Research Interests
Salmonella Project - The Effect of Vaccine Strain SL3235 on the Murine
Immune Response
During the past several years my undergraduate biology students and
I have been involved in an ongoing research project. This work is
devoted to an understanding of the immune response to a vaccine strain
of Salmonella typhimurium (SL3235). We have examined the lymph
node and splenic profile of both B and T lymphocytes to strain SL3235.
This work was performed using flow cytometry and required that the students
be both trained and work at the University of Pennsylvania flow cytometry
center. The accompanying photomicrograph is of mouse (C3HeB/FeJ strain)
B lymphocytes stained with an anti mouse IgG antibody conjugated
to FITC. The results of those experiments suggested the current round
of experiments into the cytokine (white blood cell hormone) response of
mice exposed to the vaccine strain of Salmonella. Data already collected
suggests an early gamma interferon response and an early but prolonged
interleukin 4 response. Experiments performed recently demonstrate
a very early (2-6 hours post inoculation) interleukn 12p40 (IL12p40)
response to the vaccine strain of Salmonella. Interleukin 12 is a
proinflammatory mediator produced by antigen presenting cells (macrophage,
B cells and dendritic cells). Interleukin 12 is thought to drive
the immune response towards the cell mediated arm. This is in keeping
with the ability of Salmonella typhimurium to multiply with macrophage.
These results give us insight into the direction the immune system takes
after exposure to the vaccine strain of Salmonella. It suggests that
an early gamma interferon response is necessary to prime the immune system
for a later cellular immune response. It also suggests the the gamma
interferon response itself is stimulated by the early IL12 production.
This is in keeping with other recently published data. Additional
experiments are needed to confirm and expand the results we already have
on the cytokine response. A better understanding of the cytokine
response can lead to development of a better Salmonella vaccine.
We hope to contribute to the worldwide effort on development of an effective
vaccine to typhoid fever.
Amphibian Decline Project - Role of Environmental Stress on Natural Resistance
and Immune Response in Ranid Amphibians
Herpetologists world-wide have noticed a precipitous decrease in the
number of amphibians in all geographical areas of the world. This
concern has been the subject of several international symposia held within
the last several years ( National Research Council (NRC), 1990).
It is also the subject of an international newsletter, entitled FrogLog.
FrogLog is the newsletter of the Declining Amphibian Populations Task Force.
I was recently asked to submit an account of my work in this area, much
of which has been funded by Widener University Faculty Development Grants.
This piece appeared in the January 1997 issue of FrogLog.
The general conclusion reached at these meetings and in FrogLog
is that the observed declines in amphibian population were so widespread
and sudden that it could not be explained solely as the result of coincidental
natural population fluctuation (Wake, 1991, but see Pechman et al. 1991).
Several anthropogenic causes were proposed to explain these declines including
global climate change, acid rain, increased ultraviolet light radiation,
pollution by biocides and habitat destruction (Wake, 1991).
Frogs are extremely sensitive to their aquatic environment due to the
extreme permeability of their skin (Duellman and Trueb, 1988; Simon, 1984).
Poor water quality could therefore have an adverse impact on adult frogs
found in water during breeding season. Acidification of freshwater
habitats due to anthropogenic-caused acid precipitation may contribute
significantly to a harmful aquatic environment (McDonald et al. 1984).
Some studies have dealt with examining mechanisms that could explain the
cause of acidification induced mortality in amphibian species. Our work
has focused on the effect that acidification has on ranid mortality (the
leopard frog Rana pipiens) ,the immune system and particularly the
phagocytic function of white blood cells.
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