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Departments of
*
Neurology and
Pathology, University of Southern California School of Medicine, Los Angeles, CA 90033; and
Laboratory of Host Defenses, National Institute of Allergy and Infectious Diseases, Bethesda, MD 20892
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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, IFN-
(1), cAMP
(2), IL-1, and PGE2
(3). Despite extensive knowledge about NO regulation, the
role of NO in tissue inflammation is controversial, as illustrated by
studies involving the animal model for multiple sclerosis, experimental
allergic encephalomyelitis (EAE). Some investigators concluded that NO
is involved in the pathogenesis of EAE (4, 5, 6, 7, 8, 9, 10, 11, 12), while
others reported protective effects of NO (13, 14, 15, 16).
It is improbable that NO forms a major effector molecule during CNS
inflammation and tissue damage, because NO is only a weak oxidant and
reacts more rapidly as an antioxidant (17). NO may be
involved in protection against cytokine-induced systemic damage
(18), as well as inhibition of leukocyte adhesion and
migration through the endothelial cell layer (19). In
addition, NO has been implicated as a major macrophage-derived
immunosuppressive factor for T cell immunity (20, 21). NO
functions as a powerful inhibitor of T cell proliferation (22, 23) and also inhibits NF-
B activation (24).
Surprisingly, iNOS-deficient mice express increased EAE severity
compared with wild-type mice (25, 26), supporting a
protective role for NO.
NO can be transformed by reacting with another enzymatically produced free radical, superoxide (O2-) to form the pro-oxidant peroxynitrite (ONOO-) (27, 28, 29, 30), which has been implicated in EAE (31, 32, 33). The extremely strong reaction between the free radicals NO and O2-, which occurs three times faster than the rate at which superoxide dismutase (SOD) scavenges O2- (27), could regulate NO’s activity and at the same time be responsible for the widely studied cytotoxic effects of NO. The studies described here focus on the regulation of NO’s activity by O2-, but not on the role of ONOO-. Thus, the fate of NO may determine whether or not it provides immunoregulatory protection. This concept was tested by studying the regulation of NO activity by simultaneous O2- production by macrophages. As demonstrated earlier with chemical NO donors in the absence of macrophages, NO strongly inhibits the proliferation of activated Th cell clones directly, without reducing their cytokine production (34). This characteristic was used in the current studies for the quantification of the functional activity of macrophage-derived NO.
In humans, mutations in any of the four structural proteins of the NADPH oxidase lead to chronic granulomatous disease, an inherited immunodeficiency in which children develop recurrent, severe, life-threatening bacterial and fungal infections and tissue granuloma formation. NADPH oxidase produces O2- and forms an essential factor in the protection against infections (35), but its role in immune regulation or in EAE has not been studied. Besides a potential cytotoxic role for O2- or its derivatives during inflammation, NADPH oxidase may regulate the activity of macrophage-derived NO and could be important in EAE. To study this, we used mice with a targeted deletion in p47phox, an essential component of the NADPH oxidase enzyme complex. The results indicate that the NO-dependent inhibitory activity of macrophages is reversed by NADPH oxidase, which could be involved in the resistance of p47phox knockout (pKO) mice to active EAE induction.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The NOS inhibitor L-NMA and its inactive isomer
D-NMA, as well as the NO donor
S-nitroso-N-acetyl-D,L-penicillamine
(SNAP) were purchased from Alexis (San Diego, CA). Recombinant mouse
IFN- was obtained from PharMingen (San Diego, CA). All other
reagents were obtained from Sigma (St. Louis, MO). The synthetic
peptide derived from myelin-oligodendrocyte glycoprotein (MOG) sequence
35–55 was produced by the Microchemical Core Facility at the
University of Southern California Comprehensive Cancer Center.
