Journals of Gerontology Series A: Biological Sciences and Medical Sciences, Vol 50, Issue 4 M227-M233, Copyright © 1995 by The Gerontological Society of America
Variations in activity of the human natural anti-Gal antibody in young and elderly populations
L Wang, F Anaraki, TR Henion and U Galili
Department of Microbiology and Immunology, Medical College of Pennsylvania, Philadelphia, USA.
BACKGROUND. Anti-Gal is a natural antibody which constitutes approximately
1% of circulating IgG in humans and which interacts specifically with the
mammalian carbohydrate epitope Gal alpha 1-3Gal beta 1-4GlcNAc-R (termed
the alpha-galactosyl epitope). The purpose of this study was to determine
whether there are age-associated changes in the affinity of anti-Gal in
elderly individuals. METHODS. The age- associated variations in affinity of
anti-Gal were determined by the extent of this antibody binding to
solid-phase alpha-galactosyl epitopes (mouse laminin) in ELISA, performed
at various serum dilutions with serum samples from 140 elderly and 127
young individuals. The data were expressed as the mean of optical density
(O.D.) values measured at serum dilutions of 1:40, 1:80, and 1:160, and
correlated with the affinity of anti-Gal as measured in equilibrium
dialysis. RESULTS. The proportion of individuals with low-affinity anti-Gal
is sixfold higher in the elderly than in the young population. Whereas
low-affinity binding of anti-Gal (mean O.D. value < or = 1.0) was
observed in only 6% of the young population, as many as 35% of the elderly
population displayed such low-affinity anti-Gal. Anti-Gal affinity in ELISA
assay correlated with the affinity of this antibody as measured in
equilibrium dialysis. CONCLUSION. The proportion of individuals with low
affinity anti-Gal increases in the elderly population in comparison with
the young population. The possible molecular mechanisms which may result in
the age-associated decrease in the antibody affinity are discussed.
