Development of an expert system knowledge base: a novel approach to promote guideline congruent asthma care

Existing guidelines for the clinical management of asthma provide a good framework for such tasks as diagnosing asthma, determining severity, and prescribing pharmacological treatment. Guidance is less explicit, however, about establishing a patient-provider partnership and overcoming barriers to asthma management by patients in a way that can be easily adopted in clinical practice. We report herein the first developmental phase of the "Stop Asthma" expert system. We describe the establishment of a knowledge base related to both the clinical management of asthma and the enhancement of patient and family self-management (including environmental management). The resultant knowledge base comprises 142 multilayered decision rules that describe clinical and behavioral management in three domains: 1) determination of asthma severity and control; 2) pharmacotherapy, including prescription of medicine for chronic maintenance, acute exacerbation, exercise pretreatment, and rhinitis relief; and 3) patient self-management, including the process of intervening to facilitate the patient's asthma medication management, environmental control, and well-visit scheduling. The knowledge base provides a systematic and accessible approach for intervening with family asthma-related behaviors.

Impact of a computer-assisted education program on factors related to asthma self-management behavior

OBJECTIVE

To evaluate Watch, Discover, Think and Act (WDTA), a theory-based application of CD-ROM educational technology for pediatric asthma self-management education.

DESIGN

A prospective pretest posttest randomized intervention trial was used to assess the motivational appeal of the computer-assisted instructional program and evaluate the impact of the program in eliciting change in knowledge, self-efficacy, and attributions of children with asthma. Subjects were recruited from large urban asthma clinics, community clinics, and schools. Seventy-six children 9 to 13 years old were recruited for the evaluation.

RESULTS

Repeated-measures analysis of covariance showed that knowledge scores increased significantly for both groups, but no between-group differences were found (P: = 0.55); children using the program scored significantly higher (P: < 0.01) on questions about steps of self-regulation, prevention strategies, and treatment strategies. These children also demonstrated greater self-efficacy (P: < 0.05) and more efficacy building attribution classification of asthma self-management behaviors (P: < 0.05) than those children who did not use the program.

CONCLUSION

The WDTA is an intrinsically motivating educational program that has the ability to effect determinants of asthma self-management behavior in 9- to 13-year-old children with asthma. This, coupled with its reported effectiveness in enhancing patient outcomes in clinical settings, indicates that this program has application in pediatric asthma education.

Recombinant human gamma interferon in human immunodeficiency virus-infected children: safety, CD4(+)-lymphocyte count, viral load, and neutrophil function (AIDS Clinical Trials Group Protocol 211)

Nineteen children with human immunodeficiency virus (HIV) infection were treated with recombinant human gamma interferon (rIFN-gamma) (50 microg/m2 subcutaneously three times each week during weeks 1 through 12 and 100 microg/m2 subcutaneously three times each week during weeks 13 through 24) in a phase I/II clinical trial. All children continued to receive previously prescribed therapy with oral zidovudine or didanosine. Children were assessed clinically and with laboratory studies during 24 weeks of study treatment and for 12 weeks after completion of rIFN-gamma therapy. In general, rIFN-gamma therapy was well tolerated. There were two clinical or laboratory adverse events thought to be possibly or probably study drug associated. One child developed acute pancreatitis; another child developed granulocytopenia. Median CD4(+)-lymphocyte counts and plasma HIV RNA concentrations did not change significantly during therapy. In vitro neutrophil bactericidal activity against Staphylococcus aureus and superoxide production were not significantly affected by rIFN-gamma therapy. We conclude that rIFN-gamma therapy in HIV-infected children receiving single-agent antiretroviral therapy is safe and does not produce consistent changes in CD4(+)-lymphocyte count, plasma HIV RNA concentration, or in vitro neutrophil function.

