Particle concentration fluorescence immunoassay for measuring interleukin-6 receptor numbers

Analysis of the number of receptors per cell and the affinity of the ligand/receptor interaction has provided considerable insight into the functioning of numerous cytokines. Interleukin-6 (IL-6) is a multifunctional cytokine which may have considerable clinical relevance in inflammatory or immunodeficiency diseases. Using particle concentration fluorescence immunoassay (PCFIA) technology, an assay is described which calculates the receptor number and affinity on small numbers of human cells. Resting B cells are shown to lack IL-6 receptors but activation of B cells induces up to 1,300 receptors per cell, with Kd of 1 x 10(-11) to 2 x 10(-11) M. Other recombinant mediators do not alter the binding of labeled IL-6 to the cells. PCFIA avoids the use of radioactivity and requires very small numbers of cells (2 x 10(4) per well). Potential application to the study of regulatory mechanisms and to clinical situations where small samples of blood are available is feasible.     

Nematode parasitism in a Danish drosophilid community: further evaluation of the disproportionate parasitism hypothesis

The nematodes Parasitylenchus diplogenus and Howardula aoronymphium (Allantonematidae) are parasites of drosophilids (Diptera). Nematodes were found in 3/14 drosophilid species sampled in Danish woodlands: Drosophila phalerata Meigen (3.5% parasitism) was parasitized by H. aoronymphium and D. obscura Fallén (0.5%) and D. subobscura Collin (2.1%) by P. diplogenus. Parasitism was generally rare, and few drosophilid species parasitized, compared to elsewhere in Europe. Parasitism was positively correlated with relative host abundance both within Denmark and across communities, suggesting that species diversity is promoted by a disproportionately high parasitism of more common host species. The prevalence of H. aoronymphium, but not P. diplogenus, parasitism is positively related to temperature across communities.