the diagnosis during early infancy of vertically acquired human immunodeficiency virus infection

The medical records of 142 infants referred for evaluation solely because they were born to human immunodeficiency virus (HIV)-infected mothers (i.e. not because of signs or symptoms suggesting HIV infection), were reviewed. The infection status of 85 of these infants has been determined; 17 (20%) have confirmed HIV infection and 68 have seroreverted to HIV and lack evidence of infection. During the first 6 months of life HIV culture had better sensitivity, specificity, positive predictive value and negative predictive value for diagnosis of HIV infection than did physical examination, serum immunoglobulin determination or HIV p24 antigen determination. Of the 16 HIV-infected infants who were available for evaluation during the first 6 months of life, all had at least one culture from blood positive for HIV. Two of 4 and 10 of 11 infants were culture-positive at birth and during the first 3 months of life, respectively. A positive HIV culture results was the earliest finding of infection in 15 infants; 10 of these infants concomitantly were found to have hyperimmunoglobulinemia (8 cases) and/or an abnormal physical examination (4 cases). One HIV-infected infant developed hyperimmunoglobulinemia G and A at age 3 months without other evidence of HIV infection until age 5 months when a positive HIV culture was noted. All HIV-infected infants had abnormal findings by physical examination, a positive HIV culture, and/or hyperimmunoglobulinemia by 3 months of age. Infants with normal physical examination and laboratory test results at 3 and/or 6 months of age invariably were HIV-uninfected.

Phosphorylation-associated conformation shift of anti-oncogene phosphoprotein p53 in concanavalin-A activated human T lymphocytes

A new radioimmunoassay for p53, employing an anti-peptide antibody directed against conserved Domain V, exhibited specificity for a relatively dephosphorylated form of p53. This form, correlated with the monoclonal antibody PAB421+ conformation, appeared transiently in the cytosol of cycloheximide-treated T cells undergoing activation by concanavalin-A/serum. Concurrently, there were decreased levels of p53 in the nucleus that correlated with increased phosphorylation of p53. After 90 min nuclear levels of p53 increased steadily above levels of unstimulated cells. Anti-p53 antibodies introduced into cells prior to stimulation enhanced cell proliferation in response to mitogens.

A protein kinase C-activating phorbol ester accelerates the T cell antigen receptor-stimulated phosphatidylinositol cycle in normal human CD4+ T cells

Ligation of the TCR on Jurkat T lymphoblastoid cells causes an 1,4,5-inositol trisphosphate-dependent rise in intracellular cytoplasmic calcium that is inhibited by PMA, a potent activator of protein kinase C. Consequently, protein kinase C is widely believed to mediate feedback inhibition of TCR-activated phospholipase C. We have now extended these studies to normal unblasted human CD4+ T lymphocytes, examining the PMA sensitivity of both the TCR complex-mediated release of total inositol-phosphates and the resynthesis of the parent phosphoinositides. In contrast to Jurkat, in which PMA inhibited release of 1,4,5-inositol trisphosphate by 60% and total inositolphosphates by 40% (50% inhibitory concentration, 5.6 nM), normal cells displayed a marked increase in anti-CD3-induced phosphatidylinositol (PI) cycling in the presence of PMA. Both total inositolphosphate release and PI resynthesis were maximally elevated (88% and 342%, respectively) by a PMA concentration that also optimally supported a subsequent proliferative response; the ED50 was at least 11.7-fold lower than that for the inhibitory effect of PMA on breakdown of total Jurkat PI. A PKC nonactivating phorbol ester had no effect. If anti-CD3 was replaced by the mitogenic lectin PHA, PI resynthesis was similarly up-regulated by PMA in these highly purified cells. The PMA up-regulatory phenomenon was not a simple consequence of cell blastogenesis, inasmuch as there was no early effect on the non-signaling-associated phosphatidylethanolamine compartment after CD3 stimulation. Thus, PKC activation appears to accelerate TCR-linked PI metabolism in normal Th cells, in contrast to the feedback inhibitor paradigm observed in Jurkat and other tumor cell systems.

