Being in a crowd bonds people via physiological synchrony.

Collective events can generate intense emotions, shape group identities, and forge strong bonds. Do these effects extend to remote participation, and what are the psychological mechanisms underpinning their social power? We monitored psycho-physiological activity among groups of basketball fans who either attended games in-person (in a stadium) or watched games live on television in small groups. In-person attendance was associated with greater synchronicity in autonomic nervous system activation at the group level, which resulted in more transformative experiences and contributed to stronger identity fusion. Our findings suggest that the social effects of sports depend substantially on the inter-personal dynamics unfolding among fans, rather than being prompted simply by watching the game itself. Given the increasing prevalence of virtual experiences, this has potentially wide-reaching implications for many domains of collective human interaction.

Interplay between order-parameter and system parameter dynamics: considerations on perceptual-cognitive-behavioral mode-mode transitions exhibiting positive and negative hysteresis and on response times.

A mathematical model is presented for the emergence of perceptual-cognitive-behavioral modes in psychophysical experiments in which participants are confronted with two alternatives. The model is based on the theory of self-organization and, in particular, the order parameter concept such that the emergence of a mode is conceptualized as an instability leading to the emergence of an appropriately defined order parameter. The order parameter model is merged with a second model that describes adaptation in terms of a system parameter dynamics. It is shown that the two-component model predicts hysteretic mode-mode transitions when control parameters are increased or decreased beyond critical values. The two-component model can account for both positive and negative hysteresis effects due to the interaction between order parameter and system parameter dynamics. Moreover, the model-based analysis reveals that response time curves look rather flat when response times are relatively decoupled from the mode-mode transition phenomenon. In general, response time curves exhibit a peaked close to the mode-mode transition point. In this context, the possibility is discussed that such peaked response time curves belong to the class of critical phenomena of self-organizing systems. In order to illustrate the relevance of peaked response time curves for future research and research reported in the past, results from a perceptual judgment experiment are reported, in which participants judged their ability to stand on a tilted slope for various angles of inclination. Response time curves were found that exhibited a peak around the mode-mode-transition points between "yes" and "no" responses.

CD50 and CD62L adhesion receptor expression on naive (CD45RA+) and memory (CD45RO+) T lymphocytes in the elderly.

A complex reshaping characterizes cellular immunity in the elderly. In particular, the hallmark of the "senescence" of the T cell compartment is a decrease in the proportion of CD45RA+ naive T lymphocytes concomitantly with an expansion of CD45RO+ memory T cells. However, in addition to age-dependent changes in their representation, phenotypical and functional anomalies also characterize naive and memory T cell populations in the elderly. Since cell adhesion molecules (CAMs) are multifunctional receptors which play important roles not only in cell-to-cell and cell-to-matrix interactions but also in signal transduction and cell activation, we analysed, by means of a three-colour flow cytometry method, the proportion, absolute number and density expression or mean fluorescence intensity (MFI) of CD50 (ICAM-3) and CD62L (L-selectin homing receptor) adhesion receptors on CD45RA+ and CD45RO+ peripheral blood CD3+ T cell subsets from 10 healthy elderly subjects and 10 young controls. Our aim was to investigate age-dependent changes in the expression pattern of these CAMs on naive and memory lymphocytes which might contribute to the remodelling of the immune system in the elderly. We considered the mean values +/- standard deviations of the percentage, absolute number and MFI of positive cells. The percentage of naive T cells expressing CD50 was not significantly modified in aged (94.8 +/- 5.0%) compared to young individuals (97.8 +/- 3.2%). On the contrary, the percentage of memory T cells exhibiting CD50 was lower in elderly than young donors (92.0 +/- 6.4 vs. 98.3 +/- 2.2%; p < 0.01). The percentage of naive T cells expressing CD62L was decreased in the elderly donors (53.3 +/- 18.8 vs. 80.8 +/- 11.0%; p < 0.001), whereas the proportion of CD62L+ memory T lymphocytes was substantially comparable between the two age groups (63.5 +/- 15.7 vs. 54.7 +/- 12.3%). The absolute number per mm(3) of CD50+ naive T cells from aged individuals was decreased (251.9 +/- 141.9 vs. 621.8 +/- 238.0/mm(3); p < 0.001), whereas memory peripheral blood T lymphocytes expressing CD50 were substantially unchanged (863.8 +/- 260.9 vs. 802.7 +/- 139.6/mm(3)). On the contrary, the absolute numbers per mm(3) of naive and memory peripheral blood T lymphocytes exhibiting CD62L were respectively decreased (190.8 +/- 133.4/mm(3)) and increased (515.1 +/- 146.8/mm(3)) in elderly donors compared to young controls (601.3 +/- 129.1 and 351.8 +/- 195.0/mm(3); p < 0.001 and p < 0.05, respectively). Finally, CD50 MFI values of naive as well as memory T cell subpopulations from aged subjects were increased compared to young donors (14.0 +/- 2.0 vs. 9.8 +/- 1.2 and 14.0 +/- 2.0 vs. 11.6 +/- 1.3; p < 0.001 and p < 0.01, respectively). CD62L was also overexpressed in both naive (8.4 +/- 1.6 vs. 6.7 +/- 1.4; p < 0.05) and memory (10.3 +/- 2.5 vs. 5.4 +/- 1.1; p < 0.001) T subsets in the elderly. CD50 and CD62L upregulation could be interpreted as a compensatory mechanism for a decreased responsiveness and a greater requirement for activation signals rather than an age-related anomaly.

