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M C Sneller

Publications and source records attributed to M C Sneller.

At least 55 records · Page 3Linked to original sources
PubMed1996

Virtual bronchoscopy: segmentation method for real-time display.

Computed tomography (CT) data sets obtained in 14 patients were used in a segmentation method for virtual bronchoscopy (VB). The method constrained the distance of propagation of a region-growing algorithm. The resulting three-dimensional bronchial model was a faithful representation of the source CT data and could be manipulated in real time at frame rates of one to two frames per second. Preliminary data showed that 90% of bronchi (up to third order) measureable on multiplanar CT reformations were also measurable at VB. The bronchial diameters measured at VB were within 1 mm of those measured on multi-planar reconstructions of the CT data.

Adult↗
PubMed1995

An analysis of forty-two Wegener's granulomatosis patients treated with methotrexate and prednisone.

OBJECTIVE: To determine the efficacy of low-dose methotrexate (MTX) plus prednisone in the treatment of Wegener's granulomatosis (WG). METHODS: An open-label study of weekly low-dose MTX plus prednisone for the treatment of WG was performed. Forty-two patients who did not have immediately life-threatening disease were enrolled into the study. Outcome was determined by clinical characteristics and pathologic, laboratory, and radiographic findings. RESULTS: Weekly administration of MTX and prednisone resulted in remission of disease in 30 of the 42 patients (71%). The median time to remission was 4.2 months. The estimated median time to relapse for all patients in whom remission was achieved was 29 months. Eight patients who had relapses were treated with a second course of MTX plus prednisone, and a second remission was induced in 6 of the 8 (75%). CONCLUSION: Weekly low-dose MTX was shown in this study to be an acceptable alternative form of therapy for selected patients with WG who do not have immediately life-threatening disease or who have developed serious cyclophosphamide-associated toxicity.

Administration, Oral↗
PubMed1994

Treatment of glucocorticoid-resistant or relapsing Takayasu arteritis with methotrexate.

OBJECTIVE: To identify the role of methotrexate (MTX) in the treatment of persistent or recurrent Takayasu arteritis that is refractory to treatment with glucocorticoids (GC) alone. METHODS: An open-label pilot study of weekly low-dose MTX+GC treatment was performed. Outcome was evaluated according to clinical characteristics, laboratory abnormalities, findings on routinely performed angiographic studies, and ability to withdraw GC and MTX therapy. Eighteen patients entered the study; 2 dropped out, and 16 were followed up for a mean period of 2.8 years (range 1.3-4.8 years). RESULTS: Weekly administration of MTX (mean stable dose of 17.1 mg) and GC resulted in remissions in 13 of 16 patients (81%). However, 7 patients (44%) had relapses as GC was tapered to or near discontinuation. Retreatment again led to remission, and 3 of 7 patients in this group have successfully stopped GC therapy. Of those patients who achieved remission, 8 (50%) have sustained remissions of 4-34 months (mean 18 months), and 4 of this group have not required GC or MTX therapy for 7-18 months (mean 11.3 months). Three patients experienced disease progression in spite of treatment. CONCLUSION: About half of all Takayasu arteritis patients have chronic active disease for which GC therapy alone does not provide sustained remissions that allow withdrawal of treatment. Weekly low-dose MTX is an effective means of inducing remission and minimizing GC therapy and toxicity in most of these patients. Further long-term studies will be required to assess the durability of remission and the need for maintenance MTX therapy in this subset of Takayasu arteritis patients.

Adolescent↗
PubMed1994

Complications of corticosteroid therapy.

The biochemistry and pharmacology of corticosteroids are reviewed as related to their clinical use, inclusive of head and neck disease. Complications and their management are discussed, as is a dosage regimen considered useful for most patients. Alternate-day corticosteroid therapy is stressed, especially in the long-term management of autoimmune and inflammatory disorders.

Anti-Inflammatory Agents↗
PubMed1994

A unique syndrome of immunodeficiency and autoimmunity associated with absent T cell CD2 expression.

