AUTHOR=Moro-García Marco A., Alonso-Arias Rebeca , Lopez-Larrea Carlos 

TITLE=When Aging Reaches CD4+ T-Cells: Phenotypic and Functional Changes

JOURNAL=Frontiers in Immunology

VOLUME=4

YEAR=2013

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2013.00107

DOI=10.3389/fimmu.2013.00107

ISSN=1664-3224

ABSTRACT=<p>Beyond midlife, the immune system shows aging features and its defensive capability becomes impaired, by a process known as immunosenescence that involves many changes in the innate and adaptive responses. Innate immunity seems to be better preserved globally, while the adaptive immune response exhibits profound age-dependent modifications. Elderly people display a decline in numbers of naïve T-cells in peripheral blood and lymphoid tissues, while, in contrast, their proportion of highly differentiated effector and memory T-cells, such as the CD28<sup>null</sup> T-cells, increases markedly. Naïve and memory CD4+ T-cells constitute a highly dynamic system with constant homeostatic and antigen-driven proliferation, influx, and loss of T-cells. Thymic activity dwindles with age and essentially ceases in the later decades of life, severely constraining the generation of new T-cells. Homeostatic control mechanisms are very effective at maintaining a large and diverse subset of naïve CD4+ T-cells throughout life, but although later than in CD8 + T-cell compartment, these mechanisms ultimately fail with age.</p>