Jahn Hu

Immunological and trophical effects of Saccharomyces boulardii on the small intestine in healthy human volunteers.

Saccharomyces boulardii (S.b.) is used for the prevention and treatment of diarrhea of different etiologies. We prospectively investigated the effects of S.b. on lymphocytes and duodenal mucosa. Before and after oral administration of S.b. for 3 weeks, circulating and intestinal lymphocytes were isolated and characterized by flow cytometry. Trophic effects on duodenal mucosa were investigated by morphometry and determination of brush border enzyme activity. Results were compared intraindividually before and after S.b. In intestinal lymphocytes no phenotypic changes were observed. CD4+ cells of the peripheral blood had a significantly increased expression of CD25 (p < 0.02). None of twelve volunteers had an increase in villous surface area (n.s.). Immunoglobulin A content in small intestine secretion was unaltered. An increase in brush border enzyme activity of lactase, alpha-glucosidase, and alkaline phosphatase was observed (p < 0.01). Our findings indicate that S.b. has a positive effect on the maturation of enterocytes and only a minor influence on lymphocytes.

Detection of antibodies against viral capsid proteins of human herpesvirus 8 in AIDS-associated Kaposi's sarcoma

Abstract Sequences of a new herpesvirus with homology to gammaherpesvirinae were recently identified in AIDS-associated Kaposi’s sarcoma (KS). Subsequently this novel virus, called KS-associated virus (KSHV) or human herpesvirus (HHV) 8 was detected in classical KS and AIDS-associated body cavity based lymphomas by polymerase chain reaction. In this report major and minor capsid proteins of HHV-8 were molecularly cloned and produced as recombinant proteins in Escherichia coli. Sera from 69 HIV-1 infected patients with KS, 30 HIV-1 infected patients without KS and 106 control individuals were tested by enzyme-linked immunosorbent assay for anti-HHV-8 capsid IgM and IgG antibodies. Sera from four patients were tested over periods ranging from 18 months to 6 years. IgG antibodies directed against HHV-8 capsid antigens were detected in patients with AIDS-associated KS and in some AIDS patients without KS. Seroconversion with IgM and IgG antibodies directed against HHV-8 capsid proteins occurred more than 1 year prior to diagnosis of KS. In a considerable portion of KS patients no IgM or IgG antibodies against HHV-8 capsid proteins were detected. In these patients there was an inverse relationship between antibodies against HHV-8orf26 and the CD4/CD8 ratio, suggesting that the inconsistency of anti-HHV-8orf26 antibodies is due at least partly to an impaired immune response. No reactivity against HHV-8 capsid antigens was detected in the vast majority of sera from HIV-negative control individuals. Our findings indicate that a specific humoral immune response against capsid proteins is raised in HHV-8 infected individuals, and that anti-capsid antibodies can be used to diagnose HHV-8 infection. The correlation between occurrence of anti-HHV-8 antibodies and KS supports the hypothesis of a causative role of HHV-8.

Phenotype and function of lamina propria T lymphocytes

Summary and ConclusionsLamina propria T cells have a low expression of the CD45RA antigen and a high expression of the CD45RO antigen. This phenotype is characteristic for memory T cells (table 2). In addition, T cells in the effector compartment of the mucosa bear surface antigens which are very rarely found in other sites of the immune system. Intestinal T cells also express functional IL-2 receptors and IL-2 receptor α chain mRNA, and are able to synthesize high amounts of IL-2. However, another marker of memory T cells, CD29, is not expressed in high density in the lamina propria indicating that lamina propria T cells differ from ‘classical’ memory T cells. This is supported by functional studies in nonhuman primates infected rectally withC. trachomatis which show that lamina propria T cells do not proliferate after stimulation with antigen but rather provide helper function for immunoglobulin synthesis (table 2).The intestinal lamina propria therefore contains highly specialized T cells which have a distinctive phenotype and are activated. Functionally these T cells can be characterized as differentiated effector lymphocytes which respond to triggering the antigen-specific T cell receptor by secreting helper factors for B cells. This concept is supported by recent studies showing that the pattern of lymphokines produced by lamina propria T cells and the responsiveness to certain lymphokines differ from those of other lymphocyte populations [25]. Lamina propria T cells thus represent a subset of memory T cells with a unique maturational state.

Phenotype of HML-1-positive and HML-1-negative T lymphocytes in the human intestinal lamina propria.

Intestinal lymphocytes encounter antigen in the afferent limb of the gut-associated lymphoid tissue (i.e. the Peyer’s Patches of the small intestine and the lymphoid follicles of the colon and rectum) and then recirculate to the efferent limb, comprising lymphocytes in the epithelium above the basement membrane (intraepithelial lymphocytes) and lymphocytes diffusely spread in the lamina propria (lamina propria lymphocytes, LPL). LPL thus are antigen-activated lymphocytes. In this regard they resemble the so-called memory cells, which differentiate from naive (or virgin) precursor cells upon antigenic stimulation. We therefore postulated that LPL might represent a tissue-specific subpopulation of memory cells.