Objective measures of allergic disease in children with human immunodeficiency virus infection

BACKGROUND

Available information suggests that IgE levels are elevated in adults infected with human immunodeficiency virus (HIV), and that increased IgE levels correlate with allergic disease, with decreased CD4 counts, and with a poor prognosis. Data with respect to these factors in children are scant.

OBJECTIVE

We investigated whether serum IgE levels are elevated in children with HIV and, if so, whether the serum IgE level correlates with the degree of immunodeficiency and/or objective indicators of allergic disease.

METHODS

Serum IgE levels, CD4 counts, absolute eosinophil counts, and immediate hypersensitivity skin test (IHST) results were collected from 43 children with symptomatic HIV infection (mean age 7.2 years). Associations between serum IgE levels, CD4 counts, and eosinophil counts were investigated by multiple stepwise linear regression analysis. Data were stratified according to IHST positivity, and analysis of variance was used to compare mean values for age, CD4 counts, IgE levels, and eosinophil counts between the two groups.

RESULTS

Serum IgE values were elevated more than 2 SDs above control age-matched mean values in 17 of 43 patients (40%). IHST results were positive in 12 of 43 patients (28%). CD4 counts were less than 200/mm3 in 17 of 43 patients (40%). Stepwise linear regression failed to demonstrate any correlation between serum IgE levels and either CD4 or eosinophil counts. With data divided into two groups according to IHST results (positive vs negative), analysis of variance failed to reveal significant differences between means for patient age, CD4 counts, IgE levels, or eosinophil counts.

CONCLUSIONS

Our findings confirm that serum IgE levels are increased in children infected with HIV, just as in adults. However, an elevated serum IgE level did not correlate with allergic disease as measured by IHST results and eosinophil counts, nor with the degree of immune dysfunction as approximated by CD4 counts. The mechanism and significance of elevated serum IgE levels remain unclear in children with HIV, and warrant further investigation.

The surgical implications of chronic granulomatous disease

BACKGROUND

Chronic granulomatous disease (CGD) of childhood is a rare congenital abnormality of the phagocyte NADPH oxidase system. Affected neutrophils and macrophages have an ineffective respiratory burst and cannot destroy certain phagocytized bacteria and fungi. CGD patients usually present with recurrent pyogenic and fungal infections. Catalase-positive bacteria are frequently involved, since they metabolize the hydrogen peroxide they produce, making it unavailable for augmentation of microbicidal activity in CGD neutrophils. Afflicted patients also have a tendency to form granulomas, which can lead to obstruction of the gastrointestinal and genitourinary tracts.

METHODS

Charts of 10 patients with CGD were reviewed for age at diagnosis, surgical procedures, complications of these procedures, and medical treatment.

RESULTS

Eight of the 10 children were male. The average age at first presentation was 18 months (range 2 days to 9.8 years). Each child developed a mean of 9.9 infections and an average of 1.4 infections per year. All required surgical procedures, with an average of 2.9 procedures each. Five children had operative procedures for infections that preceded the diagnosis of CGD. The procedures performed most frequently were incision and drainage of soft-tissue abcesses (7) or perirectal abscess (3), thoracentesis (3), and bronchoscopy (3). Three children had poor wound healing following surgery. Two developed partial gastric outlet obstruction which resolved with antibiotic therapy. One developed granulomatous cystitis with obstruction which responded to antibiotics.

CONCLUSIONS

Since patients with undiagnosed CGD may present with surgical problems, surgeons need to be familiar with this condition. The diagnosis should be suspected in children who have recurrent or unusual infections or unexplained problems with wound healing.