Mice
Gene deletants were created in the 129 background strain and bred on C57BL/6 as described (35). Heterozygous deletants were crossed back onto the C57BL/6 background and then intercrossed. Homozygous p47phox deletants and wild-type (WT) littermates were used for the described experiments. SJL mice were obtained from The Jackson Laboratory (Bar Harbor, ME).
T cells
SJL-derived T cell clones 39A1 and 41D5 are specific for the myelin proteolipid protein peptide 139–151, with identical fine-specificity for individual amino acids within this sequence (36). Clone 39A1 belongs to the Th1 subset, while 41D5 represents the Th2 subset. The T cell clones are maintained by the periodical stimulation with irradiated spleen cells and Ag as described (37). For the experiments described here, resting T cells were stimulated with immobilized anti-CD3 mAb (PharMingen) for 20 h as described previously (37).
Macrophage-T cell cocultures
Peritoneal macrophages (PEC) were harvested 3 days following the
injection of 2.5 ml thioglycollate medium (4%) and cultured for 2
h in microtiter plates at 0.8 x 105 large,
granulated mononuclear cells per well, followed by removal of the
nonadherent cells. Culture medium for macrophages consisted of
high-glucose DMEM (Life Technologies, Gaithersburg, MD) supplemented
with 10% FCS, 15 mM HEPES, 2.5 mM L-glutamine, penicillin
(100 U/ml), and streptomycin (100 µg/ml). To induce NO production in
macrophages, the cells were stimulated with LPS (0.1 µg/ml) and
recombinant mouse IFN- (10 U/ml) for 20 h. After washing the
adherent PEC cultures, anti-CD3-stimulated T cells were washed and
transferred to the PEC cultures at 105 T cells
per well. To study the effect of
O2- on NO activity, some
cultures received PMA (0.2 µg/ml) at the onset of the coculture,
which induces immediate O2-
production by the NO-producing PEC. Because the activated T cells were
added at the same time, the effect of NO on the T cells can be examined
in the presence or absence of
O2-. The cocultures were
simultaneously pulsed with [3H]TdR (0.5
µCi/well) and incubated for 16 h before harvesting the cells
onto fiberglass filters and counting in a scintillation counter.
Results are presented as the total [3H]TdR
incorporation in cpm x 10-3.
O2- production
PEC, cultured for 24 h at 106 cells per well, were washed and stimulated with PMA (0.2 µg/ml) in DMEM in the presence of cytochrome c (200 µg/ml). After 1 h, the supernatants were centrifuged at 15,000 rpm and the absorbence at 550 nm was measured.
Immunization of mice
pKO and WT mice were immunized s.c. with 300 µg MOG35–55 in CFA containing 500 µg Mycobacterium tuberculosis HR37A, in a volume of 200 µl, divided over two or three dorsal sites. In addition, pertussis toxin (200 ng) was injected i.p. The immunization was repeated after 7 days. A total of 11 mice from each strain was immunized, divided over two separate experiments with five or six mice from each strain. The mice were scored daily as follows: 0, no symptoms; 1, weak tail; 2, paraparesis; 3, severe paraparesis including occasional leg dragging; 4, paralysis; 5, moribund.
Histology
Brain and spinal cord were embedded and frozen in liquid nitrogen. Cryostat sections (6–8 µm) were prepared and fixed in acetone and subsequently stained in hematoxylin for 1 min.
Lymphoid cell proliferation
Dissociated lymph node cells (LNC) or spleen cells were cultured at 4 x 105 mononuclear cells per well with MOG35–55 (20 µg/ml) for 64 h, with the last 16 h in the presence of [3H]TdR (0.5 µCi). The cells were harvested to measure the incorporated [3H]TdR. Either the total incorporation or the stimulation index (total over background incorporation) is shown, as indicated.
Cytokine production
Supernatants from cultures described above were harvested after 48 h and assayed for cytokines by ELISA using Ab pairs and standards from PharMingen, according to the manufacturer’s procedure. Net cytokine production was expressed as the difference between Ag-stimulated and background levels.
