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Biomedical subjects

Kenneth S Knox

Publications and source records attributed to Kenneth S Knox.

At least 19 recordsLinked to original sources
PubMed2006

Functional impairment of CD4 T cells despite normalization of T cell number in HIV.

Using an in vitro model, we demonstrate that when CD4 T cells from HIV infected subjects are enriched from total blood lymphocytes the immune response to antigen is augmented. However, augmentation of this response is confined to HIV infected subjects with relatively preserved CD4 T cell counts. Enriching for CD4 T cells had no effect on antigen responses in patients with low CD4 lymphocyte counts. These findings support the concept that CD4 T cells in late stage HIV have inherent qualitative defects.

Adult↗
PubMed2006

Diagnosis of pulmonary histoplasmosis and blastomycosis by detection of antigen in bronchoalveolar lavage fluid using an improved second-generation enzyme-linked immunoassay.

Antigen detection is a useful adjunct for the diagnosis of histoplasmosis. The purpose of this study was to evaluate antigen detection in bronchoalveolar lavage (BAL) fluid using an improved second-generation Histoplasma antigen assay. Antigen was detected in 16 of 19 (84%) cases of histoplasmosis and 5 of 6 (83.3%) blastomycosis cases using the second-generation assay vs. 13 of 19 (68%) and 4 of 6 (66.7%), respectively, in the original assay. Ten-fold concentration permitted detection of antigen in an additional case of histoplasmosis and another with blastomycosis, for an overall sensitivity of 23 of 25 (92.0%). Specificity was 98.2% in both assays in controls with other pulmonary infections. These findings support the diagnostic utility of the second-generation assay in patients with pulmonary histoplasmosis and blastomycosis.

Antigens, Fungal↗
PubMed2006

Cytometric analysis of BAL T cells labeled with a standardized antibody cocktail correlates with immunohistochemical staining.

BACKGROUND: Determining T-cell phenotypes of lung cells obtained by bronchoalveolar lavage (BAL) is frequently clinically useful, particularly for evaluating causes of interstitial lung disease. The current standard of determining CD4/CD8 T-cell subsets by immunohistochemical (IHC) staining of cytocentrifuge slides is labor-intensive and subject to interpreter variation. Flow cytometry (FCM) is a precise and rapid method commonly used in research to characterize cells in the lung. However, few studies address the methodology of analysis of BAL lymphocytes by FCM. METHODS: Patients underwent bronchoscopy for clinical purposes. A BAL cell differential and T-cell subtype was requested by the treating physician to supplement the evaluation of patients with suspected interstitial lung disease. We used a commercially available T-cell antibody reagent, approved for analysis of blood via FCM, for T-cell subtyping of clinical BAL specimens. RESULTS: The percentages of CD4 and CD8 T-cell populations, as well as the CD4/CD8 ratios showed excellent correlation with IHC staining of cytocentrifuge slides regardless of the acquisition program used, as long as the gating strategy remained consistent (r > or = 0.9693 for CD4, r > or = 0.9589 for CD8, and r > or = 0.9485 for the CD4/CD8 ratio). CONCLUSION: These findings validate the use of standardized, commercially available antibody cocktails for BAL lymphocyte subtyping, making this technique available to clinicians and researchers with access to a three-color or four-color flow cytometer.

Antibodies↗
PubMed2006

FEV1/FVC ratio of 70% misclassifies patients with obstruction at the extremes of age.

BACKGROUND: The American Thoracic Society recommends using the lower limit of normal (LLN) method to diagnose obstructive lung disease. However, few studies have investigated the clinical relevance of these recommendations. We compared the LLN derived from available data sets to a fixed ratio (FEV1/FVC, < 75% or 70%) and also to the FEV1/FVC percent predicted ratio to determine the impact of changing the FEV1/FVC "cutoff" on the spirometric diagnosis of obstructive lung disease. METHODS: FEV1, FVC, FEV1/FVC ratio, age, race, sex, height, and weight were recorded from 1,503 pulmonary function tests. Predicted values were calculated using the Third National Health and Nutrition Examination Study data set (Hankinson), and reference values from studies by Crapo, Knudson, and Morris. In addition, the LLN of the FEV1/FVC ratio was calculated for the Hankinson and Crapo reference values. RESULTS: The number of studies interpreted as obstructed varied from 37% using the Hankinson data set to 55% using the 75% fixed ratio method. Comparing the LLN method vs the 70% fixed ratio method resulted in 7.5% (Hankinson LLN vs 70% fixed) and 6.9% (Crapo LLN vs 70% fixed), which were discordant results. Age was the strongest predictor of discordance, and 16% of subjects > 74 years of age had discordant results comparing Hankinson values to the 70% fixed method. CONCLUSION: At the extremes of age and height, a large number of spirometry test results will be interpreted as showing an obstructive defect if a 70% fixed ratio method is used for interpretation compared with the LLN derived from the Hankinson data set.