A protein kinase C-activating phorbol ester accelerates the T cell antigen receptor-stimulated phosphatidylinositol cycle in normal human CD4+ T cells

Ligation of the TCR on Jurkat T lymphoblastoid cells causes an 1,4,5-inositol trisphosphate-dependent rise in intracellular cytoplasmic calcium that is inhibited by PMA, a potent activator of protein kinase C. Consequently, protein kinase C is widely believed to mediate feedback inhibition of TCR-activated phospholipase C. We have now extended these studies to normal unblasted human CD4+ T lymphocytes, examining the PMA sensitivity of both the TCR complex-mediated release of total inositol-phosphates and the resynthesis of the parent phosphoinositides. In contrast to Jurkat, in which PMA inhibited release of 1,4,5-inositol trisphosphate by 60% and total inositolphosphates by 40% (50% inhibitory concentration, 5.6 nM), normal cells displayed a marked increase in anti-CD3-induced phosphatidylinositol (PI) cycling in the presence of PMA. Both total inositolphosphate release and PI resynthesis were maximally elevated (88% and 342%, respectively) by a PMA concentration that also optimally supported a subsequent proliferative response; the ED50 was at least 11.7-fold lower than that for the inhibitory effect of PMA on breakdown of total Jurkat PI. A PKC nonactivating phorbol ester had no effect. If anti-CD3 was replaced by the mitogenic lectin PHA, PI resynthesis was similarly up-regulated by PMA in these highly purified cells. The PMA up-regulatory phenomenon was not a simple consequence of cell blastogenesis, inasmuch as there was no early effect on the non-signaling-associated phosphatidylethanolamine compartment after CD3 stimulation. Thus, PKC activation appears to accelerate TCR-linked PI metabolism in normal Th cells, in contrast to the feedback inhibitor paradigm observed in Jurkat and other tumor cell systems.

Impact of human immunodeficiency virus infection on women and infants

Infection with HIV is a problem of growing magnitude among women and children in the United States. During 1991, AIDS will be among the five leading causes of death for women of childbearing age. Over 80% of children with HIV have acquired the infection vertically, and AIDS is now a leading cause of death of children in many urban areas of the United States. Gender and age have important influences on the progression of HIV disease and on the occurrence of complicating illnesses. Zidovudine can slow HIV disease progression, and several regimens of prophylaxis are effective against P. carinii pneumonia, which is the leading cause of death among adults and children with AIDS. Intravenous immunoglobulin may be effective for prevention of serious infections in some children with symptomatic HIV infection. Ultimately, prevention of HIV infection among women and children depends on targeted education and, possibly, the development of medical strategies for interruption of vertical transmission.

High-level expression of functional platelet-activating factor receptors on a human B lymphoblastoid cell line

Binding of platelet-activating factor (PAF) was characterized in a human b lymphoblastoid cell line, ASK.0. [3H]PAF binding to these cells was time-dependent, reaching equilibrium at 60 minutes, and saturable. Scatchard analyses of saturation binding experiments revealed a single class of PAF binding sites (108,000 +/- 17,000 per cell) with a KD of 2.16 +/- 0.41 nM. That the binding sites were specific for PAF was demonstrated by competition studies. PAF was shown to increase the intracellular calcium concentrations of ASK.0 cells in a dose-dependent manner with an EC50 of 7 nM. We have, therefore, identified a B cell line expressing large numbers of functional PAF receptors.

Cyclic AMP-mediated modulation of immunoglobulin production in B cells by prostaglandin E1

We had previously demonstrated in a transformed human B cell line, LA350, the existence of an inverse relationship between cyclic adenosine monophosphate (cAMP) content and immunoglobulin secretion using the cAMP-elevating agents such as cholera toxin and forskolin. In this paper we report that cAMP acting as a second messenger for prostaglandin exerts a similar effect on the antibody response of B lymphocytes. Incubation of the cells with PGE1 in the presence of the phosphodiesterase inhibitor isobutylmethylxanthine (IBMX) produced a concentration- and time-dependent elevation of intracellular cAMP. Significant increases of cAMP production were observed at physiologically relevant levels of PGE1 (10(-7) and 10(-8) M). Immunoglobulin production, whether measured as the total number of immunoglobulin-secreting cells by a reverse hemolytic plaque assay or as specific immunoglobulin production (IgM) by an enzyme-linked immunoadsorbent assay, was suppressed in a dose-dependent fashion by the presence of IBMX. This suppression of immunoglobulin production was significantly enhanced by the presence of PGE1. Phorbol myristate acetate-induced IgM production was also inhibited by the presence of PGE1. These results imply that prostaglandins regulate B cell activation and immunoglobulin production by signal transduction mechanisms involving cyclic nucleotides.

