IL-21 promotes survival and maintains a naive phenotype in human CD4+ T lymphocytes

IL-21 is a key T-cell growth factor (TCGF) involved in innate and adaptive immune response. It contributes to the proliferation of naive, but not memory T lymphocytes. However, the full spectrum of IL-21 activity on T cells remains unclear. Here, we demonstrate that IL-21 primarily maintains the expression of specific naive cell surface markers such as CD45RA, CD27, CD62L and CCR7 on human CD4(+) T lymphocytes and that the expression of CCR7 induces cell migration by means of CCL21 chemoattraction. These effects contrast with those of IL-2 which induced the marked proliferation of CD4(+) T lymphocytes, leading to an activated-memory phenotype. Nevertheless, IL-21 maintained cell cycle activation and expression of proliferation markers, including proliferating cell nuclear antigen and Ki-67, and triggered T-cell proliferation via TCR and co-stimulation pathways. Unlike IL-2, IL-21 decreased the expression of the anti-apoptotic Bcl-2 protein, which correlated with the absence of activation of the phosphatidylinositol 3'-kinase/Akt signaling pathway. Thus, IL-21 is a TCGF whose function is the preservation of a pool of CD4(+) T lymphocytes in a naive phenotype, with a low proliferation rate but with the persistence of cell cycling proteins and cell surface expression of CCR7. These findings strongly suggest that IL-21 plays a part in innate and adaptive immune response owing to homeostasis of T cells and their homing to secondary lymphoid organs.     

Alpha2‐adrenergic receptor activation regulates cortical interneuron migration

Monoamines such as serotonin and dopamine have been shown to regulate cortical interneuron migration but very little is known regarding noradrenaline. Similarly to other monoamines, noradrenaline is detected during embryonic cortical development and adrenergic receptors are expressed in transient embryonic zones of the pallium that contain migrating neurons. Evidence of a functional role for the adrenergic system in interneuron migration is lacking. In this study we first investigated the expression pattern of adrenergic receptors in mouse cortical interneuron subtypes preferentially derived from the caudal ganglionic eminences, and found that they expressed different subtypes of adrenergic receptors. To directly monitor the effects of adrenergic receptor stimulation on interneuron migration we used time‐lapse recordings in cortical slices and observed that alpha2 adrenergic receptors (adra2) receptor activation inhibits the migration of cortical interneurons in a concentration‐dependent and reversible manner. Furthermore, we observed that following adra2 activation the directionality of migrating interneurons was significantly modified, suggesting that adra2 stimulation could modulate their responsiveness to guidance cues. Finally the distribution of cortical interneurons was altered in vivo in adra2a/2c‐knockout mice. These results support the general hypothesis that adrenergic dysregulation occurring during embryonic development alters cellular processes involved in the formation of cortical circuits.     

Interleukin 2-independent stimulation of rabbit chondrocyte collagenase and prostaglandin E2 production by an interleukin 1-like factor

In the present study, interleukin 1 (IL 1)-containing media from different sources, namely a murine macrophage cell line (P388D1), rabbit peritoneal macrophages, and human peripheral blood mononuclear cells, were compared for their effect on thymocyte proliferation and on collagenase and PGE2 secretion by chondrocytes. A high correlation was found between the enhancement of thymocyte proliferation and the induction of collagenase and PGE2 secretion by chondrocytes. Furthermore, a highly purified IL 1-like factor, namely mononuclear cell factor (MCF) was also active on chondrocytes. The addition of highly purified IL 2 to rabbit chondrocytes had no effect on collagenase and PGE2 secretion induced by IL 1-containing media. Our findings suggest that the factor which induced collagenase and PGE2 secretion by rabbit chondrocytes was an IL 1-like factor. Thus, collagenase secretion by chondrocytes may be used as an IL 2-insensitive assay for the detection of IL 1-like factors.     

Specificities and sensitivities of four monoclonal antibodies for typing of Borrelia burgdorferi sensu lato isolates

Borrelia burgdorferi, the agent of Lyme borreliosis, is genetically more heterogeneous than previously thought. In Europe five genospecies have been described from the original B. burgdorferi sensu lato (sl): B. burgdorferi sensu stricto (ss), B. garinii, B. afzelii, B. lusitaniae, and B. valaisiana. In the United States, B. burgdorferi ss as well as B. bissettii in California and B. andersonii on the East Coast were differentiated. In Asia, B. japonica has been identified along, with B. garinii, B. afzelii, and B. valaisiana. In order to evaluate sensitivity and specificity of four species-specific monoclonal antibodies, we analyzed 210 B. burgdorferi sl isolates belonging to eight genospecies by immunoblot and confirmed genospecies by restriction fragment length polymorphism (RFLP) of rrf (5S)-rrl (23S) intergenic spacer amplicon. Monoclonal antibody H3TS had 100% sensitivity for 55 B. burgdorferi ss isolates but showed reactivity with all four isolates belonging to B. bissetii. Monoclonal antibody I 17.3 showed 100% specificity and sensitivity for 45 B. afzelii isolates. Monoclonal antibody D6 was 100% specific for B. garinii but missed 1 of 64 isolates (98.5% sensitivity). Monoclonal antibody A116k was 100% specific for B. valaisiana but was unreactive with 4 of 24 isolates (83.5% sensitivity). Genetic analysis correlated well with results of reactivity and confirmed efficacy of the phenotypic typing of these antibodies. Some isolates showed atypical RFLP. Therefore, both phenotypic and genotypic analyses are needed to characterize new Borrelia isolates.     

Modulation of endotoxic activity of lipopolysaccharide by high-density lipoprotein

Unlike agonists such as cytokines or hormones, the biological activity of bacterial lipopolysaccharide (LPS) is substantially modified by serum proteins. One such interaction in serum is with high-density lipoprotein (HDL) forming LPS-HDL complexes. LPS-HDL complexes have been previously shown to have reduced endotoxic activity, for example pyrogenicity, when compared to other forms of LPS in animal models. In this study, we report results of studies comparing the potency of LPS-HDL complexes with uncomplexed LPS as agonists for interleukin-1 (IL-1) production by two different sources of monocytes. LPS-HDL complexes were purified by ultracentrifugation in sodium bromide gradients. The human monocytic cell line THP-1 and the freshly isolated human monocytes, purified by adherence or elutriation from venous blood from healthy donors, were exposed to medium alone containing 1 mg/ml bovine serum albumin, HDL, LPS (parent LPS) and LPS-HDL complexes. mRNA level was analyzed on Northern blot, and cell-associated protein and supernatants were tested for IL-1 production using immunologic and biologic assays. LPS stimulates substantially more IL-1 mRNA and cell-associated IL-1 protein when the monocytes are stimulated with LPS alone versus LPS-HDL. These data suggest that LPS-HDL complexation may contribute to a reduction in endotoxic activities in vivo by preventing LPS (lipid A) from generating important transmembrane signals after binding to cells.