Adolescent↗
PubMed2005

Apoptosis of CD57+ and CD57- lymphocytes in the lung and blood of HIV-infected subjects.

Patients infected with HIV frequently have a CD8+ lymphocytic alveolitis consisting of HIV-specific CD8+CD57- cytotoxic T lymphocytes. However, in late stage disease, there is expansion of a CD8+CD57+ population with suppressive properties. We examined role of lymphocyte apoptosis in the expansion of the CD8+CD57+ lymphocytes in late stage HIV in the lung and blood compartment in human subjects. Fas was expressed on virtually all lung lymphocytes from HIV-infected and normal subjects. Fas ligand expression was increased in HIV infection in both CD8+CD57+ and CD8+CD57- lymphocytes, though a significantly greater percentage of CD8+CD57+ cells expressed this marker. CD8+CD57+ lymphocytes in normal and HIV-infected subjects underwent more apoptosis than CD8+CD57- cells. However, in late stage HIV infection, the percentage of CD8+CD57+ cells undergoing apoptosis declined. These data demonstrate that under normal conditions CD8+CD57+ cells appear destined to undergo programmed cell death. Expansion of suppressive CD8+CD57+ cells in the lungs of HIV-infected subjects with advanced disease may be due to the failure of this normal regulatory process.

Apoptosis↗
PubMed2005

Impaired cell surface expression of human CD1d by the formation of an HIV-1 Nef/CD1d complex.

The HIV-1 Nef protein causes a decrease in major histocompatibility complex (MHC) class I and CD4 molecule expression on the cell surface. To determine if Nef can affect components of the innate immune response, we assessed the ability of Nef to alter the cell surface expression of human CD1d. In cells co-expressing CD1d and Nef, a substantial reduction in the cell surface level of CD1d was observed, with a concomitant reduction in the activation of CD1d-restricted NKT cells. Nef had a minimal effect on the cell surface expression of a mutant CD1d molecule in which the last 6 or 10 amino acids of the cytoplasmic tail were deleted. Additionally, it was found that Nef physically interacted with wild-type (but not tail-deleted) CD1d. Therefore, one means by which HIV-1 may be able to establish a foothold in an infected individual is by directly interfering with the functional cell surface expression of CD1d.

Antigens, CD1↗
PubMed2005

CD4+CD28-T cells are expanded in sarcoidosis.

BACKGROUND AND AIM: A subset of CD4+ lymphocytes lacking CD28, an important costimulatory molecule, is increased in certain inflammatory conditions. However, studies have not directly studied CD4+CD28-lymphocytes in patients with chronic sarcoidosis. The aim of this study was to further characterize the CD4+CD28-T cell population in patients with sarcoidosis, particularly those with active disease. METHODS: Seventeen patients with chronic sarcoidosis and 15 blood donors were studied. Bronchoalveolar lavage cells were available for paired analysis in seven sarcoid patients. In 4 sarcoid patients, adequate sample was available for intracellular cytokine analysis by flow cytometry. IFN-gamma production in plasma and BAL was determined by ELISA and cytometric bead array analysis and compared to previously studied controls. RESULTS: Peripheral blood from patients with sarcoidosis had a significantly higher proportion of CD4+CD28- cells compared with healthy donors. A higher percentage of CD4+CD28- cells was evident in the BAL relative to peripheral blood in patients with active sarcoid. IFN-gamma levels were greater both in the plasma and concentrated BAL fluid of sarcoid subjects compared to controls. The majority of IFN-gamma and TNF-alpha producing lymphocytes were CD28+ in both healthy blood donors and sarcoid subjects. CONCLUSIONS: CD4+CD28- cells are increased in the peripheral blood and lungs of patients with sarcoidosis requiring treatment. These cells may contribute to the inflammatory response; however, they are not major contributors of IFN-gamma or TNF-alpha.

Adult↗
PubMed2004

Human immunodeficiency virus gp120 downregulates CD1d cell surface expression.