Activated naive and memory CD4+ and CD8+ subsets in different stages of HIV infection.

The aim of this study was to evaluate the changes and the correlations between the main lymphoid phenotypes indicative of activation and/or functional states during the course of HIV infection. Immunophenotype studies by flow cytometry were performed on blood samples from 59 HIV-1-positive patients, divided into four stages, and 18 seronegative healthy controls, to determine the expression of HLA-DR, CD29 and CD45RA on CD4+ and CD8+ lymphocytes. HLA-DR expression was elevated on the total lymphocyte population and in both the main T subsets. Its presence on CD4+ lymphocytes probably has a different significance in the first phase of infection when it is indicative of reactive activation, in contrast to the more advanced stages of disease when it favors the spread of HIV infection among this cellular subset. The increasing state of immune activation is also confirmed by a proportional decrease in the expression of CD45RA, substantial stability of CD29 and an increase in double-negative CD4+ cells as the infection proceeds. Also CD8+HLA-DR+ lymphocytes increase during the course of disease. The parallel increase of the CD8+CD45RA+ subset in asymptomatic patients suggests the presence in this phase of infection of peripheral blood immature and activated CD8+ cells. Similarly to CD4+, the CD29 subset of CD8+ lymphocytes remains unchanged compared to controls during disease progression. In both CD4+ and CD8+ subsets we observed the increase of a double-negative sub-population of uncertain significance. HLA-DR, the memory marker CD29 and the naive marker CD45RA seem to be the more promising and helpful indicators for a better staging of disease and may provide information that accurately correlates with progression of infection. The peculiar trend of the described phenotypic alterations could represent changes in the immune response to HIV during disease progression and facilitate the definition of specific immune patterns in different stages of HIV infection.

Tuftsin deficiency in AIDS.

Tuftsin is an endogenous tetrapeptide that stimulates phagocytosis and is released from the Fc fragment of IgG by a splenic endocarboxypeptidase. Tuftsin activity and splenic function were measured in 21 patients with AIDS, 7 patients with AIDS-related complex (ARC), 22 patients who had undergone splenectomy, and 37 healthy volunteers. There was a significant inverse correlation between tuftsin activity and splenic function in all subjects. Tuftsin activity was significantly lower in patients with AIDS, ARC, and in those who had undergone splenectomy compared with healthy volunteers. Tuftsin deficiency may contribute to the risk of bacterial infection in symptomatic HIV-positive individuals.