Ascorbic acid enhances iron-induced ferritin translation in human leukemia and hepatoma cells

Ascorbate is an important cofactor in many cellular metabolic reactions and is intimately linked to iron homeostasis. Continuously cultured cells are ascorbate deficient due to the lability of the vitamin in solution and to the fact that daily supplementation of media with ascorbate is unusual. We found that ascorbate repletion alone did not alter ferritin synthesis. However, ascorbate-replete human hepatoma cells, Hep3B and HepG2, as well as K562 human leukemia cells achieved a substantially higher cellular ferritin content in response to a challenge with iron than did their ascorbate-deficient counterparts grown under standard culture conditions. Most of the elevation in ferritin content was due to an increase in de novo ferritin synthesis of greater than 50-fold, as shown by in vivo labeling with [35S]methionine and immunoprecipitation. RNA-blot analysis showed only minor changes in steady state levels of ferritin mRNA, suggesting that ascorbate enhances iron-induced ferritin synthesis primarily by post-transcriptional events. Transient gene expression experiments using chloramphenicol acetyltransferase reporter gene constructs showed that the ascorbate effect on ferritin translation is not mediated through the stem-loop near the translational start site that transduces ferritin synthesis in response to cytokines. The data suggest that ascorbate possibly modifies the action of the iron-responsive element on ferritin translation, although more precise structure-function studies are needed to clarify this issue. These data demonstrate a novel role of ascorbate as a signaling molecule in post-transcriptional gene regulation. The mechanism by which ascorbate modulates cellular iron metabolism is complex and requires additional detailed investigation.

IL-4 inhibits superoxide production by human mononuclear phagocytes

The activation of mononuclear phagocytes (M phi) and their generation of oxidative products is influenced by various cytokines as well as by normal maturational changes. We examined the effects of IL-4 on superoxide (O2-) production (cytochrome c reduction) by cultured M phi and the modulation of these effects by IFN-gamma and IL-1. Incubation of IL-4 (200 U/ml) with M phi inhibited M phi PMA (100 ng/ml)-stimulated O2-. production by 23% at 24 h, 34% at 48 h, and 70 to 85% at 72 to 96 h. IL-4 similarly inhibited M phi O2-. production in response to zymosan. IL-4 did not affect M phi viability, adherence to microtiter plates, or ability to phagocytose boiled yeast. In comparison with M phi, neutrophil O2-. production was not inhibited after 4 to 20 h incubation with IL-4. When IL-4 was washed out as early as 1 h after the initiation of M phi culture, significant inhibition of O2-. production was observed 4 days later. Sequential addition of either IL-4 or IFN-gamma to cultures demonstrated reciprocal cytokine effects on M phi; IL-4 partially inhibited O2-. production by M phi previously treated with rIFN-gamma whereas rIFN-gamma partially augmented O2-. production by M phi previously treated with IL-4. Because IL-4 has been reported to inhibit IL-1 production, add-back experiments were performed; addition of IL-1 only partly reconstituted O2-. production in IL-4-treated cells. Further characterization showed that although M phi protein synthesis was enhanced by both rIFN-gamma and IL-4 treatment, acid phosphatase, a marker of maturation to the macrophage phenotype, was markedly increased at an earlier time point in IL-4-treated M phi, and correlated with a decline in O2-. production. The ability of IL-4 to suppress M phi O2-. production implicates IL-4 as an important regulator of this aspect of the inflammatory response.

IL-4 inhibits superoxide production by human mononuclear phagocytes

The activation of mononuclear phagocytes (M phi) and their generation of oxidative products is influenced by various cytokines as well as by normal maturational changes. We examined the effects of IL-4 on superoxide (O2-) production (cytochrome c reduction) by cultured M phi and the modulation of these effects by IFN-gamma and IL-1. Incubation of IL-4 (200 U/ml) with M phi inhibited M phi PMA (100 ng/ml)-stimulated O2-. production by 23% at 24 h, 34% at 48 h, and 70 to 85% at 72 to 96 h. IL-4 similarly inhibited M phi O2-. production in response to zymosan. IL-4 did not affect M phi viability, adherence to microtiter plates, or ability to phagocytose boiled yeast. In comparison with M phi, neutrophil O2-. production was not inhibited after 4 to 20 h incubation with IL-4. When IL-4 was washed out as early as 1 h after the initiation of M phi culture, significant inhibition of O2-. production was observed 4 days later. Sequential addition of either IL-4 or IFN-gamma to cultures demonstrated reciprocal cytokine effects on M phi; IL-4 partially inhibited O2-. production by M phi previously treated with rIFN-gamma whereas rIFN-gamma partially augmented O2-. production by M phi previously treated with IL-4. Because IL-4 has been reported to inhibit IL-1 production, add-back experiments were performed; addition of IL-1 only partly reconstituted O2-. production in IL-4-treated cells. Further characterization showed that although M phi protein synthesis was enhanced by both rIFN-gamma and IL-4 treatment, acid phosphatase, a marker of maturation to the macrophage phenotype, was markedly increased at an earlier time point in IL-4-treated M phi, and correlated with a decline in O2-. production. The ability of IL-4 to suppress M phi O2-. production implicates IL-4 as an important regulator of this aspect of the inflammatory response.

