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Lisa Johnson
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E-mail: joh01715@umn.edu
Thesis Advisor: Steve
Jameson
Year entered: 2004
Degrees received:
B.S., Biology/Biotechnology, Carleton University, Ottawa,
Ontario, Canada 2000
Honors and Awards:
- MICaB Travel Award Spring 2009
Thesis research:
Memory CD8+ T cells can be generated in two distinct methods:
through antigen experience, or homeostatic proliferation.
Homeostatically proliferated cells are unique in that they
acquire a central memory phenotype without having experienced
cognate antigen. The positive signals that drive this process
are fairly well characterized (IL-7, IL-15, MHCI). My studies
have focused on restraints of homeostatic proliferation, namely
TGF-beta. We have found that cells that express a dominant
negative TGF-beta receptor II are less constrained than their
wild-type counterparts even in situations where lymphoid space,
and access to homeostatic cytokines is limited. These results
suggest a considerable role for TGF-? in the maintenance of
T cell homeostasis. The antigen driven response (using LM-OVA)
indicates that TGF-beta limits clonal expansion, but may be
required to memory cell formation, particularly secondary
memory. These two results contrast each other, indicating
the many roles that TGF-beta plays, depending on context.
Publications:
- Johnson, L.D.S. and Jameson S.C. Impaired TGF-? sensitivity
enhances lymphopenia-induced homeostatic proliferation but
not antigen driven responses of CD8+ T cells. Submitted.
- Haluszczak, C., A.D. Akue, S.E. Hamilton, L.D.S. Johnson
L. Pujanauski, L. Teodorovic, S.C. Jameson, and R.M. Kedl.
2009. The antigen-specific CD8+ T cell repertoire in unimmunized
mice includes memory phenotype cells bearing markers of
homeostatic expansion. Journal
of Experimental Medicine. 206: 435-448.
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