The immune system in the elderly: II. Specific cellular immunity.

Numerous changes occur in the immune system with advancing age, probably contributing to the decreased immunoresponsiveness in the elderly. These changes are often associated with important clinical manifestations such as increased susceptibility to infection and cancer frequently observed in the elderly population. Although both cellular and humoral immune responses are modified with advancing age, much of the decrease in immunoresponsiveness seen in elderly populations is associated with changes in T cell responses. The loss of effective immune activity is largely due to alterations within the T cell compartment which occur, in part, as a result of thymic involution. Substantial changes in both the functional and phenotypic profiles of T cells have been reported with advancing age. In fact, two prominent features of immunosenescence are altered T cell phenotype and reduced T cell response. One of the most consistent changes noted in T cells with advancing age is the decrease in the proportion of naive T cells with a concomitant increase in T cells with an activated/memory phenotype. In addition, there is evidence that the T cell population from aged individuals is hyporesponsive. The observed functional changes include decreased responsiveness to T cell receptor stimulation, impaired T cell proliferative capacity, a decline in the frequency of CD4+ T cells producing IL-2 and a decreased expression in IL-2 receptors. These latter findings probably explain the loss of proliferative capability of T cells from aged individuals. There is also evidence of a decrease in the early events of signal transduction, decreased activation-induced intracellular phosphorylation, and decreased cellular proliferative response to T cell receptor stimulation. The present review analyzes the main changes of the T cell compartment characterizing immunosenescence and discusses the possible mechanisms underlying these disregulations and their clinical implications.

The effects of primary division, student-mediated conflict resolution programs on playground aggression.

This study examined the effects of a student-mediated conflict resolution program on primary school (junior kindergarten to grade 5) playground aggression. Mediation teams of grade 5 students (approximately age 10) participated in 15 hours of training according to the model developed by Cunningham, Cunningham, and Martorelli (1997). Following baseline observations, mediation was introduced onto the playgrounds of three schools according to a multiple baseline design. Mediators successfully resolved approximately 90% of the playground conflicts in which they intervened. Direct observations suggest that the student mediation program reduced physically aggressive playground behavior by 51% to 65%. These effects were sustained at 1-year follow-up observations. Teacher and mediator satisfaction questionnaires provided strong support for impact, feasibility, and acceptability of this program.