Phorbol ester plus calcium ionophore induces release of arachidonic acid from membrane phospholipids of a human B cell line

Binding of LA350, a lymphoblastoid human B cell line, by phorbol myristate acetate (PMA) plus a calcium ionophore, either ionomycin or A23187, produced unique alterations in the release of arachidonic acid (AA) from cellular phospholipids. After equilibrium labeling of cells with radioactive fatty acids, [14C]AA demonstrated a selective enhanced release from the cells in response to the binding of PMA plus calcium ionophore as compared to the release of [14C]stearic acid (STE), [3H]oleic acid (OLE) and [3H]palmitic acid (PAL). The major phospholipid sources of the released [14C]AA were shown to be phosphatidylcholine, phosphatidylethanolamine, and phosphatidylinositol. The participation of protein kinase C (PKC) in the enhanced synergistic release of [14C]AA was demonstrated by the inhibition of the release by the PKC inhibitor, staurosporine. Approximately 2-6% of the labeled AA liberated was converted to 5-hydroxyeicosatetraenoic acid by an endogenous 5-lipoxygenase. Therefore during cell activation the B cell is capable of liberating AA via a PKC-dependent mechanism, implicating AA and/or its metabolites in signal transduction.

Monoclonal anti-T cell (T12) antibody treatment of graft-versus-host disease in severe combined immunodeficiency: targeting of antibody and activation of complement on CD8+ cytotoxic T cell surfaces

We report a 6-month-old male child with severe combined immunodeficiency who received an unirradiated blood transfusion and developed acute, severe graft-versus-host disease (GVHD), for which he received monoclonal anti-T cell (anti-T12) antibody treatment. The GVHD was manifested by a confluent maculopapular rash and increased liver function tests and was documented by skin biopsy. Separation of peripheral blood mononuclear cells forming rosettes with sheep red blood cells revealed engrafted T cells having the nonrelated HLA type of the blood donor. The patient was treated with intravenous monoclonal anti-T12 in a dose of 0.3 mg/kg/day for 5 days. An in vivo effect of the anti-T12 was suggested by clinical improvement of his skin rash and return of the liver transaminases to the normal range. Moreover, human complement components, activated C3 and C4, were detected by fluorescence microscopy on the surfaces of the engrafted CD8+ lymphocytes on the skin biopsy specimens. Also, with a biotin-avadin assay, the presence of the anti-T12 was detected on these same cells. These studies document not only the in vivo targeting of monoclonal anti-T12 antibody to cytotoxic T cells producing GVHD but also the activation of complement on these cells.

Platelet-activating factor induces phospholipid turnover, calcium flux, arachidonic acid liberation, eicosanoid generation, and oncogene expression in a human B cell line

Platelet-activating factor is a potent mediator of the inflammatory response. Studies of the actions of platelet-activating factor have centered mainly around neutrophils, monocytes, and platelets. In this report we begin to uncover the influence of platelet-activating factor on B lymphocytes. Employing the EBV-transformed human B cell line SKW6.4, we demonstrate that platelet-activating factor significantly alters membrane phospholipid metabolism indicated by the incorporation of 32P into phosphatidylcholine, phosphatidylinositol, and phosphatidic acid but not significantly into phosphatidylethanolamine at concentrations ranging from 10(-9) to 10(-6) M. The inactive precursor, lyso-platelet-activating factor, at a concentration as high as 10(-7) M had no effect on any of the membrane phospholipids. We also show that platelet-activating factor from 10(-12) to 10(-6) M induced rapid and significant elevation in intracellular calcium levels, whereas lyso-platelet-activating factor was again ineffective. We further demonstrate the impact of platelet-activating factor binding to B cells by measuring platelet-activating factor induced arachidonic acid release and 5-hydroxyeicosatetraenoic acid production. Moreover, platelet-activating factor was capable of inducing transcription of the nuclear proto-oncogenes c-fos and c-jun. Finally we explored the possible role of 5-hydroxyeicosatetraenoic acid as a regulator of arachidonic acid liberation demonstrating that endogenous 5-lipoxygenase activity modulates platelet-activating factor induced arachidonic acid release perhaps acting at the level of phospholipase A2. In summary, platelet-activating factor is shown here to have a direct and profound effect on a pure B cell line.

