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Many immune functions decline with age and may jeopardize the elderly, as illustrated, for example by the significantly higher mortality rate from influenza in old age. Although innate and humoral immunity are affected by aging, it is the T cell compartment, which manifests most alterations. The mechanisms behind these alterations are still unclear, and several explanations have been offered including thymic involution and Telomere attrition leading to cell senescence. Age related accumulation of mutations has been documented and could serve as an additional mechanism of T cell dysfunction. One effective repair mechanism capable of rectifying errors in DNA replications is the mismatch repair (MMR) system. We previously reported a comparative examination of individual DNA samples from blood cells obtained at 10 year intervals from young and old subjects. We showed significantly higher rates of microsatellite instability (MSI), an indicator of MMR dysfunction in older subjects, compared to young. In the present study we confirm this result, using direct automated sequencing and in addition, we demonstrate that as CD8 lymphocytes from aged individuals, undergo repeated population doublings (PDs) in culture, they develop MSI. CD4 clones that also undergo repeated PDs in culture develop significant MSI as well. Elucidation of this previously unexplored facet of lymphocyte dynamics in relation to aging may help identify novel mechanisms of immunosenescence and pathways that could serve as targets for interventions to restore immune function. [Copyright &y& Elsevier]

Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL) have traditionally been considered as two distinct entities. However, there are rare reports of patients that, over time, develop both diseases. It remains unresolved whether the origin of the two diseases is from the same clone. In this study, we attempted to retrospectively investigate the clinical and molecular aspects of patients who developed both lymphomas. The rearranged immunoglobulin heavy-chain variable region genes from both diagnoses were compared to each other. Twenty-six patients presented with both diagnoses. Twelve had HL as the primary disorder (“HL first” group) and the majority of these (75%) presented with aggressive lymphoma as the second lymphoma. In contrast, in the 11 patients for whom NHL was the primary disorder (“NHL first” group), this was usually (82%) of low-grade histology. Three patients were diagnosed concurrently with both diseases. Mean age at first diagnosis was higher (p = 0.037) in the NHL first group (56.1 years) than in the HL first group (40 years). Mean time between diagnoses was longer (p = 0.026) in the HL first group (9 years) than in the NHL first group (5 years). For 11 patients, diagnostic samples were available for molecular analyses from both diagnoses of HL and NHL. In 6 of these 11 patients, gene rearrangement studies were informative. No patient had the same gene rearrangement identified in both diseases. It seems that development of HL and NHL in one patient, at different time points, reflects, in many cases, separate biologic diseases. [Copyright &y& Elsevier]