Effects of Age and Dietary β‐Carotene on Immunological Variables in Dogs

Abstract

␤-Carotene is a naturally occurring carotenoid reported to have health-promoting effects in several species. Advancing age is known to have a negative impact on various immune variables in several species. This study was conducted in order to assess the effect of age on immune response in dogs and to determine whether ␤-carotene is able to reverse this age-associated decline. To test this hypothesis, young and old dogs (n ϭ 36) were fed either a control diet or experimental diets containing supplemental ␤-carotene for 2-month periods. Age significantly (P Ͻ .05) lowered CD4ϩ T cell populations (47.2% versus 33.7%; young-control versus old-control, respectively) and ␤-carotene restored percent distributions in old dogs to nonsignificance versus younger controls (41.0%). T cell proliferation was lower in old dogs (30,254 Ϯ 2,248 versus 14,811 Ϯ 2,497 cCPM; young-control versus oldcontrol, respectively; P Ͻ .05), and ␤-carotene supplementation significantly improved responses in this age group (21,329 Ϯ 2,275 cCPM). Although B cell proliferation was depressed with age (17,967 Ϯ 1,384 versus 7,535 Ϯ 1,469 cCPM; young-control versus old-control, respectively; P Ͻ .05), ␤-carotene supplementation improved B cell proliferation in young dogs (23,500 Ϯ 1,339 cCPM). Old dogs displayed lower delayed-type hypersensitivity test (DTH) responses versus younger controls to both phytohemagglutinin-P (PHA; 11.1 Ϯ 0.95 versus 7.57 Ϯ 1.15 mm; young-control versus old-control, respectively; P Ͻ .05) and sheep red blood cell (RBC; 9.12 Ϯ 0.62 versus 8.08 Ϯ 0.75 mm; young-control versus old-control, respectively; P Ͻ .10). ␤-Carotene improved these responses, mostly within the first 24-48 hours after injection. In summary, older dogs have lower immunological responses compared with younger controls. ␤-Carotene supplementation significantly restored immune responses in older dogs when compared with their age-matched controls and younger counterparts.

Geriatrics

“…67 The results corroborated other work showing that both T-cell and B-cell populations in older dogs were reduced when compared with the populations of these cells in young adult dogs. 67 The results corroborated other work showing that both T-cell and B-cell populations in older dogs were reduced when compared with the populations of these cells in young adult dogs.…”

Multi-color flow cytometry for evaluating age-related changes in memory lymphocyte subsets in dogs

“…In humans, decreased T cell proliferation in the elderly is well documented, and has been associated with all-cause mortality(Effros and Walford, 1983; Ferguson et al, 1995; Jiang et al, 2007; Wayne et al, 1990). Several canine studies have also previously detected decreased lymphocyte proliferation in aged dogs although specific lymphocyte subsets were not assessed (Greeley et al, 2001; HogenEsch et al, 2004; Kearns et al, 1999; Massimino et al, 2003; Strasser et al, 2000). Notably, it has been suggested that these age-associated differences in lymphocyte function are a consequence of changes to the proportions of naïve and memory subsets that occur with age in humans; an explanation that would also explain our results in dogs(Ginaldi et al, 2001; Hoffmann et al, 2005).…”

“…Canine studies have determined that aged dogs display certain clinical characteristics of immunosenescence such as decreased antibody responses to novel pathogens and increased risk of cancers(Day, 2010; Fleming et al, 2011; Kearns et al, 1999; Kennedy et al, 2007). Corresponding evidence of decreasing immune function includes decreased proliferation of peripheral blood mononuclear cells (PBMCs), increased IFNγ expression by CD4+ T cells, and decreased proportions of CD45RA+ lymphocytes(Greeley et al, 2001; HogenEsch et al, 2004; Horiuchi et al, 2007; Massimino et al, 2003; Reis et al, 2005). Furthermore, a recent study showed that aged Labradors displayed a significant decrease in the number of clonal peaks in the locus encoding the T cell receptor (TCR) β chain variable region (TCRB V gene families) compared to young Labradors(Holder et al, 2018).…”

Pathogenic Phenotype and Genotype ofPseudomonas aeruginosaIsolates from Spontaneous Canine Ocular Infections

“…This finding may reflect age-related immunologic changes similar to those proposed for humans. The canine immune system undergoes a process of age-related compromise in function, with declines in leukocyte proliferation, mitogen stimulation, chemotaxis, phagocytosis, and various other immunologic parameters 36–38. These age-associated changes in immunity are similar between dogs and humans 39,40.…”