Social status in mice: behavioral, endocrine and immune changes are context dependent.

The aim of the present study was to investigate the effect of social status on the endocrine, immune and behavior response of male mice. We found that in mice reared in a group of siblings since weaning, no difference exists between dominants and subordinates in basal corticosterone level, in behavior in the open-field test (OFT) and in a series of immune parameters. These results suggest that living with siblings is not a stressful condition for either dominant or subordinate mice. Therefore, group-housed siblings can be regarded as a valid control group in social stress studies. When mice were subjected to chronic psychosocial stress for 21 days, four types of social outcome occurred: residents becoming dominants, intruders becoming subordinates, residents becoming subordinates and intruders becoming dominants. Interestingly, the behavioral profile in the OFT revealed a status-dependent effect, with resident dominants (RD) and intruder dominants (InD) showing the highest locomotor and exploratory activity, whereas the corticosterone level was higher than control for all four categories. In addition, a context-dependent effect emerged at the immune level: resident subordinates (RS) had a reduced splenocyte proliferation and IL-4 and IL-10 production. Mice in all the other three social ranks showed no immune alterations. Therefore, the loss of an individual's social rank position seems a promising field of study to investigate the psychological impact of stressful events.

Selective induction of interleukin-12 in reconstructed human epidermis by chemical allergens.

Keratinocytes play an important role in skin inflammatory and immunological reactions through the release of cytokines and response to them. These cells have been shown to direct T-cell priming by producing cytokines such as interleukin (IL)-10 and IL-12. The purpose of this work was to explore the potential use of IL-12 production to discriminate between skin irritants and contact allergens in vitro. Initially, a reconstituted human epidermis was treated with a known human skin irritant, sodium lauryl sulphate (SLS), and a known human contact allergen, 1-chloro-2,4-dinitrobenzene (DNCB). The expression of IL-12p40 was assessed at specific time intervals by the semi-quantitative reverse transcriptase-polymerase chain reaction (rt-PCR). The data obtained indicated that only DNCB induced an up-regulation of IL-12p40. This up-regulation occurred after exposure to DNCB for 3 hours. Importantly, the application of SLS or vehicles did not induce IL-12 mRNA up-regulation. An increase in total IL-12 protein content was detected in supernatants of allergen-stimulated, but not vehicle-stimulated, reconstituted epidermis. To confirm these results, the effects of benzalkonium chloride, oxazolone and eugenol were assessed. At concentrations that resulted in equivalent IL-1α release, only contact allergens increased IL-12 expression, which confirmed the previous results. These data suggest that IL-12, which is crucial for T-helper type 1 cell responses, could be a useful marker for discriminating between contact allergens and irritants.