Anergy and not clonal ignorance determines the fate of B cells that recognize a physiological autoantigen

Autoantibodies to insulin arise spontaneously in the insulin autoimmune syndrome and in type I diabetes. In addition, administration of insulin to individuals without autoimmune disease routinely results in Abs that bind autologous hormone. These observations and findings in transgenic models of tolerance led to an inference that physiological levels of hormones and growth factors, such as insulin, are not sufficient to induce tolerance in B cells, a state termed clonal ignorance. In contrast, we have discovered that virtually all conventional B cells expressing a low affinity anti-insulin transgene interact with endogenous insulin and are effectively silenced for Ig production and for T cell-dependent immune responses. A fraction of transgenic B cells escapes silencing and functions autonomously to produce insulin Abs that may lower fasting blood sugars similar to an insulin autoimmune syndrome. These B cells have characteristics of a B1-like subset and are depleted by hypotonic peritoneal lysis. These findings question the concept of clonal ignorance and show that physiological concentrations of Ag may effectively silence conventional B cells even when the affinity for autoantigen is low. Self-reactivity may arise in the repertoire because of compartmental differences that govern the fate of B cells and not as a result of true clonal ignorance.     

Cytologically based physical maps of the group-2 chromosomes of wheat

We have constructed cytologically based physical maps (CBPMs), depicting the chromosomal distribution of RFLP markers, of the group-2 chromosomes of common wheat (Triticum aestivum L. em Thell). Twenty-one homozygous deletion lines for 2A, 2B, and 2D were used to allocate RFLP loci to 19 deletion-interval regions. A consensus CBPM was colinearily aligned with a consensus genetic map of group-2 chromosomes. The comparison revealed greater frequency of recombination in the distal regions. Several molecularly tagged chromosome regions were identified which may be within the resolving power of pulsed-field gel electrophoresis. The CBPMs show that the available probes completely mark the group-2 chromosomes, and landmark loci for sub-arm regions were identified for targeted-mapping.     

A cyanobacterial system for consolidation of phosphate slimes

Dilute aqueous suspensions of finely divided mineral waste from phosphate ore beneficiation were allowed to consolidate in the presence of either Anacystis nidulans or Anabaena cylindrica. Addition to this mineral suspension of 2.2 mg (dry weight) of fresh A. nidulans per milliliter of suspension resulted in solids consolidation that exceeded the untreated control by 65% after 11 days. When fresh A. cylindrica was mixed with the slimes suspension, no enhancement of consolidation occurred. Addition of either 1 mgof dry A. nidulans or 1 mg of dry A. cylindrica per milliliter of suspension resulted in consolidation that exceeded the untreated control by 25% after 9 days. Direct addition of A. nidulans to the process water of facilities relying on gravitational dewatering of such mineral suspensions could reduce the residence time in the initial settling ponds. Whether such a process would affect long‐term settling is unknown.     

Mesencephalic dopaminergic neurons express a repertoire of olfactory receptors and respond to odorant-like molecules

Background

The mesencephalic dopaminergic (mDA) cell system is composed of two major groups of projecting cells in the Substantia Nigra (SN) (A9 neurons) and the Ventral Tegmental Area (VTA) (A10 cells). Selective degeneration of A9 neurons occurs in Parkinson’s disease (PD) while abnormal function of A10 cells has been linked to schizophrenia, attention deficit and addiction. The molecular basis that underlies selective vulnerability of A9 and A10 neurons is presently unknown.

Results

By taking advantage of transgenic labeling, laser capture microdissection coupled to nano Cap-Analysis of Gene Expression (nanoCAGE) technology on isolated A9 and A10 cells, we found that a subset of Olfactory Receptors (OR)s is expressed in mDA neurons. Gene expression analysis was integrated with the FANTOM5 Helicos CAGE sequencing datasets, showing the presence of these ORs in selected tissues and brain areas outside of the olfactory epithelium. OR expression in the mesencephalon was validated by RT-PCR and in situ hybridization. By screening 16 potential ligands on 5 mDA ORs recombinantly expressed in an heterologous in vitro system, we identified carvone enantiomers as agonists at Olfr287 and able to evoke an intracellular Ca²⁺ increase in solitary mDA neurons. ORs were found expressed in human SN and down-regulated in PD post mortem brains.

Conclusions

Our study indicates that mDA neurons express ORs and respond to odor-like molecules providing new opportunities for pharmacological intervention in disease.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-729) contains supplementary material, which is available to authorized users.     

In vitro assessment of some sperm function following exposure to levonorgestrel in human fallopian tubes

Background  

The mechanism of action of levonorgestrel (LNG) as emergency contraception (EC) remains a subject of debate and its effect on sperm function has been only partially explained. The aim of this study was to assess whether LNG at a similar dose to those found in serum following oral intake for EC could affect spermatozoa when exposed to human fallopian tubes in vitro.