Müllerian-inhibiting substance type II receptor expression and function in purified rat Leydig cells.

Müllerian-inhibiting substance (MIS), a gonadal hormone in the transforming growth factor-beta superfamily, induces Müllerian duct involution during male sexual differentiation. Mice with null mutations of the MIS ligand or receptor develop Leydig cell hyperplasia and neoplasia in addition to retained Müllerian ducts, whereas MIS-overexpressing transgenic mice have decreased testosterone concentrations and Leydig cell numbers. We hypothesized that MIS directly modulates Leydig cell proliferation and differentiated function in the maturing testis. Therefore, highly purified rat Leydig and Sertoli cells were isolated to examine cell-specific expression, binding, and function of the MIS type II receptor. These studies revealed that this receptor is expressed abundantly in progenitor (21-day) and immature (35-day) Leydig cells as well as in Sertoli cells. Prepubertal progenitor Leydig cells exhibit high affinity (Kd = 15 nM), saturable binding of MIS. No binding, however, is detected with either peripubertal immature Leydig cells or Sertoli cells at either age. Moreover, progenitor, but not immature Leydig cells, respond to MIS by decreasing DNA synthesis. These data demonstrate that functional MIS type II receptors are expressed in progenitor Leydig cells and support the hypothesis that MIS has a direct role in the regulation of postnatal testicular development.

Constitutive shedding of the amyloid precursor protein ectodomain is up-regulated by tumour necrosis factor-alpha converting enzyme.

The amyloid precursor protein (APP) of Alzheimer's disease is a transmembrane protein that is cleaved within its extracellular domain, liberating a soluble N-terminal fragment (sAPP alpha). Putative mediators of this process include three members of the ADAM (a disintegrin and metalloprotease) family, ADAM9, ADAM10 and ADAM17/TACE (tumour necrosis factor-alpha converting enzyme). Tumour necrosis factor-alpha protease inhibitor (TAPI-1), an inhibitor of ADAMs, reduced constitutive and muscarinic receptor-stimulated sAPP alpha release in HEK-293 cells stably expressing M3 muscarinic receptors. However, the former was less sensitive to TAPI-1 (IC(50)=8.09 microM) than the latter (IC(50)=3.61 microM), suggesting that these processes may be mediated by different metalloproteases. Constitutive sAPP alpha release was increased several-fold in cells transiently transfected with TACE, and this increase was proportional to TACE expression. In contrast, muscarinic-receptor-activated sAPP alpha release was not altered in TACE transfectants. TACE-dependent constitutive release of co-transfected APP(695) was inhibited by TAPI-1 with an IC(50) of 0.92 microm, a value significantly lower than the IC(50)s for inhibition of either constitutive or receptor-regulated sAPP alpha shedding mediated by endogenous secretases. The results indicate that TACE is capable of catalysing constitutive alpha-secretory cleavage of APP, but it is likely that additional members of the ADAM family mediate endogenous constitutive and receptor-coupled release of sAPP alpha in HEK-293 cells.

Immunoglobulin (Ig) and IgG subclasses in Asian children with bronchial asthma.

Selective immunoglobulin deficiencies have been shown to be associated with atopic disease. In this study, serum immunoglobulin (Ig) G, A, M, E and IgG subclasses of 92 Asian asthmatic children were studied and compared with those of age-matched controls. The children, aged between 0.7 and 17.4 years (mean age 7.5 years), were recruited from the National University Hospital, Singapore. The serum Ig levels were measured by enzyme-linked immunosorbent assay, except for IgE which was measured by the fluorescent allergosorbent test. As expected, serum total IgE levels were markedly higher in the asthmatic children than in the controls (geometric mean = 513 units/ml and 164 units/ml, respectively; p < 0.0001). Serum IgM levels were also slightly higher in the asthmatic patients than in the controls (geometric mean = 1.74 and 1.51 milligrams, respectively; p < 0.04). Mean serum IgG and A and IgG subclasses (1-4) levels in the asthmatics did not differ significantly from those in the controls. However, four asthmatic children were found to have selective IgA deficiency (serum IgA < 0.08 milligrams). None of the patients was found to be IgG subclass-deficient.

T cell immunodeficiency in dyskeratosis congenita.

Dyskeratosis congenita has been found to be associated with abnormal immune function. In this study we report a patient with this association. He developed Pneumocystis carinii interstitial pneumonia, and impaired cell mediated immunity was confirmed by the presence of depressed lymphoproliferative responses to in vitro stimulation with mitogen. Enumeration of T cell subsets showed a severely depressed CD4:CD8 ratio (0.38), which is the likely cause for impaired cell mediated immunity. The T cell activation pathway appeared intact, as his T lymphocytes were able to express activation markers (CD25 and HLA-DR) after mitogen stimulation.

Th1 and Th2 cytokine mRNA profiles in childhood nephrotic syndrome: evidence for increased IL-13 mRNA expression in relapse.