Regulation of immunoglobulin production in hyperimmunoglobulin E recurrent-infection syndrome by interferon gamma

The hyperimmunoglobulin E recurrent-infection (Job) syndrome (HIE) is a congenital disorder characterized by high serum IgE, chronic eczematoid dermatitis, and recurrent infections. We examined the effect of interferon gamma (IFN-gamma) on excessive IgE production in HIE patients. Spontaneous in vitro production of IgE by peripheral blood mononuclear cells from HIE patients was elevated compared to normal individuals and correlated with serum IgE. In 9 of 13 patients, IgE production by peripheral blood mononuclear cells was inhibited by 50% by IFN-gamma at 100-1000 units/ml, whereas inhibition by IFN-gamma at 10(4) units/ml ranged from 67 to 93% for these 9 patients. IFN-gamma also inhibited IgG1, IgG3, and IgG4 production by B lymphocytes without inhibiting IgG2 production. IFN-gamma was administered subcutaneously to 5 HIE patients. After 2 weeks of treatment with IFN-gamma (0.05 mg/m2) at three doses per week given on alternate days, peripheral blood mononuclear cells from all 5 HIE patients decreased spontaneous in vitro IgE production (27-62% decrease) with no change in IgG and IgM. One patient had a 58% decrease in serum IgE and another patient had a 50% decrease in serum IgE after the IFN-gamma was increased to 0.1 mg/m2 for three doses per week for a month. In both patients, serum IgE returned to pre-IFN-gamma-challenge levels 1-3 months after completion of treatment, and in vivo IFN-gamma did not affect serum IgG and IgM, although serum IgG4 decreased with changes in serum IgE. Our studies demonstrate that IFN-gamma can regulate production of IgE and some IgG subclasses in humans.

Cellular requirements for induction of human primary proliferative responses to trinitrophenyl-modified cells

Cellular requirements for induction of primary proliferative responses by human T cells to trinitrophenylated autologous stimulators have been characterized. Substantial proliferative responses were observed with each of the Ia+ stimulator populations tested. Nevertheless, major differences in the hapten specificity of such responses were observed. Thus purified macrophages/monocytes (M phi) when TNP-modified induced responses that were relatively modest in absolute magnitude, but were highly hapten specific. This reflected the very limited capacity of purified M phi to induce proliferation when unmodified, i.e., an autologous mixed leukocyte response (AMLR). In contrast, unmodified M phi-depleted B plus null cells were potent stimulators of AMLR, but hapten modification did not significantly enhance the responses induced by these cells. Moreover, when M phi were added to B plus null cell stimulators AMLR responses were reduced and, with TNP-modified stimulators, hapten-specific responses were restored. The data thus suggest that M phi may have important roles in induction of primary T cell responses to conventional antigens but function largely as regulators rather than stimulators of AMLR. Finally, we have introduced a novel antigen-presenting cell population, the irradiated Ia+ TNP-specific cloned T cell. The possibility that such cells may utilize autostimulatory positive feedback circuits for activation of naive T cells and in interactions between subpopulations of hapten-reactive T cells is discussed.