CD1d is an MHC class I-like surface molecule that presents endogenous glycoplipid antigens. The effect of HIV infection on CD1d surface expression has not yet been reported. FACS analysis revealed significantly lower levels of CD1d on CD14(+) monocytes from HIV-infected subjects compared to HIV-infected subjects on HAART and healthy controls. CD1d expression correlated inversely with viral load in infected individuals. CD1d surface expression on human cell lines was downregulated after infection with M-tropic HIV, T-tropic HIV, or after exposure to HIV gp120 in vitro. These data suggest that CD1d-mediated responses are altered during HIV infection and may thus contribute to the global immunodeficiency seen in these patients.

Antigens, CD1↗
PubMed2004

Macrophages exposed to lymphotropic and monocytotropic HIV induce similar CTL responses despite differences in productive infection.

Macrophages are accessory cells that are vulnerable to infection by HIV-1. HTLV-IIIB, a lymphotropic strain of HIV, infects macrophages poorly resulting in either no or low levels of virus expression compared to high levels of productive infection after exposure of macrophages to the monocytotropic HIV strain Ada-M. Whether this results in an impaired ability of HTLV-IIIB-exposed macrophages to initiate protective cytotoxic T lymphocyte (CTL) immune responses against these strains is not well defined. We investigated the ability of monocyte-derived macrophages (MDM) exposed to lymphotropic and monocytotropic HIV strains to initiate primary CTL responses in vitro. MDM exposed to HTLV-IIIB induced a specific primary CTL response that was comparable to MDM exposed to the monocytotropic strain Ada-M despite marked differences in productive HIV infection in MDM between the two strains. CTL generated in this model were MHC-restricted, strain-specific, and CD8+. These data demonstrate that high levels of productive HIV infection in accessory cells are not a prerequisite for the generation of a primary CTL response, suggesting a novel immunologic interaction between MDM and lymphotropic HIV strains.

CD4-Positive T-Lymphocytes↗
PubMed2003

Alveolar macrophages from HIV-infected subjects are resistant to Mycobacterium tuberculosis in vitro.

HIV-infected individuals frequently develop Mycobacterium tuberculosis (MTB) infection. Alveolar macrophages (AM) are the initial host defense against this organism. We measured MTB growth in AM from normal and HIV-infected subjects after in vitro exposure. Intracellular growth of MTB was reduced in AM from HIV-infected subjects compared with normal macrophages. This was confined to subjects with CD4 counts greater than 200/microl. Growth of avirulent mycobacteria in HIV macrophages was significantly less than virulent MTB. Because avirulent MTB is more sensitive to tumor necrosis factor-alpha (TNF-alpha), we examined the relationship between cytokine secretion and mycobacterial growth. Higher AM spontaneous TNF-alpha secretion was associated with reduced MTB growth in normal AM. This relationship was not seen in HIV-infected subjects, suggesting that other factors contributed to mycobacteria resistance. Mycobacteria-induced TNF-alpha secretion was inversely associated with growth in normal AM but not in HIV-infected subjects. Finally, binding and internalization of MTB was augmented in HIV macrophages compared with normal, demonstrating that reduced intracellular MTB growth was not due to impaired phagocytosis. In conclusion, the increased incidence of MTB infection in HIV-infected subjects does not appear to be due to a defect in macrophage innate immunity.

Adult↗
PubMed2003

Histoplasmosis after treatment with anti-tumor necrosis factor-alpha therapy.

Anti-tumor necrosis factor-alpha (TNF-alpha) antibodies are frequently used to treat inflammatory diseases. However, these drugs also have immunosuppressive effects. We report on three patients who developed disseminated histoplasmosis on therapy with TNF-alpha inhibitors. In vitro assays were used to characterize the role of these agents in host defense against Histoplasma capsulatum. Intracellular proliferation of H. capsulatum was measured in alveolar macrophages and peripheral monocytes of normal volunteers in the presence and absence of the TNF-alpha antibody, infliximab. Both infliximab and control antibody enhanced fungal growth in monocytes and alveolar macrophages, suggesting this was a nonspecific antibody response. Despite similar intracellular fungal loads in the presence of both antibodies, lymphocyte proliferation in response to blood monocytes and alveolar macrophages infected with H. capsulatum was inhibited by the addition of physiologic doses of infliximab, whereas control antibody had no effect. The production of H. capsulatum-induced interferon-gamma and TNF-alpha was assessed in 5-day cultures containing lymphocytes and alveolar macrophages or monocytes. Interferon-gamma secretion was significantly reduced in the presence of infliximab. In summary, patients receiving anti-TNF-alpha therapy are at risk for developing disseminated histoplasmosis. This may be due to a defect in the TH1 arm of cellular immunity.

Adolescent↗