PNA-binding glycans are expressed at high levels on horse mature and immature T lymphocytes and a subpopulation of B lymphocytes

Symbiont Transmission onto the Cell Surface of Early Oocytes in the Deep-Sea Clam Phreagena okutanii

Symbiotic associations with beneficial microorganisms endow a variety of host animals with adaptability to the environment. Stable transmission of symbionts across host generations is a key event in the maintenance of symbiotic associations through evolutionary time. However, our understanding of the mechanisms of symbiont transmission remains fragmentary. The deep-sea clam Phreagena okutanii harbors chemoautotrophic intracellular symbiotic bacteria in gill epithelial cells, and depends on these symbionts for nutrition. In this study, we focused on the association of these maternally transmitted symbionts with ovarian germ cells in juvenile female clams. First, we established a sex identification method for small P. okutanii individuals, and morphologically classified female germ cells observed in the ovary. Then, we investigated the association of the endosymbiotic bacteria with germ cells. We found that the symbionts were localized on the outer surface of the cell membrane of primary oocytes and not within the cluster of oogonia. Based on our findings, we discuss the processes and mechanisms of symbiont vertical transmission in P. okutanii.

Novel monoclonal antibody against alphaX subunit from horse CD11c/CD18 integrin

The αX I-domain of the horse integrin CD11c was successfully expressed in Escherichia coli, purified, biochemically characterized and used as immunogen to generate murine monoclonal antibodies against horse CD11c, which are not yet commercially available. One monoclonal antibody mAb-1C4 against the αX I-domain, is an IgG2a able to interact with the recombinant I-domain, showing an EC50=2.4ng according to ELISA assays. By western blot with horse PBMCs lysates the mAb-1C4 recognized a protein of 150kDa which corresponds well with the CD11c molecule. Using immunohistochemistry in horse lymph node tissue sections, mAb-1C4 marked cells in situ, some with apparent dendritic morphology. Thus the mAb generated to a recombinant epitope from horse CD11c identified the molecule in intact cells within horse lymphoid tissue. By the labelling intensity, the histological location (paracortical and interfollicular areas) and the apparent morphology of the marked cells, we can say that these are putative horse dendritic cells (DCs). The development of a mAb to horse CD11c provides a new tool to better study the horse DC biology and opens other biotechnological avenues, such as DC targeting-based vaccines.

The Amaranthus leucocarpus lectin enhances the anti-CD3 antibody-mediated activation of human peripheral blood CD4+ T cells

Activation of CD4(+) T cells plays a main role in adaptive immune response by regulating cellular and humoral immunity via processes associated with changes in cell surface oligosaccharide receptors. Lectins are glycoproteins that specifically recognize oligosaccharides and have been used to characterize changes in oligosaccharides present on T cell surface and their effects on activation. A lectin from Amaranthus leucocarpus seeds (ALL) is specific for glycoprotein structures containing galactose-N-acetylgalactosamine and is able to bind to human and murine CD4(+) T cells, however, its effect on activation remains unclear. We examined the effect of ALL on the activation of peripheral blood human CD4(+) T cells and analyzed cell proliferation, expression of the activation-associated molecule CD25, secretion of the activation-dependent cytokine interleukin (IL)-2 and intracellular calcium influx changes using flow cytometry. CD4(+) T cells were stimulated with anti-CD3 antibodies that provided the first activation signal in the presence or absence of ALL. ALL alone did not induce CD4(+) T cell activation but when also stimulated with anti-CD3 antibodies, ALL up-regulated CD25 expression, cell proliferation, IL-2 secretion and an intracellular calcium influx in a dose-dependent manner. In addition, ALL recognized CD4(+) T cells expressing the CD69 and Ki67 molecules expressed only by activated T cells and induced production of the TH1-type cytokine interferon-gamma. Our findings indicate that ALL binds to human activated CD4(+) T cells and enhances the degree of activation of CD4(+) T cells that are stimulated with anti-CD3 antibodies. ALL provides a new tool for analyzing T cell activation mechanisms.

Amaranthus leucocarpus lectin (ALL) enhances anti-CD3-dependent activation of murine T cells and promotes cell survival

The Galβ1,3GalNAc-specific lectin from Amaranthus leucocarpus (ALL) shows a differential binding pattern on murine thymocytes, peripheral and activated CD4(+) and CD8(+) T cells. Although ALL detects activation-related changes in T cell surface carbohydrate moieties, no study has been performed to examine the effect of ALL on T cell activation. In this study, we analyzed the anti-CD3-dependent activation of murine T cells in the presence of ALL by measuring proliferation, surface activation marker expression, and IL-2 secretion using total cells from the lymph node. The results showed that ALL did not significantly induce T cell activation but did enhance anti-CD3-dependent activation of both CD4(+) and CD8(+) T cells. In addition, ALL protected T cells from spontaneous apoptosis and increased cell survival in serum-free culture conditions. Our findings indicate that ALL alone does not affect T cell activation, but do suggest that ALL has an anti-CD3-dependent co-stimulatory-like effect on T cell activation. Moreover, ALL promotes cell survival in regular and serum-free culture conditions. This study is the first report of a non-mitogenic T cell-binding lectin that can induce a possible costimulatory-like effect and provides a new tool for understanding how glycosylation impacts the T cell response.

Rational design of synthetic peptides to generate antibodies that recognize in situ CD11c(+) putative dendritic cells in horse lymph nodes

A three-dimensional model of the alphaX I-domain of the horse integrin CD11c from dendritic cells provided information for selecting two segments of the primary structure for peptide synthesis. Peptide 1 contains 20 amino acids and peptide 2 has 17 amino acid residues. The first spans from position Thr229 to Arg248 of an alpha-helix segment of the structure, whereas peptide 2 goes from Asp158 to Phe174 and corresponds to an exposed segment of the loop considered to be the metal ion-dependent adhesion site. Murine polyclonal antisera against both peptides were generated and assayed in peripheral blood cell suspensions and in cryosections of horse lymph nodes. Only the serum against peptide 2 was capable of identifying cells in suspension and in situ by immunohistochemistry, some with evident dendritic morphology. Using this approach, an immunogenic epitope exposed in CD11c was identified in cells from horse lymph node in situ.