Platelet-activating factor induces phospholipid turnover, calcium flux, arachidonic acid liberation, eicosanoid generation, and oncogene expression in a human B cell line

Platelet-activating factor is a potent mediator of the inflammatory response. Studies of the actions of platelet-activating factor have centered mainly around neutrophils, monocytes, and platelets. In this report we begin to uncover the influence of platelet-activating factor on B lymphocytes. Employing the EBV-transformed human B cell line SKW6.4, we demonstrate that platelet-activating factor significantly alters membrane phospholipid metabolism indicated by the incorporation of 32P into phosphatidylcholine, phosphatidylinositol, and phosphatidic acid but not significantly into phosphatidylethanolamine at concentrations ranging from 10(-9) to 10(-6) M. The inactive precursor, lyso-platelet-activating factor, at a concentration as high as 10(-7) M had no effect on any of the membrane phospholipids. We also show that platelet-activating factor from 10(-12) to 10(-6) M induced rapid and significant elevation in intracellular calcium levels, whereas lyso-platelet-activating factor was again ineffective. We further demonstrate the impact of platelet-activating factor binding to B cells by measuring platelet-activating factor induced arachidonic acid release and 5-hydroxyeicosatetraenoic acid production. Moreover, platelet-activating factor was capable of inducing transcription of the nuclear proto-oncogenes c-fos and c-jun. Finally we explored the possible role of 5-hydroxyeicosatetraenoic acid as a regulator of arachidonic acid liberation demonstrating that endogenous 5-lipoxygenase activity modulates platelet-activating factor induced arachidonic acid release perhaps acting at the level of phospholipase A2. In summary, platelet-activating factor is shown here to have a direct and profound effect on a pure B cell line.

Evaluation and management of B and T cell abnormalities

Congenital deficiencies that involve the lymphocyte system are complex and represent abnormalities in genetic control or gestational development. Only the more common prototypes of these diseases will be discussed. Diseases of the B cell system presented include X-linked agammaglobulinemia, selective IgA deficiency, IgG subclass deficiency, and common variable immunodeficiency. T cell defects discussed are Di-George syndrome and severe combined immunodeficiency. Also mentioned briefly are HIV infection and the increasing problem of AIDS. Diagnostic evaluation and general principles of treatment of these diseases are considered.

Enhancement of cyclic AMP metabolism in a B cell line by protein kinase C

In a human B cell line in which we previously demonstrated an inverse relationship between cyclic adenosine monophosphate (cAMP) content and immunoglobulin secretion, the phorbol ester, phorbol myristate acetate, (PMA), was shown to augment the cAMP elevating ability of cholera toxin (CT), suggesting a regulatory linkage between the two transmembrane signaling pathways, cAMP and phospholipid (J. Immunol. 141, 1678-1686, 1988). We now extend these studies and provide additional evidence that activated protein kinase C, a principal product of the activation of the hydrolytic phospholipid pathway, plays a direct role in the augmentation of cAMP levels in cells stimulated by diverse cAMP-elevating ligands. Prostaglandin E1 (PGE1), forskolin (FSK) and CT, all of which demonstrated a concentration and time-dependent elevation of intracellular cAMP, produced even greater (up to twofold) elevations of cAMP in the presence of PMA or the diacylglycerol analogs, 1,2-dioctanoylglycerol (DiC8), and 1-oleoyl-2-acetylglycerol (OAG). In the absence of CT, PGE1, or FSK, these protein kinase C activators produced only small increases in cAMP content of the cells. Several tests of protein kinase C specificity in these PMA-, DiC8-, and OAG-induced augmentations were made: (i) only phorbol esters known to activate protein kinase C worked, (ii) PMA augmentation was abolished by down-regulation of protein kinase C, (iii) Staurosporine (a known inhibitor of protein kinase C) selectively inhibited the effects of PMA on cAMP generation and on immunoglobulin secretion in the LA350 cell line.