Idiopathic nephrotic syndrome of childhood is thought to be associated with T lymphocyte dysfunction often triggered by viral infections, with the production of circulating factor(s) resulting in proteinuria. In view of the conflicting evidence of T cell activation and Th1 or Th2 pattern of cytokine synthesis in this disease, this study examined the mRNA expression of interleukin-2 (IL-2), interferon-gamma, IL-4, and IL-13 from CD4+ and CD8+ T cells in steroid-responsive nephrotic patients in relapse and remission. Fifty-five children with steroid-responsive nephrotic syndrome were included in this study, together with 34 normal controls and 24 patient controls with viral infections. RNA was isolated from purified CD4+ or CD8+ cells from peripheral blood and subjected to reverse transcription-PCR. Cytokine mRNA expression was measured semiquantitatively, and a cytokine index was derived from densitometric readings, with cyclophilin as the housekeeping gene. Both cross-sectional and paired data showed an increased CD4+ and CD8+ IL-13 mRNA expression in patients with nephrotic relapse as compared to remission, normal, and patient controls (P < 0.008). This was also associated with increased cytoplasmic IL-13 expression in phorbol myristate acetate/ionomycin-activated CD3+ cells (6.66+/-3.39%) from patients with nephrotic relapse compared to remission (2.59+/-1.35%) (P < 0.0001). However, there was no significant difference in CD4+ or CD8+ IL-2, interferon-gamma and IL-4 mRNA expression. IL-13 is an important T cell cytokine with anti-inflammatory and immunomodulatory functions on B cells and monocytes. It is conceivable that IL-13 may act on monocytes to produce vascular permeability factor(s) involved in the pathogenesis of proteinuria in patients with relapse nephrotic syndrome.

Quantitation of peripheral blood cytomegalovirus DNA for monitoring recurrent cytomegalovirus retinitis in pediatric solid organ transplant recipients.

Cytomegalovirus (CMV) infection is a major concern following solid organ transplantation, especially in the pediatric population who remain at high risk of primary infection. CMV disease leads not only to increased patient and graft morbidity, but also to increased health care costs. This study describes the usefulness of a quantitative CMV polymerase chain reaction (PCR) technique for monitoring peripheral blood CMV DNA in pediatric recipients of kidney and liver allografts who had recurrent CMV retinitis. The incidence of CMV disease in 28 pediatric transplant recipients was 28.6%, one-half of whom developed retinitis. Two of these patients had recurrent retinitis on cessation of anti-viral treatment. A peripheral blood CMV DNA copy number of > or =500/microg of DNA was associated with recrudescence of the retinitis in these patients. We conclude that the measurement of peripheral blood CMV DNA by PCR is a useful tool for the surveillance of disease resolution and recurrence. This is particularly important in patients with CMV retinitis, who may remain asymptomatic for a period of time, despite recurrences.

Modulation of MHC expression on human endothelial cells by sera from patients with systemic lupus erythematosus.

Major histocompatibility complex (MHC) antigen expression on cells is a prerequisite for immune interaction with activated T-cells. This study examined the ability of sera from patients with systemic lupus erythematosus (SLE) to modulate MHC expression on vascular endothelial cells. SLE sera were able to selectively upregulate MHC class I antigen expression on cultured human umbilical venous endothelial (HUVE) cells, without concomitant induction of MHC class II antigen. The stimulation index (SI) for MHC class I expression produced by SLE sera (1.21 +/- 0.23) was significantly higher than those for normal controls (1.01 +/- 0.10) (P < 0.0001) and non-SLE patients (1.12 +/- 0.14) (P < 0.05). Additionally, active SLE patients had higher mean SI than inactive patients (P < 0.001). Preincubation of SLE sera with Protein A-Sepharose beads conjugated with antibodies against tumor necrosis factor-alpha and interferon-alpha was able to significantly reduce their ability to upregulate class I MHC expression by HUVE cells, indicating that these cytokines were responsible for the modulatory effect. This could be an important mechanism for the immune-mediated vascular injury seen in SLE.

Inflammatory response in bacterial meningitis: cytokine levels in the cerebrospinal fluid.

Inflammatory response plays an important role in the pathogenesis of cerebral injury in bacterial meningitis. In this study, we evaluated the cytokine levels of interleukin 1-beta (IL1 beta), tumour necrosis factor alpha (TNF alpha) and interleukin 6 (IL6) in the cerebrospinal fluid (CSF), and determined their correlation with acute clinical complications and with changes in CSF biochemistry. Interleukin 6, TNF alpha and IL1 beta were present in 9/9, 3/9 and 4/9 patients, respectively. The CSFs with detectable TNF alpha or IL1 beta had higher levels of IL6 (p < 0.02), protein (NS) and lower glucose levels (p < 0.02), compared with those in which TNF alpha and IL1 beta were absent. Tumour necrosis factor alpha and IL1 beta levels also correlated with the presence of prolonged fever, fits, spasticity and death (logTNF alpha: r = 0.70, p < 0.05; logIL1 beta: r = 0.62, p = 0.08). The cytokine levels reflect the degree of inflammatory response and are positively correlated with the severity of acute clinical complications. Modulation of this inflammatory response in bacterial meningitis may improve its morbidity and mortality.

Age- and sex-related changes in lymphocyte subpopulations of healthy Asian subjects: from birth to adulthood.

Flow cytometric analysis of lymphocyte subsets were evaluated in 391 healthy Asian subjects ranging in age from birth to 40 years. Lymphocyte subsets were analysed using specific monoclonal antibodies: CD20 (B cells), CD3 and CD2 (T cells), CD16 and CD56+ (NK cells), CD4/CD3+ (helper-inducer T cells), CD8/ CD3+ (suppressor/cytotoxic T cells), HLA-DR expression on CD3 and CD25 (Tac) on CD3. The total white cell count, absolute lymphocyte counts, and B cell percentages peaked in infancy and declined steadily with age. Absolute counts of each subset, which were derived from absolute lymphocyte counts, also followed this trend. Increases with age were seen in the NK, T cell (CD2, CD3), and CD8 percentages. Males tended to have higher NK and CD8 percentages than females, and, conversely, females had higher CD3 and CD4 percentages than males. Comparison of our results with studies involving Caucasian subjects indicated higher NK percentages in our Asian population and lower CD4 absolute counts in the males of our population. These results indicate the presence of age, sex, and probable racial differences in lymphocyte subset expression. Our results may serve as reference standards for the Asian population.