Immunosuppressive activity of T cell clones generated from human T cells stimulated with autologous TPHA cells

T cell clones were generated from human T cells stimulated with autologous phytohemagglutinin (PHA)-activated T (TPHA) cells. Characterization of three T cell clones originated from donor SF and one from donor JM showed that they proliferated when stimulated with autologous TPHA cells, non-T cells, and peripheral blood mononuclear cells, but did not proliferate when stimulated with allogeneic TPHA cells, non-T cells, and mononuclear cells, with autologous and allogeneic resting T cells, and with PHA. These results in conjunction with the blocking of the proliferation by anti-histocompatibility leukocyte antigen class II monoclonal antibodies indicate that these class II antigens are involved in the proliferation of T cell clones stimulated with autologous lymphoid cells. The four T cell clones are cytotoxic neither to autologous lymphoid cells nor to a panel of cultured human cell lines. The four T cell clones display immunosuppressive activity, since they inhibit the proliferation of autologous and allogeneic cells stimulated with antigens and mitogens and the secretion of immunoglobulin by B cells stimulated with pokeweed mitogen in presence of T cells. Furthermore, the four T cell clones display differential inhibitory activity on the proliferation of cultured human cell lines. The immunosuppressive activity is species-specific, since the T cell clones do not inhibit the proliferation of murine cells. The suppression is mediated by a factor(s) with an apparent m.w. of 13,000 to 16,000. The suppressor activity is labile at alkaline pH and is lost following incubation with pronase (100 U/ml) for 30 min at 37 degrees C.     

Meiobenthic distribution and nematode community structure in five European estuaries

Meiofauna from the intertidal zone of five European estuaries (Ems, Westerschelde, Somme, Gironde, Tagus) was investigated. Samples represented a cross section of various benthic habitats from near-freshwater to marine, from pure silts to fine-sandy bottoms. The meiobenthic community comprised everywhere a fauna strongly dominated by nematodes, with meiobenthic density increasing with increasing salinity. The Ems differed from the other estuaries due to the presence of a well developed community of Copepods, Gastrotrichs, large Ciliates and/or soft-shelled Foraminiferans in some sites. The Westerschelde stood out due to the near-absence of harpacticoid copepods and, as in the Tagus, the lower meiobenthic densities in the marine part of the estuary. For nematode community analysis, we also included data from the Tamar which were obtained from the literature (Warwick &; Gee, 1984). This resulted in the enumeration of 220 species, belonging to 102 genera, each with a characteristic distribution along the salinity, sedimentary and latitudinal gradients. Using the multivariate technique CANOCO, a zonation along these different physicochemical determinants was observed as well although salinity and sediment characteristic (scale of hundreds of meters to kilometers) proved to be more important in explaining community structure than latitudinal differences (scale of hundreds of kilometers). Nematode diversity was nearly entirely determined on the genus level and was positively related to salinity. Deviations from this general trend in the Gironde and the Tamar were attributed to sedimentary characteristics or to low macrobenthic predation. The presence of a typical opportunistic colonizing nematode species Pareurodiplogaster pararmatus in the low-salinity region of the Gironde could indicate (organic?) pollution or disturbance of the intertidal mud-flats.