Cellular requirements for induction of human primary proliferative responses to trinitrophenyl-modified cells

Cellular requirements for induction of primary proliferative responses by human T cells to trinitrophenylated autologous stimulators have been characterized. Substantial proliferative responses were observed with each of the Ia+ stimulator populations tested. Nevertheless, major differences in the hapten specificity of such responses were observed. Thus purified macrophages/monocytes (M phi) when TNP-modified induced responses that were relatively modest in absolute magnitude, but were highly hapten specific. This reflected the very limited capacity of purified M phi to induce proliferation when unmodified, i.e., an autologous mixed leukocyte response (AMLR). In contrast, unmodified M phi-depleted B plus null cells were potent stimulators of AMLR, but hapten modification did not significantly enhance the responses induced by these cells. Moreover, when M phi were added to B plus null cell stimulators AMLR responses were reduced and, with TNP-modified stimulators, hapten-specific responses were restored. The data thus suggest that M phi may have important roles in induction of primary T cell responses to conventional antigens but function largely as regulators rather than stimulators of AMLR. Finally, we have introduced a novel antigen-presenting cell population, the irradiated Ia+ TNP-specific cloned T cell. The possibility that such cells may utilize autostimulatory positive feedback circuits for activation of naive T cells and in interactions between subpopulations of hapten-reactive T cells is discussed.

Antigen presentation to human T lymphocytes. II. Requirements for Mac-120+ macrophages and responsiveness to interleukin 2

To investigate mechanisms by which antigen, macrophages, and interleukin 2 (IL2) participate in the induction of secondary T-cell proliferative responses, trinitrophenyl (TNP) was presented in three distinct modes: (i) TNP-modified peripheral blood mononuclear cells (TNP-PBMC), (ii) TNP-PBMC cell sonicates, and (iii) TNP-ovalbumin (TNP-OVA). Stimulators were depleted of Mac-120+ macrophages using Mac-120 monoclonal antibody plus complement. TNP-Mac-120 macrophages stimulated primed T cells nearly as well as TNP-unfractionated macrophages (which were about 40% Mac-120+). In contrast, although greater than 70% DR+, Mac-120- macrophages plus either TNP-OVA or TNP-PBMC sonicate elicited minimal responses compared to unfractionated macrophages plus antigen. After 21-28 days of in vitro priming, macrophage-depleted T cells were not stimulated to proliferate by either IL2 alone or sonicates alone. IL2 plus TNP-PBMC sonicates, however, stimulated significant proliferation. Furthermore, this response was considerably greater than that to IL2 plus either TNP-T cell sonicates or TNP-mouse spleen sonicates. Thus, the Mac-120+ macrophage population may have an important antigen-presenting and/or accessory function in the stimulation of primed T cells by soluble or particulate antigen, although it is unnecessary for responses to intact TNP-Ia+ PBMC. In addition, the data suggest that Ia+ sonicates alone may suffice for induction of IL2 responsiveness, but not for endogenous IL2 production and subsequent proliferation by primed T cells.

Angioimmunoblastic lymphadenopathy with hypogammaglobulinemia. Possible role of monocyte suppression

A patient wit angioimmunoblastic lymphadenopathy had low serum immunoglobulin values and no antibodies to injected immunogens. This occurred despite the proliferation of polyclonal B cells. T cells were deficient in number and in lymphoproliferative responses, but their helper and suppressor functions were maintained. Ia-antigen bearing leukocytes from the patient stimulated poorly in mixed leukocyte culture. In vitro immunoglobulin synthesis by mononuclear leukocytes form the patient was severely impaired. These leukocytes actively suppressed immunoglobulin synthesis by normal cells from healthy subjects in co-culture. The responsible cell had characteristics of a monocyte. The suppression was selective for humoral immunity and was manifest despite normal numbers of monocytes. It appears that heterogeneous immunoregulatory abnormalities can underlie the syndrome of angioimmunoblastic lymphadenopathy. Furthermore, monocyte suppressor abnormalities may be implicated in clinical disease phenomena.

