A double-negative (IgD CD27 ) B cell population is increased in the peripheraludblood of elderly people

摘要

The T cell branch of the immune system has been extensively studied in the elderly and it is known thatudthe elderly have impaired immune function, mainly due to the chronic antigenic load that ultimatelyudcauses shrinkage of the T cell repertoire and filling of the immunologic space with memory T cells. In theudpresent paper,we describe the IgD CD27 double-negative B cell population which (aswe have recentlyuddescribed) is higher in the elderly. Most of these cells were IgG+. Evaluation of the telomere length andudexpression of the ABCB1 transporter and anti-apoptotic molecule, Bcl2, shows that they have theudmarkers of memory B cells. We also show that these cells do not act as antigen presenting cells, asudindicated by the low levels of CD80 and DR, nor do they express significant levels of the CD40 moleculeudnecessary to interact with T lymphocytes through the ligand, CD154. Hence, we hypothesize that theseudexpanded cells are late memory or exhausted cells that have down-modulated the expression of CD27udand filled the immunologic space in the elderly. These cells might be the age-related manifestation ofudtime-enduring stimulation or dysregulation of the immune system.