Mechanisms for Decreased Function of B Cells in Aged Mice and Humans

Abstract The immune system has been known for some time to be compromised in aged individuals, e.g., both mice and humans, and in both humoral and cellular responses. Our studies have begun to elucidate intrinsic B lymphocyte defects in Ig class switch recombination, activation-induced cytidine deaminase, and E47 transcription factor expression. These defects occur in both mice and humans. Our studies have also shown that tristetraprolin is one of the key players in regulating the decreased E47 mRNA stability in aged B lymphocytes. These and current studies should lead to improvements in B lymphocyte function in aged populations

Allogeneic Mesenchymal Stem Cells as a Treatment for Aging Frailty

As life expectancy is projected to increase in the ensuing decades, individuals of older age continue to exceed the previous generation’s lifespan. Advancing age is associated with a reduction in physical and mental functional capacity, and chronic inflammation is a major factor contributing to this decline. A heightened inflammatory state can lead to exhaustion, weakness, weight loss, slow gate speed, and an overall decrease in activity level. These phenotypes define the onset of the disease process known as frailty. Frailty is a growing epidemic, which severely undermines a person’s ability to deal with outside stressors, and increases their rate of hospitalization, institutionalization, and mortality. Current interventions focus on preventative care by improving exercise capacity, strength, nutritional supplementation, diet, and mobility. However, a biological cure has heretofore remained elusive. Here, we introduce the novel therapeutic principle that mesenchymal stem cell (MSC) therapy may represent a safe, practical, and efficacious both the treatment and prevention of frailty in individuals of advancing age. To date, a phase I safety trial reveals an excellent safety profile and suggests that mesenchymal stem cells can ameliorate signs and symptoms of frailty. These early studies lay the groundwork for future large-scale clinical trials of this exciting and novel therapeutic concept that has the potential to expand health span in the aging population

Liposome-mediated transfection of mature taste cells

The introduction and expression of exogenous DNA in neurons is valuable for analyzing a range of cellular and molecular processes in the periphery, e.g., the roles of transduction-related proteins, the impact of growth factors on development and differentiation, and the function of promoters specific to cell type. However, sensory receptor cells, particularly chemosensory cells, have been difficult to transfect. We have successfully introduced plasmids expressing green and Discosoma Red fluorescent proteins (GFP and DsRed) into rat taste buds in primary culture. Transfection efficiency increased when delaminated taste epithelium was redigested with fresh protease, suggesting that a protective barrier of extracellular matrix surrounding taste cells may normally be present. Because taste buds are heterogeneous aggregates of cells, we used alpha-gustducin, neuronal cell adhesion molecule (NCAM), and neuronal ubiquitin carboxyl terminal hydrolase (PGP9.5), markers for defined subsets of mature taste cells, to demonstrate that liposome-mediated transfection targets multiple taste cell types. After testing eight commercially available lipids, we identified one, Transfast, that is most effective on taste cells. We also demonstrate the effectiveness of two common "promiscuous" promoters and one promoter that taste cells use endogenously. These studies should permit ex vivo strategies for studying development and cellular function in taste cells

Mechanisms for Decreased Function of B Cells in Aged Mice and Humans

The immune system has been known for some time to be compromised in aged individuals, e.g., both mice and humans, and in both humoral and cellular responses. Our studies have begun to elucidate intrinsic B lymphocyte defects in Ig class switch recombination, activation-induced cytidine deaminase, and E47 transcription factor expression. These defects occur in both mice and humans. Our studies have also shown that tristetraprolin is one of the key players in regulating the decreased E47 mRNA stability in aged B lymphocytes. These and current studies should lead to improvements in B lymphocyte function in aged populations

Intrinsic defects in B cell response to influenza vaccination in elderly humans (84.11)

Abstract We have previously shown that elderly humans have fewer percentages of CD19+ total B cells, switch memory B cells, and increased percentages of naïve B cells. Activated CD19+ B cells have less E47, AID and Igγ1 circle transcripts (CTs) with age. AID is critical for class switch recombination (CSR) and somatic hypermutation, both necessary for optimal function of immunoglobulin (Ig). More recently we have initiated a series of experiments to measure the antibody response to influenza vaccination by hemagglutination inhibition assay (HI) and associated this with the isolated/intrinsic B cell response to these antigens (containing adjuvants) in vitro. Our results show that the specific in vitro AID response of B cells to vaccination and the in vivo serum HI response to vaccination are both decreased with age. We are currently pursuing these studies with more subjects and with both seasonal as well as H1N1 vaccine response. These results indicate that these biomarkers (decreased E47, AID, CSR, IgG) could more accurately track optimal immune responses and activity, and would be better predictors of vaccine and therapeutic agent effectiveness in humans

Age effects on B cells and humoral immunity in humans

Both humoral and cellular immune responses are impaired in aged individuals, leading to decreased vaccine responses. Although T cell defects occur, defects in B cells play a significant role in age-related humoral immune changes. The ability to undergo class switch recombination (CSR), the enzyme for CSR, AID (activation-induced cytidine deaminase) and the transcription factor E47 are all decreased in aged stimulated B cells. We here present an overview of age-related changes in human B cell markers and functions, and also discuss some controversies in the field of B cell aging

Pax5 and E47 regulate AID and class switch recombination in young and aged BALB/c mice (84.6)

Abstract Our laboratory has shown that stimulated B cells from senescent mice (19 to 24 months) have an intrinsic defect in class switch recombination (CSR) that is coincident with reduced E47. In aging, the decrease in E47 correlates proportionally with levels of activation induced cytidine deaminase (Aicda/AID) transcripts; but, other transcription factors may be involved. Pax5 has been shown to play a role in CSR. The purpose of the present study was to determine whether 1) Pax5 is decreased with age, 2) the decrease in Pax5 correlates with decreased CSR in aged B cells, 3) increased E47 and/or Pax5 can rescue the decreased CSR observed in these cells and 4) depletion of Pax5 down-regulates E47 and/or AID expression. Here, we demonstrate that E47 and Pax5 are both down-regulated in mature splenic B cells of aged mice. Endogenous E47, Pax5 and IgG1 are increased in old as well as young primary stimulated B cells in response to exogenously expressed E47. We successfully rescued levels of both E47 and Pax5 mRNA and protein in transduced splenic B cells of aged mice when compared to young untransduced controls. Restoration of Pax5 expression increased E47, AID and CSR in B cells from aged mice. Conversely, silencing Pax5 by means of siRNA transfection decreased E47 and AID expression significantly. These results suggest a possible feedback mechanism between E47 and Pax5. Our results show that E47 and Pax5 cooperate to regulate AID and CSR in both young and old B lymphocytes