Antigen presentation to human T lymphocytes. I. Different requirements for stimulation by hapten-modified cells vs. cell sonicates

We have investigated the cellular and antigenic requirements for incubation of secondary proliferative responses by human T lymphocytes. Two distinct properties of antigen-presenting peripheral blood mononuclear cells were studied: (a) the ability for appropriate cell surface constituents to construct an immunogenic moiety, and (b) the ability to present similar antigenic determinants when they are not covalently bound. Only Ia+ hapten-modified cells were effective stimulators. In contrast, both Ia+ and Ia- cell sonicates could stimulate secondary proliferative responses, but only in the presence of an accessory cell. This accessory cell was present in Ia+ macrophage, but not in Ia+ non-T lymphocyte, preparations. In contrast, macrophages or soluble factors produced by macrophages were not required for primed T cells to undergo hapten-specific proliferation in response to hapten-modified Ia+ stimulator cells. Thus, although all Ia+ cells tested can stimulate primed cells to proliferate, not all Ia+ cells can function as accessory cells for responses to sonicates. This may reflect the unique ability of a subpopulation(s) of Ia+ cells to bind or process sonicates or soluble antigens for appropriate recognition by primed T cells.

Role of Ia-positive cells in induction of secondary human immune responses to haptens in vitro

We have described techniques for induction of primary and secondary human immune responses in vitro to lymphoid cells modified with trinitrophenyl, dinitrophenyl, and fluorescein isothiocyanate. Optimal secondary proliferative responses required the presentation of hapten on stimulator cells that shared HLA-D region determinants with the responder cell and/or the original stimulator cell. In contrast, hapten-specific cytotoxic responses assessed on modified allogeneic targets with no detected HLA homology with the responder were comparable in magnitude to those detected on modified autologous targets. Furthermore, secondary proliferative, but not cytotoxic, responses required presentation of Ia+ stimulator populations. Modified B cells, surface-immunoglobulin-negative, non T cells (null-cells), and Ia+ activated T cells all induced proliferative responses at least as effectively as equal numbers of hapten-conjugated macrophage/monocytes. Conversely, Ia(-) null cells and macrophages were entirely unable to stimulate. The data thus suggest that for proliferative responses, primed human T cells respond to modified lymphoid cells only when hapten is recognized in the context of Ia molecules.

Recognition of hapten-modified cells in vitro by human T-lymphocytes

Clearer definition of the recognitive structures of human T lymphocytes for antigens will be required to elucidate the molecular basis of diseases and immunological responses induced or regulated by normal or abnormal T-cell function. For this purpose we have investigated the cellular requirements for immune responses in vitro to trinitrophenyl-conjugated peripheral blood mononuclear cells. The responding cell was characterized as a T cell on the basis of rosetting with sheep erythrocytes. T-cell recognition of hapten in proliferative responses depended upon presentation of antigen in an appropriate stimulator-cell context. Neither autologous hapten-modified erythrocytes nor T cells restimulated responses of in vitro-primed lymphocytes. Moreover, hapten-conjugated non-T cells were more effective than modified unfractionated cells in restimulating proliferative responses. Both macrophages and non-T lymphocytes effectively restimulated hapten-conjugate responses.Cell-mixing experiments indicated that the failure of haptenated T cells to stimulate proliferative responses was not because of a lack of fresh macrophages; these experiments suggested instead that T cells do not express appropriate structures necessary to present haptenic determinants in an immunogenic form. Hapten-modified T cells, however, were capable of inducing primed lymphocytes to become efficient cytotoxic effector cells, indicating that T-cell recognitive units for stimulation of proliferative and cytotoxic responses are different. These data support the concept that for induction of proliferative responses, human T cells recognize conventional antigens in association with HLA-D-region-encoded Ia-like molecules.