The effect of counterion nature and concentration on phase transition, bilayer structure, vesicle size, vesicle internal volume per mole of amphiphile, and surface potential is evaluated for cationic vesicles composed of dioctadecyldimethylammonium (DODA) acetate, chloride, or bromide. Over a range of ionic strengths (0−5 mM monovalent salt), no interdigitation was detected in the bilayer structure for the three DODA counterions. The preferential type of aggregate formed from self-assembly of DODA salts is a large vesicle composed of a single traditional and noninterdigitated bilayer. Vesicle size and zeta-potentials were inversely related, i.e., an increase in zeta-potential was accompanied by a decrease in vesicle size. The largest zeta-potentials and smallest sizes were obtained for bilayer vesicles of DODA acetate which have the largest and more hydrated counterion. The effect of ionic strength (0−5 mM NaAc, NaCl, or NaBr as monovalent salt) was a slight decrease followed by a significant increase in vesicle size as a function of salt concentration. The results for counterion effects on vesicle size agree with predictions from the self-assembly model by Israelachvili and co-workers.

Nitric oxide (NO) is a free radical with pleiotropic functions. We have shown earlier that NO induces a population of CD4+CD25+Foxp3− regulatory T cells (NO-Tregs) which suppress the functions of CD4+CD25− effector T cells in vitro and in vivo. We report here an unexpected finding that NO-Tregs suppressed Th17 but not Th1 cell differentiation and function. In contrast, natural Tregs (nTregs), which suppressed Th1 cells, failed to suppress Th17 cells. Consistent with this observation, NO-Tregs inhibited the expression of RORγt but not T-bet, whereas nTregs suppressed T-bet, but not RORγt expression. The NO-Tregs-mediated suppression of Th17 was partially cell-contact-dependent and was associated with IL-10. In vivo, adoptively transferred NO-Tregs potently attenuated experimental autoimmune encephalomyelitis (EAE). The disease suppression was accompanied by a reduction of Th17, but not Th1 cells in the draining lymph nodes, and decrease in the production of IL-17, but increase in IL-10 synthesis. Our results therefore demonstrate the differential suppressive function between NO-Tregs and nTregs and indicate specialization of the regulatory mechanism of the immune system.

SUMMARYNestmate recognition studies, where a discriminator first recognises and then behaviourally discriminates (accepts/rejects) another individual, have used a variety of methodologies and contexts. This is potentially problematic because recognition errors in discrimination behaviour are predicted to be context-dependent. Here we compare the recognition decisions (accept/reject) of discriminators in two eusocial bees, Apis mellifera and Tetragonisca angustula, under different contexts. These contexts include natural guards at the hive entrance (control); natural guards held in plastic test arenas away from the hive entrance that vary either in the presence or absence of colony odour or the presence or absence of an additional nestmate discriminator; and, for the honey bee, the inside of the nest. For both honey bee and stingless bee guards, total recognition errors of behavioural discrimination made by guards (% nestmates rejected + % non-nestmates accepted) are much lower at the colony entrance (honey bee: 30.9%; stingless bee: 33.3%) than in the test arenas (honey bee: 60-86%; stingless bee: 61-81%; P<0.001 for both). Within the test arenas, the presence of colony odour specifically reduced the total recognition errors in honey bees, although this reduction still fell short of bringing error levels down to what was found at the colony entrance. Lastly, in honey bees, the data show that the in-nest collective behavioural discrimination by ca. 30 workers that contact an intruder is insufficient to achieve error-free recognition and is not as effective as the discrimination by guards at the entrance. Overall, these data demonstrate that context is a significant factor in a discriminators' ability to make appropriate recognition decisions, and should be considered when designing recognition study methodologies.