Interplay between telomere length and telomerase in human leukocyte differentiation and aging

Blood leukocytes derive from bone marrow hematopoietic stem cells and differentiate into multiple types of mature cells that include granulocytes, monocytes, mast cells of myeloid lineage, and T and B lymphocytes of lymphoid lineage. Their distinctive paths of differentiation and unique roles in immune response provide a model for comparative analysis of biological parameters, such as telomere length and telomerase activity, in different types of leukocytes. Age has also been associated with the decline in immune functions and with the attrition of telomere length in leukocytes. This review will summarize recent progress in the study of telomere length and telomerase expression in leukocytes during differentiation and aging. In addition, I will attempt to shed new light on the roles of telomere and telomerase in leukocyte function and potential clinical interventions.