CD2 is a glycoprotein expressed on the surface of human T cells that mediates adhesion between T cells and antigen presenting cells. CD2 also functions in concert with the T cell receptor to transduce signals that lead to T cell activation. The CD8 and CD4 molecules are transmembrane glycoproteins that are expressed on mutually exclusive populations of mature T cells and bind to determinants on major histocompatibility complex class I and class II molecules respectively. Like CD2, CD4 and CD8 function to promote adhesion between T cells and antigen presenting cells and potentiate signaling via the T cell receptor. We studied a patient with idiopathic lymphopenia and disseminated infection with Mycobacterium avium. The patient also suffered from recurrent deep venous thrombosis in association with anticardiolipin and anti-DNA antibodies. Peripheral blood T cells from this patient were polyclonal and expressed no detectable CD2 RNA or protein as determined by northern blotting, immunofluorescent staining with anti-CD2 antibodies, and failure to form rosettes with sheep red blood cells. In addition, the majority (85%) of this patient's T cells did not express either CD4 or CD8 but did express the alpha/beta T cell receptor. T cells from this patient failed to respond to stimulation with alloantigen or specific antigen. In contrast, there was a normal response to stimulation with immobilized anti-CD3 antibody. The clinical and immunologic findings in this patient provide in vivo evidence that the accessory molecules CD2, CD4, and CD8 play important roles in the regulation of normal human T cell activation.

Antigens, Surface↗
PubMed1994

Common variable immunodeficiency: diagnosis and management.

OBJECTIVE: Common variable immunodeficiency is a heterogeneous syndrome characterized by humoral immunodeficiency, recurrent bacterial infections, and a variety of immunologic abnormalities. The goal of this article is to review the pathogenesis, clinical manifestations, diagnosis, and management of common variable immunodeficiency. DATA SOURCES: References are limited to the English language literature. Sources include computerized databases and bibliographies of recent articles and books. STUDY SELECTION: References that made important contributions to our understanding of the pathogenesis, clinical manifestations, diagnosis, and treatment of this disease were selected for inclusion in this review. RESULTS AND CONCLUSION: Common variable immunodeficiency is an idiopathic state of immune dysregulation that results in impaired antibody synthesis and the development of recurrent bacterial infections. This syndrome is also associated with a variety of autoimmune and neoplastic disorders. Effective management of these patients includes intravenous immunoglobulin replacement, vigorous treatment of infections, and readiness to promptly evaluate and treat unusual autoimmune and neoplastic complications should they appear.

Common Variable Immunodeficiency↗
PubMed1993

Functional abnormalities of CD8+ T cells define a unique subset of patients with common variable immunodeficiency.

A substantial subgroup of patients with common variable immunodeficiency (CVI) exhibit an abnormal T-cell phenotype characterized by a low CD4/CD8 ratio associated with a significant increase in the absolute number of CD8+ T cells (CVI4/8low patients). In the present study, we examined the phenotypic and functional properties of purified T-cell subsets in this group of CVI patients. CD8+ T cells from CVI4/8low patients manifested increased expression of HLA-DR and CD57 and decreased expression of CD45RA as compared with CD8+ T cells from normal controls. When stimulated with anti-CD3 and phorbol 12-myristate 13-acetate, purified patient CD8+ T cells exhibited significantly decreased proliferation, c-myc expression, and interleukin-2 (IL-2) production compared with that of normal CD8+ T cells. Nevertheless, mitogen-activated patient CD8+ T cells secreted elevated amounts of gamma-interferon and IL-5 and normal amounts of IL-4. This abnormal pattern of proliferation and cytokine production was limited to the CD8+ T-cell subset as CD4+ T cells from these patients exhibited normal proliferation and cytokine production. In further functional studies, purified CD8+ T cells from CVI4/8low patients manifested increased cytotoxic T-lymphocyte activity and suppressor activity, as compared with normal CD8+ T cells, when they were tested in (1) an anti-CD3 "redirected" cytotoxicity assay and (2) a suppressor assay consisting of CD8+ T cells and Staphylococcus aureus Cowan I (SAC) plus IL-2-stimulated normal (allogeneic) B cells. In the latter case, patient CD8+ T cells suppressed IgG production, but not IgM production. Finally, in studies to evaluate the role of patient CD8+ T cells in the pathogenesis of hypogammaglobulinemia, we determined the capacity of SAC and IL-2 to induce Ig production in highly purified patient B cells, ie, in the absence of patient CD8+ T cells. We found that, whereas B cells from one patient produced normal amounts of IgG, B cells from three patients were unable to produce normal amounts of IgG under these conditions. These data establish the phenotypic and functional characteristics of CD8+ T cells in CVI4/8low and clearly distinguish CVI4/8low patients from other patients with this syndrome. The data do not support the contention that hypogammaglobulinemia in CVI4/8low patients is due to a direct effect of CD8+ T cells on terminal B-cell differentiation, except in the occasional patient. The abnormal CD8+ T cells may, nevertheless, have more subtle effects of lymphoid function that play a role in disease pathogenesis.

Antibody Formation↗
PubMed1993

NIH conference. New insights into common variable immunodeficiency.

