Biomedical subjects

K Lammers

Publications and source records attributed to K Lammers.

4 recordsLinked to original sources

PubMed2004

Modulation of human dendritic cell phenotype and function by probiotic bacteria.

BACKGROUND: "Probiotic" bacteria are effective in treating some inflammatory bowel diseases. However which bacteria confer benefit and mechanisms of action remain poorly defined. Dendritic cells, which are pivotal in early bacterial recognition, tolerance induction, and shaping of T cell responses, may be central in mediating the effects of these bacteria. AIMS: To assess effects of different probiotic bacteria on dendritic cell function. METHODS: Human intestinal lamina propria mononuclear cells, whole blood, or an enriched blood dendritic cell population were cultured with cell wall components of the eight bacterial strains in the probiotic preparation VSL#3 (four lactobacilli, three bifidobacteria, and one streptococcal strains). Dendritic cells were identified and changes in dendritic cell maturation/costimulatory markers and cytokine production in response to probiotic bacteria were analysed by multicolour flow cytometry, in addition to subsequent effects on T cell polarisation. RESULTS: VSL#3 was a potent inducer of IL-10 by dendritic cells from blood and intestinal tissue, and inhibited generation of Th1 cells. Individual strains within VSL#3 displayed distinct immunomodulatory effects on dendritic cells; the most marked anti-inflammatory effects were produced by bifidobacteria strains which upregulated IL-10 production by dendritic cells, decreased expression of the costimulatory molecule CD80, and decreased interferon-gamma production by T cells. VSL#3 diminished proinflammatory effects of LPS by decreasing LPS induced production of IL-12 while maintaining IL-10 production. CONCLUSIONS: Probiotic bacteria differ in their immunomodulatory activity and influence polarisation of immune responses at the earliest stage of antigen presentation by dendritic cells.

Antigen Presentation↗

PubMed1998

Variation in gut-homing CD27-negative lymphocytes in inflammatory colon disease.

Prolonged antigenic stimulation results in lymphocyte shedding of CD27, a member of the tumour necrosis factor receptor (TNFR) family, and transformation to a stable phenotype capable of synthesizing interleukin-4 (IL-4). Co-expression of alpha4beta7 identifies those cells with gut-homing potential. We have investigated these cell populations in patients with inflammatory colonic disease. Circulating and lamina propria mononuclear cells were isolated from patients with Crohn's disease (CD), ulcerative colitis (UC), non-inflammatory bowel disease (non-IBD) colonic inflammation and healthy controls. Double and triple colour flow cytometry for CD3, CD4, CD27, alpha4beta7 and intracellular cytokines was performed. Circulating CD4+ CD27- populations were increased in patients with CD (8.8 +/- 0.8%, P < 0.001), UC (12.2 +/- 1.9%, P < 0.001) and non-IBD colitis (10.5 +/- 1.3%, P < 0.01) as compared with controls (6.1 +/- 0.5%). CD4+ CD27- alpha4beta7+ cells were increased in CD (P < 0.01). Lamina propria CD4+ CD27- populations were depressed significantly in CD (P < 0.05), UC (P < 0.02) and non-IBD colitis (P < 0.03). Mucosal CD4+ CD27- cells synthesized IL-4 in preference to interferon-gamma. Thus, colonic inflammation is associated with alterations in gut-tropic circulating and mucosal populations of differentiated memory T cells with the phenotype of predominantly IL-4-synthesizing cells.

CD4-Positive T-Lymphocytes↗

PubMed1995

Engagement of CD27 with its ligand CD70 provides a second signal for T cell activation.

Molecules of the TNF-R family have been shown to be essential in the regulation of lymphocyte growth and differentiation. The TNF-R family member CD27 binds to a type II transmembrane molecule belonging to the TNF gene family (CD27L) that is identical to the lymphocyte activation Ag CD70. Using transfected mouse fibroblasts expressing human CD70, we demonstrate here that interaction of CD27 with its ligand provides a potent second signal for cytokine production, induction of activation Ags, and proliferation of unprimed CD45RA+, and to a lesser extent, of primed CD45R0+ peripheral blood T cells. In contrast to costimulatory signals delivered via the CD28-ligand B7-1 (CD80), CD70 was found to induce relatively low IL-2, IL-4, and IL-10 but comparable TNF-alpha secretion. Proliferation of CD45RA+, but not of CD45R0+ T cells, was found to be largely resistant to blocking of IL-2/IL-2R interaction. Finally, the finding that CD70 and CD80 cooperate in the induction of T cell proliferation indicates that cooperation of both molecules may be essential for optimal T cell stimulation. The interaction between CD27 and its ligand CD70 might be of particular importance for the recruitment of T cells from the unprimed T cell pool. Moreover, as CD70 expression in vivo is confined to activated B and T lymphocytes, only a limited set of APC are able to generate this specific second signal for T cell expansion.

Antibodies, Monoclonal↗

PubMed1994

Influence of CD28 co-stimulation on cytokine production is mainly regulated via interleukin-2.

Interaction of CD28 with its ligand B7 plays an important role in the initiation of immune responses. The co-stimulatory signal generated by cross-linking of CD28 molecules results in enhanced T-cell proliferation and augmentation of cytokine production. In particular, mRNA levels of T-helper 1 (Th1)-type cytokines, such as interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) are reported to be strongly increased. We investigated the effect of CD28 co-stimulation on the production of Th2-type cytokines. CD28 mAb induced a strong augmentation of IL-2 secretion in activated T-cell clones. Production of IFN-gamma was also enhanced, but the increase in IL-4 secretion was generally moderate. Augmentation of IL-4 production by CD28 was most pronounced in clones that produced low amounts of IL-2, compared to clones producing high levels of IL-2. It was found that the up-regulation of IL-4 by CD28 co-stimulation was mainly controlled indirectly via an increase of IL-2. Some clones could produce IL-4 in an IL-2-independent manner; in these situations CD28 co-stimulation had no augmenting effect on the production of IL-4. The secretion of IL-4 by peripheral blood CD4+ T cells, that were activated with B7-expressing transfectants, was also found to be dependent on IL-2. Finally, Northern blot analysis confirmed that co-stimulation of CD28 primarily affected IL-2 production, and that inhibition of IL-2/IL-2 receptor interaction abolished the augmenting action of CD28 monoclonal antibody on the production of the Th2-type cytokines IL-4, IL-5 and IL-10 and of the Th1 cytokine IFN-gamma.

Blotting, Northern↗