non_disease
Unbiased pyrosequencing of human immunoglobulin mRNA repertoires defines onset of immune senescence
The adaptive immune system protects from foreign and potentially dangerous antigens by generating specific antibody responses. The vast variety of immunoglobulin (Ig) paratopes for antigen recognition is a result of a V(D)J recombination mechanism1 while a fast and efficient immune response is mediated by specific immunoglobulin isotypes obtained through class switch recombination2. Analysis of antibody repertoires has been revolutionized with the introduction of Next Generation Sequencing (NGS) technologies and provides insight into the nature of antibody diversity in a yet unrivalled depth.  However, in depth analysis of immune diversity in antibody repertoires of a healthy donor cohort representing different age groups has yet not been performed due to lack of appropriate methods. Rather, previous sequencing studies focused on specific problems covering only fractions of the Ig-repertoire.   Through unbiased monitoring of the V(D)J recombination pattern interrelated with Ig-isotypes on mRNA level using pyrosequencing, we now show an age-dependent reduction of class switch capability. We observed a comparable overall diversity and usage in V(D)J recombination pattern in 14 healthy donors irrespective of age and gender. When all five isotypes including subtypes were analysed, age dependent differences became apparent. In elderly (>50), the relative number of IgM and IgD transcripts as well as their VDJ variability increases. At the same time, the overall transcript number of class-switched isotypes and their variability decreases. Comparison of the most frequently occurring VDJ recombination patterns within isotypes of the individual donors separates young adults from elderly and could be correlated with age on a global level. Our observation is in concordance with findings that specific disease neutralizing IgG can be found in elderly donors with reduced amounts12, provides a feasible explanation for reduced vaccination efficacy reported in the elderly population13 and suggests that not VDJ recombination ability itself but rather class-switch efficiency and Ig-expression is constrained with age. We conclude that the age of fifty defines the onset of immune senescence in humans and propose that elderly specific vaccination strategies should include the golden-agers.