Effect of aging on CD11b and CD69 surface expression by vesicular insertion in human polymorphonuclear leucocytes

Abstract

The exocytosis of intracellular vesicles is an important function of the plasma membrane, which is responsible for hormone secretion, cell surface expression of antigens, ion transporters and receptors, and intracellular and intercellular signalling. Human aging is associated with many physiological and cellular changes, many of which are due to alterations in plasma membrane functioning. Alterations in vesicle externalization with age could account for many of these changes. We investigated whether alterations in vesicle exocytosis occur with increasing age by flow-cytometric determination of CD11b and CD69 expression on the surface of human polymorphonuclear leucocytes (PMN) stimulated with phorbol myristate acetate (PMA), a tumour promoter which binds to and activates protein kinase C (PKC) directly, or with formyl-Met-Leu-Phe (fMLP), which activates PKC indirectly via interactions with a cell surface receptor and G-protein, and subsequent inositol phosphate hydrolysis. Following stimulation with PMA, a decrease in the proportion of PMN expressing CD69 at high levels was observed in elderly compared with young subjects (young, 55.3%; elderly, 43.9%; P=0.01). No aging-related differences in the proportion of PMN expressing CD11b (young, 73.7%; elderly, 68.4%; P=0.15), or in the number of molecules of CD69 or CD11b expressed per cell, were observed. Stimulation with fMLP or low PMA concentrations resulted in full CD11b expression but minimal CD69 expression in both young and elderly subjects. Cells which expressed CD69 had no CD11b expression, while those cells expressing CD11b had minimal CD69 expression. Thus the PMA-induced expression of CD11b and CD69 in human PMN represents two separate processes, only one of which is affected in aging. CD11b expression appears to require a lesser degree of PKC stimulation compared with that required for CD69 expression. The age-associated reduction in PMA-stimulated CD69 expression may occur either at or distal to PKC activation. Such a decrease may contribute to the age-associated impairments in PMN function that contribute, in turn, to immunosenescence.

Neutrophil antigen exposure is altered with age in relatives of patients with Type 2 diabetes

“…between BMI-SDS at diagnosis and age of diagnosis [5]. We have not shown a negative correlation in our population, despite adequate power in our cohort of white children (80% power to detect r=0.33).…”

“…Cellular fluorescence was measured by flow cytometry. Neutrophils were identified from a mixed leukocyte population according to their light-scatter properties and their surface expression of CD45 as described previously [5]. Flow cytometry data were analysed using WinMDI version 2.8.…”

“…Using density gradient centrifugation according to the method described by Sanchez Quesada [5], six LDL subfractions were isolated [1,2,3,4,5,6] from lesser to greater density: LDL1 (1.020-1.026 g/ml), LDL2 (1.026-1.030 g/ml), LDL3 (1.030-1.036 g/ml), LDL4 (1.036-1.043 g/ml), LDL5 (1.043-1.051 g/ml), LDL6 (1.051-1.056 g/ml). Plasma lipase activity was measured according to a previous study [6].…”

Physiologic variations in granulocytic surface antigen expression: impact of age, gender, pregnancy, race, and stress

“…Inconsistent results of CD11b expression have also been encountered in pregnant women and elderly individuals. CD11b expression has been reported to be normal or increased in these populations [7,9,10,[22][23][24][25][26]. However, pregnant women delivering prematurely have consistently shown a higher expression of CD11b [27].…”

Phenotypic and functional changes of circulating monocytes and polymorphonuclear leucocytes from elderly persons

“…A significant expansion of CD14dim CD16bright subpopulation of circulating monocytes in elderly subjects, that may indicate a state of in vivo activation, has been also demonstrated 8 . The flow cytometric analysis of cell surface marker expression in PMN displayed a higher level of CD11b and CD15, mediating an increase in neutrophil adhesion with endothelial cells and platelets 9 , 10 , 11 . Other authors 3 demonstrated a reduced expression of CD16 on neutrophils from elderly donors which clearly contributes to a decreased phagocytosis.…”