Innate Immune Responses in the Neutrophils of Community Dwelling and Nursing Home Elders

Abstract

Objective To evaluate innate immune responses of older disabled nursing home residents that may contribute to infectious disease susceptibility, we compared surface markers and signaling efficiency of neutrophils from nursing home residents and community dwelling elders. Design Observational pilot study. Setting Five New Haven, CT area nursing homes and the greater New Haven community. Participants 15 nursing home residents and 43 community dwelling elders. Measurements Neutrophils were isolated and Toll-like receptor (TLR) and β2 integrin expression on the surface of unstimulated neutrophils were measured via flow cytometry. Chemokine induction was determined by Quantitative PCR. Results Surface expression of TLR4 was elevated among nursing home residents compared to community dwellers (mean percent positive cells 33.91 [SE 2.75] vs. 15.67 [SE 1.58], p<0.001), while expression of the β2 integrins CD11b and CD18 was significantly lower (mean fluorescent intensity 460.8 [SE 49.1] vs. 632.9 [SE 29.5] for CD11b and 59.6 [SE 7.9] vs. 137.6 [SE 4.6] for CD18, p<0.0001). Neutrophils from nursing home residents produced substantially reduced levels of chemokines at baseline and after stimulation. Conclusions Because integrins are an important pathway to phagocyte signaling and contribute to adherence and locomotion of neutrophils, reduced β2 integrin expression may contribute to impaired responses to stimulation and reduced adhesive properties in PMN from nursing home residents. Since integrin CD11b has been shown to negatively regulate TLR4 response, it is plausible that lower levels of CD11b contribute to elevated expression of TLR4.

Reduced bioenergetics and toll-like receptor 1 function in human polymorphonuclear leukocytes in aging

“…We found that PMN from older donors express lower levels of TLR1 -- also noted on monocytes and dendritic cells [15, 18]-- which leads to reduced responses to TLR1 stimulation, reduced increases of adhesion molecules (integrins CD11b and CD18), and reduced production of the chemokine IL-8, mediated by reduced levels of activated p38 MAP kinase. Notably, these deficiencies are exacerbated in the frail elderly [32]. Although our study does not distinguish between whether the reduced expression of TLR1 alone accounts for the reduction in PMN function, or whether the remaining TLR1 may be impaired, lower efficiency of this critical pathway in aging is likely to play an important role in multiple PMN functions.…”

“…For stimulation assays, aliquots of whole blood were plated in 96-wells plate (180 μl/well) and incubated for 15 min in medium alone or with TNFα (20 ng/ml; R&D Systems, MN), or ligands for TLR 1 /2 (Pam3CSK4 5 μg/ml; Invivogen, CA), TLR2 (Pam2CSK4 1 μg/ml; Invivogen, CA), and TLR4 (LPS 0.5 μg/ml; Sigma, MO). Red blood cells were lysed and cell suspensions were labeled for 30 min at 4 °C with antibodies for PMN markers as follows: PE-CD11b, FITC-CD18, Pacific Blue-CD62L and V500-conjugated CD45 (BD Biosciences, CA) as described previously [32]. Data were acquired using an LSR II instrument (BD Biosciences, CA) and analyzed using FlowJo software (Tree Star, OR).…”

Frailty Is Associated With Neutrophil Dysfunction Which Is Correctable With Phosphoinositol-3-Kinase Inhibitors

“…The reduced systemic neutrophil proteinase activity in frailty alongside reduced migratory accuracy might suggest a double insult to cell function, impeding bacterial killing further. Although the previous investigation of frailty-associated immunosenescence is limited, systemic neutrophils isolated from frail older adults were shown to produce fewer chemokines than neutrophils from healthy older adults ( 21 ). This requires further study at baseline and following inflammatory challenges in vitro and in vivo to confirm this interpretation.…”

Immune senescence, epigenetics and autoimmunity

“…Aging affects both the adaptive and innate immunity systems [16, 17]. Neutrophils have a short lifespan and die by apoptosis if unstimulated, but pro-inflammatory stimuli such as lipopolysaccharide (LPS) can increase their lifespan [18, 19]. The number of neutrophils has been shown to be relatively high in the elderly with altered effector functions [20–22].…”