Evidence for 5-lipoxygenase activity in human B cell lines. A possible role for arachidonic acid metabolites during B cell signal transduction

Ligand binding to B lymphocytes via membrane Ig initiates a cascade of events beginning with the hydrolysis of phosphatidylinositol 4,5-bisphosphate into diacylglycerol and inositol 1,4,5-trisphosphate. Subsequent to the activation of protein kinase C and the induction of a rise in intracellular calcium by diacylglycerol and inositol 1,4,5-trisphosphate, there is gene transcription and eventually cellular activation. By mimicking the initial event of B cell activation with phorbol ester and calcium ionophore one can begin to identify the many mediators used in signaling between the membrane and the nucleus. We have examined the effect of calcium on arachidonic acid (AA) metabolism in several EBV-transformed human B cell lines. The cells were labelled with [3H]AA and stimulated with the calcium ionophore A23187. Analysis of the supernatant by reversed-phase HPLC demonstrated a dose-dependent release of an AA metabolite that coeluted with authentic 5-hydroxyeicosatetraenoic acid (5-HETE). In addition, the AA metabolite coeluted with standard 5-HETE under straight-phase chromatography. Further analysis by RIA confirmed the identification of 5-HETE and revealed an additional metabolite, 5-HETE lactone (5-HL). 5-HL is the intramolecular ester of 5-HETE generated in the presence of acid. We were unable to convert [3H] 5-HETE into 5-HL during sample preparation unless cells were present, suggesting that the 5-HL, is of cellular origin. These results suggest that the AA metabolites 5-HETE and its intramolecular ester 5-HL may play a role in B cell activation because they are produced subsequent to a rise in intracellular Ca2+, an event that occurs during cross-linking of membrane Ig.

Evidence for 5-lipoxygenase activity in human B cell lines. A possible role for arachidonic acid metabolites during B cell signal transduction

Ligand binding to B lymphocytes via membrane Ig initiates a cascade of events beginning with the hydrolysis of phosphatidylinositol 4,5-bisphosphate into diacylglycerol and inositol 1,4,5-trisphosphate. Subsequent to the activation of protein kinase C and the induction of a rise in intracellular calcium by diacylglycerol and inositol 1,4,5-trisphosphate, there is gene transcription and eventually cellular activation. By mimicking the initial event of B cell activation with phorbol ester and calcium ionophore one can begin to identify the many mediators used in signaling between the membrane and the nucleus. We have examined the effect of calcium on arachidonic acid (AA) metabolism in several EBV-transformed human B cell lines. The cells were labelled with [3H]AA and stimulated with the calcium ionophore A23187. Analysis of the supernatant by reversed-phase HPLC demonstrated a dose-dependent release of an AA metabolite that coeluted with authentic 5-hydroxyeicosatetraenoic acid (5-HETE). In addition, the AA metabolite coeluted with standard 5-HETE under straight-phase chromatography. Further analysis by RIA confirmed the identification of 5-HETE and revealed an additional metabolite, 5-HETE lactone (5-HL). 5-HL is the intramolecular ester of 5-HETE generated in the presence of acid. We were unable to convert [3H] 5-HETE into 5-HL during sample preparation unless cells were present, suggesting that the 5-HL, is of cellular origin. These results suggest that the AA metabolites 5-HETE and its intramolecular ester 5-HL may play a role in B cell activation because they are produced subsequent to a rise in intracellular Ca2+, an event that occurs during cross-linking of membrane Ig.

Evidence for a platelet-activating factor receptor on human lymphoblastoid B cells: activation of the phosphatidylinositol cycle and induction of calcium mobilization

In this report we demonstrate evidence which strongly suggests that a receptor for platelet-activating factor (PAF) exists on a lymphoblastoid B cell line, LA350. PAF ranging in concentration from 10(-6)-10(-9)M initiated the incorporation of 32P into phosphatidic acid (PA) and phosphatidylinositol (PI) with no change in phosphatidylethanolamine (PE) and phosphatidylcholine (PC) over baseline. Lyso-PAF, the inactive precursor, at 10(-7)M had no effect on membrane phospholipid metabolism. In addition, PAF from 10(-6)-10(-8)M when added to Fura-2 containing B cells induced a rapid and significant rise of calcium within the cell, with lyso-PAF having no effect. These data suggest that PAF binds to a receptor on B cells and induces the hydrolysis of PI and a subsequent increase of intracellular calcium.