Common variable immunodeficiency (CVI) is a heterogenous immunodeficiency syndrome characterized by hypogammaglobulinemia, recurrent bacterial infections, and various immunologic abnormalities. In addition to recurrent infections, patients with this syndrome also have an increased incidence of autoimmune disease and malignancy. Because the spectrum of associated diseases is broad, patients with CVI are seen by various medical specialists. This review discusses the pathogenesis, clinical manifestations, diagnosis, and treatment of CVI.

B-Lymphocytes↗
PubMed1993

Molecular analysis of double isotype expression in IgA switching.

In this and previous studies we have shown that during the course of B cell isotype differentiation occurring in the CH12.LX B cell line, small numbers of cells appear that bear both membrane (m)IgM and membrane IgA. We have cloned relatively stable populations of such dual-bearing cells and have performed studies to determine their molecular status. In the study of one such subclone (CH12.LX.7.10), we show by primer extension that both mu and alpha mRNA contain identical VHDJH gene segments. In complementary studies of another such subclone (CH12.LX.7.13), we show using DNA restriction fragment analysis, that the C mu gene segment, but not the C alpha gene segment, is associated with the JH gene segment. Additionally, Northern blot analysis of productive message of this clone shows that both mu and alpha mRNA cohybridize to the same VH region-specific probe. Taken together, these data suggest that CH12.LX mIgM/mIgA dual-bearing cells occur in the absence of C mu gene segment deletion and that the mu and alpha mRNA transcripts are derived using an alternative mechanism such as transplicing or alternative splicing of a long RNA transcript. On the assumption that these clones are representative of mIgM/mIgA dual-bearing cells appearing during CH12.LX IgM to IgA isotype differentiation, these data support the idea that B cells simultaneously produce mu and alpha mRNA transcripts during one stage of IgA isotype switching.

Animals↗
PubMed1993

T-cell abnormalities in common variable immunodeficiency.

Common variable immunodeficiency (CVI) is a heterogeneous condition marked by a number of different immunologic defects. One group of patients, perhaps 60% of the CVI group as a whole, is characterized by T cells that produce reduced amounts of IL-2 (mRNA and protein product), IL-4, and IL-5 (mRNA) when stimulated with phytohemagglutinin. This defect does not extend to all lymphokines, however, because the cells produce normal amounts of interferon-gamma (mRNA and protein product) when exogenous IL-2 is present. Recently, we have reexamined the T cell lymphokine production defect using a panoply of T-cell activation stimuli and have shown that the defect is a subtle one that depends on activation of the cell via the CD3-T-cell receptor complex. Because T cells proliferate normally when stimulated via this receptor, this finding suggests the presence of a "downstream" defect, perhaps one involving the factors that are necessary for activation of lymphokine genes. A second form of CVI, in this case involving approximately 30% of the CVI group as a whole, is characterized by a reduced CD4/CD8 ratio and elevated numbers of CD8+ T cells bearing the CD57 marker. Although the CD4+ T cells in this patient group elaborate normal amounts of IL-2 under various activation conditions, their CD8+ T cells produce increased amounts of interferon-gamma. Furthermore, the CD8+ T cells in this case act as "suppressor" T cells, which suppress IgG production but not IgM production of purified (normal) SAC+, IL-2-induced B cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigens, CD↗
PubMed1992

Lymphoproliferative lesions in patients with common variable immunodeficiency syndrome.

We reviewed our experience with 30 nodal and extranodal lymphoid lesions from 17 patients with common variable immunodeficiency (CVID). Immunohistochemical studies were performed on biopsies from 15 patients, in situ hybridization for Epstein-Barr virus in nine cases, and gene rearrangement analysis on seven lesions. The biopsies were classified into four groups: malignant lymphoma (two cases); atypical lymphoid hyperplasia (eight cases); reactive lymphoid hyperplasia (14 cases); and chronic granulomatous inflammation (six cases). The two malignant lymphomas were diagnosed using histologic criteria; tissue was not available for the assessment of clonality. In one neoplasm, Epstein-Barr virus was identified in the tumor cells by in situ hybridization. The cases of reactive lymphoid hyperplasia and chronic granulomatous inflammation had no atypical architectural, cytologic, or immunohistochemical features. The cases of atypical lymphoid hyperplasia were of particular interest, as these patients had either widespread involvement or massive disease. The diagnosis of lymphoma was considered likely by the clinicians and, in three cases, the histologic slides were originally interpreted as malignant lymphoma by the referring pathologists. Although the architecture of these lesions appeared to be effaced on hematoxylin and eosin-stained sections, immunohistochemical analysis demonstrated preserved architecture with florid expansion of B-cell and T-cell compartments. In addition, clinical follow-up of these patients was benign, and gene rearrangement analysis in three lesions revealed no evidence of clonality. We conclude that the majority of lymphoid lesions in patients with CVID are benign. Immunohistochemical and gene rearrangement studies are particularly helpful in the assessment of cases of atypical lymphoid hyperplasia.

