Immunobiography and the Heterogeneity of Immune Responses in the Elderly: A Focus on Inflammaging and Trained Immunity.

open6noFunding. This work has been partially supported by the European Union (EU)’s H2020 Project “Propag-ageing” (grant agreement no. 634821) to CF and PG; EU JPND “Adage” to CF; EU FP7 “HUMAN”: Health and the understanding of Metabolism, Aging and Nutrition (grant agreement no. 602757) to CF; University of Bologna FARB linea 2 Project 2014 no. RFBO120790 to MC; and CARIPLO (Fondazione Cassa di Risparmio delle Province Lombarde)—2016-0835 Ricerca malattie invecchiamento 2016 to ME.https://www.frontiersin.org/articles/10.3389/fimmu.2017.00982/fullOwing to its memory and plasticity, the immune system (IS) is capable of recording all the immunological experiences and stimuli it was exposed to. The combination of type, dose, intensity, and temporal sequence of antigenic stimuli that each individual is exposed to has been named “immunobiography.” This immunological history induces a lifelong continuous adaptation of the IS, which is responsible for the capability to mount strong, weak or no response to specific antigens, thus determining the large heterogeneity of immunological responses. In the last years, it is becoming clear that memory is not solely a feature of adaptive immunity, as it has been observed that also innate immune cells are provided with a sort of memory, dubbed “trained immunity.” In this review, we discuss the main characteristics of trained immunity as a possible contributor to inflammaging within the perspective of immunobiography, with particular attention to the phenotypic changes of the cell populations known to be involved in trained immunity. In conclusion, immunobiography emerges as a pervasive and comprehensive concept that could help in understanding and interpret the individual heterogeneity of immune responses (to infections and vaccinations) that becomes particularly evident at old age and could affect immunosenescence and inflammaging.openFranceschi, C; Salvioli, S; Garagnani, P; de Eguileor, M; Monti, D; Capri, M.Franceschi, C; Salvioli, S; Garagnani, P; de Eguileor, M; Monti, D; Capri, M