title: Effect of plasma lipoproteins on natural killer cell activity in the elderly population.
abstract: BACKGROUND
  Natural killer (NK) cells possess spontaneous cytotoxicity against tumors and virus-infected cells to play a major role in immunosurveillance and defense against the development of cancer, as well as bacterial and viral infections. The role of plasma lipoproteins in atherogenesis is well recognized, but the physiological relevance of their immunoregulatory properties is still questioned. In particular, it is unknown whether hypercholesterolemia should be considered a risk factor for diminished immunity in old age.
  
  
  METHODS
  To evaluate effects of plasma lipoprotein levels on immune function, we assessed the relation between plasma lipoprotein profiles and NK cell activity. NK cell activity was assayed by release of (51)Cr from K562 target cells, and concurrent plasma lipoprotein levels were measured in 47 samples of elderly males (mean age +/- SD, 66.6 +/- 1.7 years).
  
  
  RESULTS
  Univariate regression analyses revealed direct relations between NK cell activity and high-density lipoprotein cholesterol (r=.46, p<.001), apolipoprotein (Apo) A-1 (r=.48, p<.001), and Apo A-2 (r=.46, p<.005). In addition, multiple regression analyses showed a direct independent relation between NK cell activity and Apo A-1 (b=0.32+/-0.09 mg/dl, beta=0.48, and p <.001).
  
  
  CONCLUSIONS
  NK cell activity is related directly to plasma Apo A-1 levels in elderly subjects. The mechanisms of this interaction are unknown, but Apo A-1 contributes to the composition of the antiatherogenic fraction of high-density lipoprotein and could also defend against infectious and malignant disease through a potential for NK cell activity.
authors.affiliation: First Department of Medical Technology, School of Health Sciences. Second Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan.
authors.forename: Tomiya
authors.initials: T
authors.lastname: Yasumasu
authors.forename: Kazuo
authors.initials: K
authors.lastname: Takahara
authors.forename: Takao
authors.initials: T
authors.lastname: Sadayasu
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Date
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Isozumi
authors.forename: Ryouji
authors.initials: R
authors.lastname: Kouzuma
authors.forename: Yasuhide
authors.initials: Y
authors.lastname: Nakashima
mesh_terms: D000368:Aged; D000886:Anthropometry; D006801:Humans; D007694:Killer Cells, Natural / Q000276:immunology / Q000502:physiology*; D008074:Lipoproteins / Q000097:blood / Q000276:immunology / Q000502:physiology*; D008297:Male; D012044:Regression Analysis
chemical_list: D008074:Lipoproteins