Adolescent↗
PubMed1992

A novel lymphoproliferative/autoimmune syndrome resembling murine lpr/gld disease.

In mice, the two distinct autosomal recessive genes lpr and gld can induce a syndrome characterized by autoantibody formation and the progressive accumulation of an unusual CD4-CD8- T cell population in peripheral lymphoid tissue. This phenotype does not precisely mirror any human disease. In this report we describe two patients with a progressive lymphoproliferative disorder associated with autoimmunity. The peripheral blood and lymph nodes of these patients contained large numbers of an unusual CD4-CD8- T cell population. These CD4-CD8- T cells express surface markers characteristic of mature peripheral blood T cells (CD3, CD2, CD5), express the alpha/beta form of the T cell receptor, and do not express surface markers characteristic of immature thymocytes (CD1) or NK cells (CD16, CD56). Functionally, these cells exhibited deficient proliferation and lymphokine production upon stimulation with mitogenic antibodies to CD3 or CD2. Both proliferation and lymphokine production could be augmented by co-stimulation with an antibody directed at the CD28 determinant. The clinical and immunological features of this syndrome resemble the lymphoproliferative/autoimmune disease seen in lpr and gld mice.

Animals↗
PubMed1991

IgA deficiency.

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Autoantibodies↗
PubMed1990

Abnormalities of lymphokine gene expression in patients with common variable immunodeficiency.

Common variable immunodeficiency (CVI) is a syndrome characterized by hypogammaglobulinemia, recurrent bacterial infections, and increased occurrence of both autoimmune disease and malignancy. In our study we examine the expression of lymphokine genes in mitogen-activated T cells from four patients with CVI. T cells from patients with CVI did not differ significantly from normals in total T cell number, CD4/CD8 ratio, CD45R expression, or proliferation in response to PHA. However, T cells from this group of patients did exhibit significant abnormalities of mitogen-induced lymphokine gene expression. T cells from patients exhibited significantly decreased expression of IL-2, IL-4, IL-5, and IFN-gamma when compared to normal controls. In contrast to these abnormal findings, mitogen-activated T cells from patients with CVI expressed normal amounts of IL-2R alpha and c-myc suggesting that these patients have a selective abnormality of T cell activation. Furthermore, it is likely that the deficient production of IFN-gamma by patient T cells is partially due to the abnormality of IL-2 production as the levels of IFN-gamma mRNA detected during the initial IL-2-independent phase of T cell activation were normal and the addition of exogenous rIL-2 was able to normalize IFN-gamma production by PHA-stimulated patient cells. Finally, supernatants from PHA-activated cultures of patients PBMC were deficient in their ability to support Ig secretion by Staphylococcus A Cowan's-activated normal B cells suggesting that these T cell abnormalities may contribute to the pathogenesis of this syndrome.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1990

T cells in inductive and effector compartments of the intestinal mucosal immune system of nonhuman primates differ in lymphokine mRNA expression, lymphokine utilization, and regulatory function.

To define further the basis of T cell function in the inductive and effector limbs of the normal intestinal immune system, the capacity of mucosal lymphocytes to produce and use lymphokines and their effects on regulation of Ig production were determined in normal nonhuman primates. Northern blots of RNA from mitogen-activated lamina propria T cells contained more mRNA for IL-2 and IFN-gamma than did mesenteric lymph node T cells. In comparison with lymphocytes from peripheral sites, there was high expression of IL-4 and IL-5 mRNA in both mesenteric lymph node and lamina propria T cells. In studies of lymphokine utilization, T cells from lamina propria had high IL-2-induced but no IL-4-induced proliferative responses. In contrast, mesenteric lymph node T cells had high IL-4-induced and lower IL-2-induced proliferative responses compared with lamina propria T cells. Lamina propria T cells had higher helper activity in PWM-stimulated cultures and exhibited less inhibition by IL-4 than did mesenteric lymph node T cells. These data and previous studies suggest that T cells in an inductive site such as the mesenteric lymph node are a mixed population containing both "naive" cells with low potential for IFN-gamma and IL-2 production and differentiated cells with high potential for IL-4 and IL-5 production. In contrast, the data suggest that T cells in the effector compartment of the lamina propria are comprised primarily of differentiated "memory" cells that produce high levels of IL-2, IFN-gamma, IL-4, and IL-5, have high helper activity, and have a more limited ability to proliferate in response to lymphokines such as IL-4.

Animals↗