AGE-RELATED IMBALANCE OF VIRGIN (CD45RA+) AND MEMORY (CD45R0+) CELLS BETWEEN CD4+ AND CD8+ LYMPHOCYTES-T IN HUMANS - A STUDY FROM NEWBORNS TO CENTENARIANS

The expression of CD45RA and CD45R0 isoforms of the leukocyte common antigen - characteristic of virgin and memory T cells, respectively - has been studied by three colour cytofluorimetric analysis on CD4+ or CD8+ peripheral blood CD3+ cells from 131 healthy donors 0-106 years old. As expected, at birth 95-99% of the CD3+ lymphocytes expressed CD45RA isoform. A rapid increase of CD45R0+ cells was observed in the first 2-3 decades of life, this phenomenon being much more pronounced on CD4+ cells. Subsequently, the increase of the memory compartment was much less rapid. After the tenth decade of life a consistent reservoire of CD45RA+ among CD4+ cells was still present (about 20%). At this advanced age the percentage of virgin cells among CD8+ T lymphocytes was even higher (about 50%), and only slightly lower than that of young donors (about 55-60%). The significance of the age-related unbalance in the proportion of virgin and memory cells between CD4+ and CD8+ T lymphocytes is unknown. The presence of a great number of virgin T lymphocytes within the CD4+ and the CD8+ T cell subsets even in the peripheral blood of centenarians poses the problem of their origin (thymus? extrathymic sites?) and their functional role.