The document discusses the susceptibility of NC/Nga mice to Listeria monocytogenes (LM) infection compared to other mouse strains. Figure 2 shows that NC/Nga mice have decreasing levels of the protective cytokine IFN-γ and increasing levels of the anti-inflammatory cytokine IL-10 after LM infection. This suggests high IL-10 levels may explain the mice's susceptibility. However, Figures 3 and 4 appear to contradict this, so more research is needed to understand IL-10's role in listeriosis.

1. ｱﾊﾞｵﾗﾘｰﾈﾙﾋﾞﾙﾊﾞｵ February 26, 2010
Infection Immunology 川本先生
Why is NC/Nga Mice Highly-Susceptible to LM Infection
In the lecture that was presented on the Function of Immune Responses Against
Infection last January 27, 2010, we were asked about our hypothesis on the role of
Interleukin (IL)-10 in Listeriosis. Before I discussed the figures given, I would like to
define some important terms of the report.
According to Wikipedia, Listeria monocytogenes (LM) is a facultative intracellular
bacterium that is the causative agent of Listeriosis. It is one of the most virulent food
borne pathogens with twenty (20) to thirty (30) percent of clinical infections resulting
in death. Responsible for approximately 2,500 illnesses and 500 deaths in the
United States (U.S.) annually, listeriosis is the leading cause of death among food
borne bacterial pathogens with fatality rates exceeding even Salmonella and
Clostridium botulinum.
LM is a Gram-positive bacterium, in the division Firmicutes, named for Joseph Lister.
Motile via flagella at 30 °C and below but usually not at 37 °C, LM can instead move
within eukaryotic cells by explosive polymerization of actin filaments (known as
comet tails or actin rockets). Studies suggest that up to 10% of human
gastrointestinal tracts may be colonized by LM.1 Nevertheless, clinical diseases due
to LM are more frequently recognized by veterinarians, especially as meningo-
encephalitis in ruminants. More recently, LM has been used as the model organism
to illustrate the patho-biotechnology concept.
Meanwhile, Wikipedia defined Interferon-gamma (IFN-γ) as a dimerized soluble
cytokine that is the only member of the type II class of interferons. This interferon
was originally called macrophage-activating factor, a term now used to describe a
larger family of proteins to which IFN-γ belongs. IFN-γ, or type II interferon, functions
as a cytokine that is critical for innate and adaptive immunity against viral and
intracellular bacterial infections and for tumor control. Aberrant IFN-γ expression is
associated with a number of auto inflammatory and autoimmune diseases. The
importance of IFN-γ in the immune system stems in part from its ability to inhibit viral
replication directly, but, most important, derives from its immunostimulatory and
immunomodulatory effects. IFN-γ is produced predominantly by natural killer (NK)
and natural killer T (NKT) cells as part of the innate immune response, and by CD4
and CD8 cytotoxic T lymphocyte (CTL) effector T cells once antigen-specific
immunity develops.
And lastly, Interleukin-10 (IL-10), also known as human cytokine synthesis inhibitory
factor (CSIF), is known as an anti-inflammatory cytokine. This cytokine is produced
primarily by monocytes and to a lesser extent by lymphocytes. This cytokine has
pleiotropic effects in immunoregulation and inflammation. It down-regulates the
expression of Th1 cytokines, MHC class II antigens, and costimulatory molecules on
macrophages. It also enhances B cell survival, proliferation, and antibody
production.
1
Ramaswamy, Vidhya and Cresence, Vincent Mary. "Listeria - Review of Epidemiology and
Pathogenesis." J Microbiol Immunol Infect. (2007). 40:4-13
1

2. This cytokine can block NF-κB activity, and is involved in the regulation of the JAK-
STAT signaling pathway. Knockout studies in mice suggested the function of this
cytokine as an essential immunoregulator in the intestinal tract.2
A study in mice has shown that interleukin-10 is also produced by mast cells,
counteracting the inflammatory effect that these cells have at the site of an allergic
reaction.3 It is capable of inhibiting synthesis of pro-inflammatory cytokines like IFN-
γ, IL-2, IL-3, TNFα and GM-CSF made by cells such as macrophages and the Type 1
T helper cells. IL-10 also displays potent abilities to suppress the antigen
presentation capacity of antigen presenting cells. However, it is also stimulatory
towards certain T cells, mast cells and stimulates B cell maturation and antibody
production.
In Figure 1, a dose of LM 8.0 x 105 was administered per head to the NC/Nga, BALB/
c, and C57BL/6 mice. It can be seen that until day 3 post infection, the three (3) mice
have a survival rate of 100%. However, by day 4 post infection, the survival rate of
the NC/Nga mice went down to around 10%. And finally, by day 5 post infection,
there were no more survivors in the NC/Nga mice (unlike in the BALB/c mice and
C57BL/6 mice). In the day 5 post infection, BALB/c mice had a survival rate of 80%
while C57BL/6 mice, 100%.
Figure 1. NC/Nga Mice is Highly Susceptible to LM Infection
2
"Entrez Gene: IL10 interleukin 10"
3
Grimbaldeston, MA, et. al. (October 2007). "Mast cell-derived interleukin 10 limits skin pathology in
contact dermatitis and chronic irradiation with ultraviolet B". Nat. Immunol. 8 (10): 1095–104.
2

