Project: Research project

Project Details


In senescence, B lymphopoiesis declines dramatically. In the mouse,
decreased production of pre-B cells in the bone marrow is accompanied
by alterations in the generation of the B cell specificity repertoire.
Such disfunction in B cell repertoire expression has been shown to
adversely affect protective murine humoral immunity to infectious
microorganisms. The molecular mechanisms responsible for the diminished
B lymphopoiesis during aging have not been addressed. We hypothesize
that I) with senescence, mice express significantly lower levels o the
enzymes Rag-1/2 and terminal deoxynucleotidyl transferase (TdT); 2)
this results in altered Vh gene usage and diminished N segment
diversity and leads to production of mu heavy chain V region sequences
which are less effective in combining with surrogate light chains
(lambda5; VpreB) and/or fail to produce functional pre-B cell
receptors; and 3) as a result, fewer new pre-B cells are recruited into
the mitotically active large pre-B cell stage. The consequences of
these events would be both diminished numbers of small, resting pre-B
cells within the bone marrow and alteration of the Vh repertoire seen
at the pre-B cell level. In order to test this hypothesis, we propose
in Specific Aim 1 to evaluate expression of Rag- 1/2, and TdT within
cell sorted pro-B and pre-B cells at both the protein and mRNA levels
as a function of age. In Specific Aim 2, the expression of mu heavy
chain and surrogate light chain expression in pro-B and pre-B cells
from young and senescent mice will be compared. Finally, in Specific
Aim 3, CDR3 Vh sequences for two gene families, Vh36-60 and Vh7183,
will be amplified from genomic DNA by PCR, cloned, and sequenced. The
expression of these VII genes as productive and non-productive
rearrangements will be determined among nascent (CD43+ CD25+ B220+) and
later (CD43- CD25+ B220+) pre-B cells from young and aged mice. These
studies will provide insight into the effect of aging on the VII-
dependent recruitment/proliferation apparent among pre-B cells.
Completion of these Specific Aims will provide a molecular
understanding of the events which underlie the progressive loss of B
lymphopoiesis and alterations in repertoire expression seen during
Effective start/end date8/1/977/31/99


  • National Institute on Aging


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