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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No Study Section (in-house review) (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; Diaz, Alain; Romero, Maria et al. (2017) Obesity induces pro-inflammatory B cells and impairs B cell function in old mice. Mech Ageing Dev 162:91-99
Diaz, Alain; Romero, Maria; Vazquez, Thomas et al. (2017) Metformin improves in vivo and in vitro B cell function in individuals with obesity and Type-2 Diabetes. Vaccine 35:2694-2700
Frasca, Daniela; Blomberg, Bonnie B (2017) Adipose Tissue Inflammation Induces B Cell Inflammation and Decreases B Cell Function in Aging. Front Immunol 8:1003
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Frasca, D; Diaz, A; Romero, M et al. (2017) Ageing and obesity similarly impair antibody responses. Clin Exp Immunol 187:64-70
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Frasca, Daniela; Blomberg, Bonnie B (2016) Aging, cytomegalovirus (CMV) and influenza vaccine responses. Hum Vaccin Immunother 12:682-90
Frasca, Daniela; Blomberg, Bonnie B (2016) B Cell-Specific Biomarkers for Optimal Antibody Responses to Influenza Vaccination and Molecular Pathways That Reduce B Cell Function with Aging. Crit Rev Immunol 36:523-537
Frasca, Daniela; Ferracci, Franco; Diaz, Alain et al. (2016) Obesity decreases B cell responses in young and elderly individuals. Obesity (Silver Spring) 24:615-25

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