T cell activation through the Ag receptor (TCR) requires sustained signaling from signalosomes within lipid raft microdomains in the plasma membrane. In a proteomic analysis of lipid rafts from human T cells, we identified stomatin-like protein (SLP)-2 as a candidate molecule involved in T cell activation through the Ag receptor. In this study, we show that SLP-2 expression in human primary lymphocytes is up-regulated following in vivo and ex vivo activation. In activated T cells, SLP-2 interacts with components of TCR signalosomes and with polymerized actin. More importantly, up-regulation of SLP-2 expression in human T cell lines and primary peripheral blood T cells increases effector responses, whereas down-regulation of SLP-2 expression correlates with loss of sustained TCR signaling and decreased T cell activation. Our data suggest that SLP-2 is an important player in T cell activation by ensuring sustained TCR signaling, which is required for full effector T cell differentiation, and point to SLP-2 as a potential target for immunomodulation.

Weaning mass in southern elephant seals is highly variable, the heaviest pups being three times as heavy as the lightest ones. After weaning, pups undergo an extensive postweaning period in which they draw on their reserves. To quantify the energy expenditure during the postweaning period, changes in mass, body composition, and postweaning duration were measured in southern elephant seals at King George Island, South Shetland Islands, Antarctica. Overall, mean pup weaning mass was 154 +/- 26 kg (n=117) and did not differ between sexes. Mean minimum postweaning duration was 42.5 +/- 7.5 d. Heavier animals at weaning had lower mass-specific mass loss rates than lighter ones, and a faster depletion of body reserves was associated with a shorter postweaning period. The proportion of body mass represented by fat at weaning was 37% +/- 4% (n=47) and did not differ between sexes. Of these pups, 36 were recaptured after a mean period of 36 d after weaning. On average, total mass loss measured in these animals (39 kg) was composed of 39% water, 47% fat, and 12% protein. The composition of mass loss was not significantly different between sexes and was not related to weaning mass or total body energy reserves. However, fatter animals at weaning lost more fat per kilogram lost than thinner ones. Late in the fast, males and females appeared to be in a similar body condition. Nevertheless, the overall proportion of body mass represented by fat at this time was lower than that presented by the same animals at weaning. We estimated that during the postweaning period pups lost, on average, 30% of their mass at weaning. This comprised approximately 35% of the energy and 32% of the fat in the pup's body.

Our results support the use of autologous MSC transplanted as MSC/CM/PRP for the treatment of nonunion fractures. Future studies incorporating a larger number of patients may confirm the results obtained in this work.

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