A Study of Serum Immunoglobulin Levels in Elderly Persons That Provides New Insights into B Cell Immunosenescence

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Abstract
Abstract:  The literature on immunosenescence has focused mainly on T cell impairment. With the aim of gaining insight into B cell immunosenescence, we investigated the serum immunoglobulin levels in a cohort of 166 subjects (20–106 years). Serum IgG (and IgG subclasses) were quantified by the nephelometric technique, IgE by CAP system fluorescence enzyme immunoassay, and IgD by radial immunodiffusion (RID). There was an age‐related increase of IgG and IgA; the IgG age‐related increase was significant only in men, but IgG1 levels showed an age‐related increase both in men and women, whereas IgG3 showed an age‐related increase only in men. IgE levels remain unchanged, whereas IgD and IgM serum levels decreased with age; the IgM age‐related decrease was significant only in women, likely due to the relatively small sample of aged men. Thus, in the elderly the B cell repertoire available to respond to new antigenic challenge is decreased. A lot of memory IgD− B cells are filling immunological space and the amount of naïve IgD+ B cells is dramatically decreased. This shift away from a population of predominantly naïve B cells obviously reflects the influences of cumulative exposure to foreign pathogens over time. These age‐dependent B cell changes indicate that advanced age is a condition characterized by lack of clonotypic immune response to new extracellular pathogens. In any event, the increase of memory B cells and the loss of naïve B cells, as measured by serum IgD levels, could represent hallmarks of immunosenescence and could provide useful biomarkers possibly related to the life span of humans.

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