3. In the case of Figure 2, the IFN-γ level in NC/Nga mice increased to around 13,000
during the day 1 post infection. However, it decreased to around 12,000 during the
day 2 post infection. And finally, it further decreased to 11,000 during the day 3 post
infection. After day 3 post infection, there was no more data on IFN-γ as the NC/Nga
Mice have died. This may lead to a hypothesis that the IFN-γ is important to the
survival rate of NC/Nga Mice being subjected to Listeriosis.
The analysis for the role of IL-10 is the opposite of that of the IFN-γ. The serum level
of IL-10 for NC/Nga mice is at 500 during the day 1 post infection. It increased to
around 600 serum levels during the day 2 post infection. Then, it shot up to the
3,000 level by day 3 post infection. However, by day 4 post infection, all the NC/Nga
mice have died. It seems that the presence of significantly high serum levels of IL-10
is detrimental to the survival rate of NC/Nga mice.
Figure 2. Increased serum levels of IL-10 in NC/Nga Mice
The results of IL-10 in Figure 1 are consistent with the results of a similar study on
the Role of IL-10 in a Neonatal Mouse Listeriosis Model that was done in 1999. This
study was undertaken to test the hypothesis that altered IL-10 production plays a role
in the increased susceptibility of neonates to listeriosis. 4 Plasma IL-10 levels were
measured in neonatal and adult mice at various times after infection with Listeria
monocytogenes. Collectively, the data of the study suggested that an overproduction
of IL-10 by macrophages may at least partially explain the increased susceptibility of
neonates to listeriosis (and provide further evidence that cytokine production is
different in adults and neonates). The conclusion of the study was that neonatal
mice produce high IL-10 levels during listeriosis or after the injection of killed
bacteria. Overproduction of the cytokine is apparently detrimental during listeriosis,
but may be beneficial in infections by other pathogens.
4
Francesco Genovese, et. al., Role of IL-10 in a Neonatal Mouse Listeriosis Model, The Journal of Immunology, 1999, 163,
2777-2782.
3

4. Meanwhile, according to another study, high doses of Listeria monocytogenes
overcome the ability of a normal mouse to control the infection, due to massive
bacterial replication. Treatment with an anti-interleukin 10 (IL-10) receptor
monoclonal antibody prevented the fatal course of infection with high doses of
bacteria. This work showed that blocking the receptor for IL-10 may have useful
therapeutic applications.5
In Figure 3 on the next page, it can be seen that an Anti-IL-10 was administered to
the NC/Nga mice to see its effects. In this scenario, an LM of 7.4 x 104 per head was
administered. The result of this figure is not conclusive. It is also inconsistent with
Figure 2. In fact, the decreased serum levels of the IL-10 led to a 0% survival rate by
day 4 post infection (shown by the red line). In the case of the control group (the
blue line), survival of the NC/Nga mice remained steady at 40% from day 6 to day 14
post infection because of the presence of IL-10.
Figure 3. Effects of the Anti-IL-10 Dosage to NC/Nga Mice
In the case of Figure 4 (on the next page), the administration of the IL-10 to the three
types of mice (i.e. NC/Nga, BALB/c, and C57BL/6J) led to their increased survival
rates. In this model, an LM of 4.2 x 105 per head was administered. In the case of
BALB/c and C57BL/6J mice, survival rates increased to 100%. This happened at
day 3 post infection for BALB/c mice while for C57BL/6J, at day 5 post infection. The
result of Figure 4 is also inconsistent with the result of Figure 2.
5
Regina A. Silva and Rui Appelberg, Blocking the Receptor for Interleukin 10 Protects Mice from Lethal Listeriosis, 2001,
American Society for Microbiology
4

5. Figure 4. Effects of IL-10 Dosage to NC/Nga, BALB/c, and C57BL/6J Mice
The role of IL-10 in listeriosis is not entirely clear. Anti-IL-10 treatment resulted in
increased bacterial replication and lethality late in the course of infection, after
producing an early improvement in another study.6 In another report, however, adult
IL-10-deficient mice showed increased resistance to L. monocytogenes,7 while
administration of r IL-10 severely decreased innate defenses against the organism.8
Based on Figure 2 alone, the conclusion would be that the presence of IFN-γ
increased the resistance of the NC/Nga mice against listeriosis. On the other hand,
significantly high levels of IL-10 made the NC/Nga mice highly-susceptible to
Listeriosis. The results of the other figures above (Figures 3-4) did not show
conclusive evidence on the Figure 2 hypothesis. In this regard, additional studies
should be carried out to further understand the real role of IL-10 in listeriosis.
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25. Wagner, R. D., N. M. Maroushek, J. F. Brown, and C. J. Czuprynski, 1994, Treatment with anti-interleukin-10 monoclonal
antibody enhances early resistance to but impairs complete clearance of Listeria monocytogenes infection in mice, Infection
Immunology, 62:2345.
7
26. Day, W., G. Ko¨hler, and F. Brombacher,1997, Both innate and acquired immunity to Listeria monocytogenes infection
are increased in IL-10-deficient mice, Journal of Immunology, 158:2259.
8
27. Kelly, J. P., and G. J. Bancroft, 1996, Administration of interleukin-10 abolishes innate resistance to Listeria
monocytogenes, European Journal of Immunology, 26:356.
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