Paired opposing leukocyte receptors recognizing rapidly evolving ligands are subject to homogenization of their ligand binding domains

Some leukocyte receptors come in groups of two or more where the partners share ligand(s) but transmit opposite signals. Some of the ligands, such as MHC class I, are fast evolving, raising the problem of how paired opposing receptors manage to change in step with respect to ligand binding properties and at the same time conserve opposite signaling functions. An example is the KLRC (NKG2) family, where opposing variants have been conserved in both rodents and primates. Phylogenetic analyses of the KLRC receptors within and between the two orders show that the opposing partners have been subject to post-speciation gene homogenization restricted mainly to the parts of the genes that encode the ligand binding domains. Concerted evolution similarly restricted is demonstrated also for the KLRI, KLRB (NKR-P1), KLRA (Ly49), and PIR receptor families. We propose the term merohomogenization for this phenomenon and discuss its significance for the evolution of immune receptors

Health Behavior and Lifestyle Trends among Platelet Donors: Results from a Questionnaire-Based Survey in Norway

Background. Blood donors are on average healthier than the general population, a phenomenon known as the “healthy donor effect.” Earlier studies have also pointed to healthier behaviors among whole blood donors than the general population. This study is aimed at assessing the prevalence of four healthy behaviors (sufficient physical activity, avoiding cigarette smoking, low to moderate alcohol use, and maintaining a healthy weight) among platelet donors and to compare the results with those in the general population of similar ages. Methods. Eighty-six platelet donors were asked to complete a questionnaire designed to assess physical activity, smoking, and alcohol use. Sociodemographic information including gender, age, and education was also collected from all participants. Chi-square statistics and logistic regression were used in statistical analysis. Results. The mean age of the study donors was 51 years, 56% were female. Most were employed (90%), and 48% hold a bachelor’s or higher degree. The prevalence of healthy behaviors differed by education gradients but not by gender and age. About 49% of the donors met the weekly physical activity recommendations, less than 5% were daily smokers, and~26% were classified as more frequent drinkers (≥1 to ≤5 times per week). The corresponding percentages for the general population were, respectively, 33%, 13%, and 35%. The prevalence of overweight and obesity, as assessed by body mass index (BMI), among donors were 50% and 29%, respectively, much higher than the current prevalence of overweight and obesity of 37% and 19%, respectively, among adults in the general population. Conclusions. The individual health behaviors of the majority of the study population could be characterized by a relatively high level of physical activity, low prevalence of daily smoking, and moderate alcohol drinking. The above-average overweight/obesity prevalence among platelet donors in this cohort is of concern because of the potential serious health consequences and it warrants further reflection

Rat Macrophage C-Type Lectin Is an Activating Receptor Expressed by Phagocytic Cells

<div><p>Macrophage C-type lectin (MCL) is a membrane surface receptor encoded by the Antigen Presenting Lectin-like gene Complex (APLEC). We generated a mouse monoclonal antibody for the study of this receptor in the rat. We demonstrate that rat MCL is expressed on blood monocytes and neutrophils, as well as on several tissue macrophage populations, including alveolar and peritoneal cavity macrophages. We also demonstrate MCL expression on a subset of resident spleen macrophages. Immunohistochemistry analysis of the spleen showed staining specifically in the marginal zone and red pulp. Exposure to pro-inflammatory mediators or to yeast cell wall extract (zymosan) increased surface MCL expression on peritoneal macrophages. We characterized a rat myeloid cell line, RMW, which expresses high levels of MCL. We found that MCL co-immunoprecipitated with the activating adaptor protein FcεRIγ in these cells. Moreover, beads coated with anti-MCL antibody increased phagocytosis in the RMW cells. Together, these observations indicate that rat MCL is a receptor that activates phagocytosis in myeloid cells under inflammatory conditions.</p> </div

RMW is a rat myeloid cell line. A–D

<p>TEM ultrastructure of RMW cells. M: mitochondria. LB: lipid bodies. RER: rough endoplasmic reticulum. MV: multivesicular endosomes. G, Golgi. <b>E</b>, Flow cytometry analysis of RMW surface markers. Solid lines show the indicated surface markers; grey filled histograms correspond to isotype control.</p

Immunostaining of rat spleen.

<p>Serial-cut frozen sections were stained with mAbs towards <b>A,</b> rat MCL <b>B,</b> rat CD169 <b>C,</b> rat MHC class II <b>D,</b> human MHC class I (negative control) and visualized with peroxidase-conjugated secondary antibody and DAB substrate. RP: red pulp. PALS: periarteriolar lymphoid sheath. FOLL: follicle. MZ: marginal zone.</p

Rat MCL is expressed on monocytes, macrophages and granulocytes. A,

<p>mAb WEN42 is specific for MCL. The specificity of WEN42 was tested in flow cytometry analysis of BWN3G cells stably expressing rat MCL or Mincle. <b>B,</b> Flow cytometry analysis of rat MCL surface expression on different cell types isolated from different organs, as indicated. Histograms display cell subsets gated as described in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0057406#s2" target="_blank">materials and methods</a> section. Black line histograms: MCL. Filled grey histograms: isotype control.</p

Phagocytosis of anti-MCL-coated beads. A,

<p>Comparative surface expression of the receptors, numbers represent median fluorescence intensity. <b>B.</b> Imaging flow cytometry analysis of a RMW cell showing a cell interacting with two beads. Channel 1 shows visible light image; bead-fluorescence is shown in channel 10, with DyLight-594 counterstaining in channel 4. Black arrowhead shows an internalized bead (green fluorescence) <b>C</b>. Percentage of cells with internalized beads, or with only surface-bound beads. <b>D.</b> Efficiency of phagocytosis expressed as a ratio of cells phagocytosing beads to cells with only surface-bound beads. 10,000 cells events were collected.</p

Regulation of MCL surface expression under the effect of different stimuli.

<p><b>A,</b> Rats were injected intraperitoneally with zymosan, peritoneal cells were obtained after 24 h and stained with mAbs for flow cytometry analysis. Discontinuous line histogram shows staining in the zymosan treated group, dotted line histogram shows MCL staining in the PBS control group. Histograms display MCL expression on granular cells (including mast cells, eosinophils and neutrophils) and macrophages (MΦ) as indicated. The MCL⁺ fraction of granular cells likely reflects influx of neutrophils from the blood. MFI values are shown, calculated as the median of the fluorescence intensity. <b>B,</b> Resident peritoneal macrophages were cultured overnight with the indicated substances. Solid line histogram shows MCL staining. Grey filled histograms correspond to isotype controls.</p