Richard Riley, Ph.D.

Professor of Microbiology and Immunology
Room 727, McKnight Building
1638 NW 10 Avenue
Telephone: 305-243-2644
Lab: 305-243-6075
Fax: 305-243-8595
Email: rriley@med.miami.edu

Research Interests:

REGULATION OF B LYMPHOCYTE DEVELOPMENT AND FUNCTION IN SENESCENCE.

The focus of our research is to understand the regulatory mechanisms governing the formation of antibody-producing B lymphocytes. In particular, we seek to determine the effects of senescence ("old age") upon B lymphocyte formation and function and the ramifications of abnormal B lymphocyte development upon immune competence. This is of importance since elderly individuals often exhibit compromised immunity to pathogens, respond poorly to vaccination, and show increased autoimmunity. Our goal is to determine how altered mechanisms of lymphocyte formation and function impact immune competence in old age.

Dysregulation of B Lymphocyte Development in Senescence

Normal mice exhibit reduced development of B lymphocytes in senescence (“old age”) and decreased antibody-mediated immunity. Our research indicates that, in senescent mice, the production of B lymphocytes is abnormally regulated at a precise developmental stage: the pre-B cell. We have observed a decline in the expression of molecules critical to the establishment of pre-B cells, including the surrogate light chains which comprise the pre-B cell receptor. Newly formed pre-B cells express pre-B cell receptor (pBCR) molecules at the cell surface. These pBCR molecules are comprised of the immunoglobulin m heavy chain together with surrogate light chain proteins gamma5 and VpreB. Signaling via the pBCR promotes survival and proliferation of the new pre-B cell. In aged mice, production of surrogate light chains is reduced, presumably affecting pBCR expression and/or function. This, in turn, may result in decreased production of pre-B cells and B cells. In addition to defects affecting pre-B cell survival and expansion, we have also described defects in the function of earlier B cell precursors (pro-B cells) in senescence. In particular, this involves diminished responses to the growth/survival cytokine IL-7. Our goals in this project are to determine the mechanisms, both B lineage cell intrinsic and microenvironmental, which alter the growth and survival properties of early and late (pro-B/pre-B) B lineage precursors within the bone marrow.

Dysregulation of B-Lineage Transcription Factors in Senescence

The expression and function of key transcriptional regulators effectively "program" the development of B cell precursors within the bone marrow. These include the basic helix-loop-helix E2A proteins as well as Early B cell Factor (EBF) and Pax-5 which encodes B cell Specific Activating Protein (BSAP). These operate in a hierarchial manner, e.g., E2A > EBF > Pax-5. We have reported that E2A expression and function is reduced in early B cell precursors from senescent mice; Pax-5/BSAP expression is similarly reduced. This may contribute to the poor formation and maintenance of B cell precursors in aged mice. While the mechanisms responsible for these alterations are under study, we have shown that regulation of these molecules includes posttranslational controls on protein turnover. This is mediated primarily via the ubiquitin-proteasome pathway. In aged B cell precursors, this pathway results in increased degradation and turnover of E2A and Pax-5/BSAP and lower steady-state levels of these crucial transcription factors. Further research is currently directed to dissecting the molecular events which alter the ubiquitin-proteasome pathway in aged B cell precursors with particular attention focused on the effects of Notch. The alterations in handling of molecules key to B lineage "programming" during senescence may result from cell intrinsic changes or to changes in the senescent bone marrow microenvironment. Studies are in progress to distinguish among these possibilities.ns alters pre-B cell function.

Alterations in New B Cell Formation and "Read-out" of the B Cell Antibody Repertoire in Senescence

As B cell precursor numbers decline in the bone marrow of aged mice, the production of new B cells also is reduced. While this may impair the formation of all new B cells randomly, without regard to B cell specificity, our results suggest the opposite alternative, e.g., that pre-B cells are reduced in a non-random manner with subsequent "skewed" formation of new B cells. This is based, in part, on the specificity of their B cell Ig receptors. We have reported that new B cells within the bone marrow are heterogeneous in phenotype, Ig repertoire, and survival capability. In aged mice, while formation of the majority of new B cell specificities is impaired, maintenance of a subset of new B cells exhibiting a "selected" B cell specificity repertoire is observed. The implications of this "Ig repertoire reshaping" in old age to the capacity of B cells to populate follicular, marginal zone, and B1 compartments and to participate in protective responses to pathogens is currently under study.

