Aged humans and experimental animals have a poor immune response to infectious agents and vaccines. The antibody-mediated humoral immune response is qualitatively deficient in aged individuals with the production of antibodies of lower affinity and with self reactivity. Although problems with T cells certainly contribute to these B cell deficits in aging, intrinsic B cell changes are shown in this proposal. The ability to switch immunoglobulin (Ig) heavy chain class (isotype) is critical for proper effector functions of the Ig protein and genetic defects in the ability of humans to undergo class switch recombination (CSR) result in immunodeficiency with increased susceptibility to many pathogens. These studies will focus on the molecular and cellular mechanisms responsible for the decrease in Ig class switch in aged mice. We hypothesize that the decrease in CSR is a direct result of a decrease in the activation-induced cytidine deaminase, AID, which in turn is regulated by a decrease in the transcription factor, E47, in aged mice. This proposal will compare splenic B cells from aged vs. young mice for the presence and function of E47, AID and class switched isotypes (IgG, IgE, IgA) in vitro as well as in antigen-specific responses in vivo.
In Specific Aim 1 we will extend preliminary data to establish the intrinsic splenic B cell defect in Ig class switch in aged BALB/c, C57BL/6 and E2A+/- mice. Purified splenic B cells will be activated with mitogens or anti-CD40 and various cytokines and class switch measured by ELISA for secreted Ig, fluorescent cytometry for cell surface Ig molecularly by detection of germ line transcripts (GLT) and post-switch transcripts (PST). In vivo experiments with immunization with NP-KLH or NP-Ficoll (thymus-dependent and thymus-independent antigens) and adoptive transfer of combinations of young and old B/T cells into SCID mice will be done.
In Specific Aim 2, the molecular mechanisms regulating class switch in young and old mice will be investigated. E47, Id2, Notch, NFicB and AID expression in aged B cells will be characterized. Experiments will include chromatin immunoprecipitation (ChIP) with anti-E2A (for the AID gene) as well as attempts to rescue class switch in aged B cells with retroviral transduction of AID or E47.
hi Specific Aim 3, the molecular mechanisms for regulation of E47 and AID will be established. Studies of protein and mRNA stability, post translational regulation, and signal transduction pathways including MAPK, will determine key molecular elements in the control of Ig class switch in aged mice.

National Institute of Health (NIH)
National Institute on Aging (NIA)
Method to Extend Research in Time (MERIT) Award (R37)
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Special Emphasis Panel (NSS)
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Fuldner, Rebecca A
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University of Miami School of Medicine
Schools of Medicine
Coral Gables
United States
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Frasca, Daniela; Blomberg, Bonnie B (2016) Inflammaging decreases adaptive and innate immune responses in mice and humans. Biogerontology 17:7-19
Ratliff, Michelle; Alter, Sarah; McAvoy, Kelly et al. (2015) In aged mice, low surrogate light chain promotes pro-B-cell apoptotic resistance, compromises the PreBCR checkpoint, and favors generation of autoreactive, phosphorylcholine-specific B cells. Aging Cell 14:382-90
Frasca, Daniela; Blomberg, Bonnie B (2014) B cell function and influenza vaccine responses in healthy aging and disease. Curr Opin Immunol 29:112-8
Ratliff, Michelle; Alter, Sarah; Frasca, Daniela et al. (2013) In senescence, age-associated B cells secrete TNFα and inhibit survival of B-cell precursors. Aging Cell 12:303-11
Khurana, Surender; Frasca, Daniela; Blomberg, Bonnie et al. (2012) AID activity in B cells strongly correlates with polyclonal antibody affinity maturation in-vivo following pandemic 2009-H1N1 vaccination in humans. PLoS Pathog 8:e1002920
Frasca, Daniela; Romero, Maria; Diaz, Alain et al. (2012) A molecular mechanism for TNF-α-mediated downregulation of B cell responses. J Immunol 188:279-86
Frasca, Daniela; Diaz, Alain; Romero, Maria et al. (2011) Age effects on B cells and humoral immunity in humans. Ageing Res Rev 10:330-5
Landin, Ana M; Frasca, Daniela; Harrison, Patrick et al. (2011) E47 retroviral rescue of intrinsic B-cell defects in senescent mice. Aging Cell 10:327-37
Blomberg, Bonnie B; Frasca, Daniela (2011) Quantity, not quality, of antibody response decreased in the elderly. J Clin Invest 121:2981-3
Frasca, Daniela; Diaz, Alain; Romero, Maria et al. (2010) Intrinsic defects in B cell response to seasonal influenza vaccination in elderly humans. Vaccine 28:8077-84

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