Significance

Study of the regulation of B lymphocyte development during senescence will provide new insights into processes controlling B lymphocyte differentiation. Furthermore, understanding the mechanisms altering B lymphocyte development may suggest therapeutic treatments useful for minimizing the immune abnormalities seen in senescent individuals.

Selected Publications:

Van Der Put, E., Frasca, D., King, A.M., Blomberg, B.B., and Riley, R.L. 2004. Decreased E47 in senescent B cell precursors is stage specific and regulated posttranslationally by protein turnover. J.Immunol.173: 818-827.

Frasca, D., Van Der Put, E., Riley, R.L., and Blomberg, B.B. 2004. Effects of aging on DNA-binding activity of the E47 transcription factor in splenic B cells. Mech. Aging Dev. 125: 111-112.

Frasca, D., Van Der Put, E., Riley, R.L., and Blomberg, B.B. 2004. Age-related differences in the E2A-encoded transcription factor E47 in bone marrow derived B cell precursors and in splenic B cells. Exp. Gerontology 39: 481-489.

Frasca, D., Van Der Put, E., Riley, R.L., and Blomberg, B.B. 2004. Reduced Ig class switch in aged mice correlates with decreased E47 and activation induced cytidine deaminase. J.Immunol. 172: 2155-2162.

Wilson, E.L., Sherwood, E.M., King, A.M., and Riley, R.L. 2003. A phenotypically distinct subset of bone marrow immature B cells exhibits partial activation, increased survival, and preferential expression of VhS107. Eur.J.Immunol. 33: 3498-3506.

Van Der Put, E., Sherwood, E.M., Blomberg, B.B., and Riley, R.L. 2003. Aged mice exhibit distinct B cell precursor phenotypes differing in activation, proliferation, and apoptosis. Exp. Gerontology 10: 1137-1147.

Frasca, D., Nguyen, D., Van Der Put, E., Riley, R.L., and Blomberg, B.B. 2003. The age related decrease in E47 DNA binding does not depend on increased Id inhibitory proteins in bone marrow derived B cell precursors. Frontiers in Bioscience 8: A110-116.

Frasca, D., Nguyen, D., Riley, R.L., and Blomberg, B.B. 2003. Effects of aging on proliferation and E47 transcription factor activity induced by different stimuli in murine splenic B cells. Mech. Ageing Dev. 124: 361-369. 

Sherwood, E.M., Xu, W., and Riley, R.L. 2003. B cell precursors in senescent mice exhibit decreased recruitment into proliferative compartments and altered expression of Bcl-2 family members. Mech. Ageing and Development 124: 147-153.

Frasca, D., Nguyen, D., Riley, R.L., and Blomberg, B.B. 2003. Decreased E12 and/or E47 transcription factor activity in the bone marrow as well as in the spleen of aged mice. J. Immunol. 170: 719-726.

Riley, R.L., Knowles, J., and King, A.M. 2002. Levels of E2A protein expression in B cell precursors are stage-dependent and inhibited by stem cell factor (c-kit ligand). Experimental Hematology 30: 1412-1418.

Sherwood, E.M., Xu, W., King, A.M., Blomberg, B.B., and Riley, R.L. 2000. The reduced expression of surrogate light chains in B cell precursors from senescent BALB/c mice is associated with decreased E2A proteins. Mech Ageing Dev. 2000 Sep 1;118(1-2):45-59.

Donohoe, M.E., Beck-Engesser, G., Lonberg, N., Karasuyama, H., Riley, R.L., Jack, H-M., and Blomberg, B.B. 2000. Transgenic human lambda5 rescues the murine nullizygous phenotype. J. Immunol. 164: 5269-5276.

Sherwood, E.M., Blomberg, B.B., Xu, W., Warner, C.A., and Riley, R.L. 1998. Cutting Edge: Senescent BALB/c mice exhibit decreased expression of lambda 5 surrogate light chains and reduced development within the pre-B cell compartment. J. Immunol. 161: 4472-4475.

Sherwood, E.M., Blomberg, B.B., Xu, W., Warner, C.A. and Riley, R.L. 1998. Senescent BALB/c mice exhibit decreased expression of lambda5 surrogate light chains and reduced development with the pre-B cell compartment. J. Immunol. 161:4472-4475.

Adkins, B. and Riley, R.L. 1998. Autoantibodies to T-lineage cells in aged mice. Mech. Ageing Dev. 103:147-164.