Nitrite/nitrate production
Combined nitrite and nitrate levels were measured in culture supernatants using a Cayman’s kit (Alexis), according to the manufacturer’s instructions. The culture medium itself contained low nitrate levels.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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To evaluate the efficiency at which macrophage-derived NO inhibits
Th cell proliferation, Th1 cells were activated with immobilized
anti-CD3 mAb and subsequently transferred to cultures of adherent
PEC, which had previously been stimulated with LPS and IFN-, as
described in Materials and Methods. To determine the
contribution of NO toward the inhibition of T cells by macrophages, the
NOS inhibitor L-NMA was added to some cultures.
Fig. 1
A shows the
effectiveness of L-NMA in inhibiting NO
production by stimulated macrophages. The concentrations of
L-NMA that completely inhibited NO production
(
0.5 mM) also induced optimal T cell proliferation, whereas the
inactive isomer D-NMA was without effect (Fig. 1B). Similar data were obtained with Th2 cells, while the
contribution of the macrophages in the total cell proliferation was
minimal (results not shown). The procedure described here was used in
the following experiments to examine the regulation of NO’s functional
activity by O2-.
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Because O2- has a strong
affinity for NO, we hypothesized that simultaneous
O2- production may prevent the
inhibitory effect of NO on T cell proliferation. Adherent PEC,
previously stimulated to induce NO production, were treated with PMA,
which induces O2- production in
the PEC (see insert in Fig. 1
C) immediately following the
addition of the activated T cells to the PEC. In the absence of PMA,
the PEC again completely inhibited the proliferation of the T cells,
which was reversed by the addition of high levels of
L-NMA, as expected (see Fig. 1C). The
[3H]TdR incorporation of the PEC alone was
negligible (<1 x 103 cpm), also in the
presence of L-NMA or PMA. In the presence of
maximal NO production by the macrophages, i.e., in the absence of
L-NMA, PMA had no significant effect on T cell
proliferation. However, in the presence of a low level of
L-NMA, which by itself induced only a slight
increase in T cell proliferation, a substantial increase was induced
when PMA was added simultaneously (see Fig. 1D). Apparently,
a submaximal NO concentration was required to observe PMA’s effect.
The addition of an NOS inhibitor forms a more sensitive tool in the
regulation of NO production than variations in the concentration of the
stimulants LPS and IFN-; thus, the optimal concentration of
L-NMA to help uncover T cell proliferation by PMA
varied between experiments from 0.025 to 0.05 mM (results not
shown).
These results indicate that PMA induced a process that neutralized
NO’s inhibitory activity. Notably, the addition of SOD reversed PMA’s
effect (see Fig. 1C), suggesting that
O2- production was responsible
for the inactivation of NO by PMA. To control for the effect of SOD,
heat-inactivation of SOD neutralized its effect on T cell
proliferation; furthermore, production of hydrogen peroxide by SOD was
not responsible for its function, because catalase (60 U/ml) did not
reverse the effect of SOD (results not shown).
A probable explanation for the inactivation of NO by
O2- is the transformation of NO
to ONOO-. So far, we and others have been unable
to convincingly confirm the extracellular formation of
ONOO- by macrophages in vitro. Therefore, an
alternative explanation for the above described results was examined,
i.e., whether macrophage-derived
O2- could enhance T cell
proliferation directly, thus overriding the effect of NO without
reacting with it. To address this question, the production of NO and
O2- were separated over time to
prevent their interaction. This was approached by performing the
initial anti-CD3 mAb-induced T cell stimulation in the presence of
the NO donor SNAP, which inhibits T cell proliferation for at least
40 h (34). The NO-treated T cells were subsequently
transferred to adherent PEC cultures in the presence of
L-NMA to prevent the production of NO by the macrophages.
In the absence of NO production, a direct effect of
O2- from PMA-activated PEC on T
cell proliferation was not detected, neither with NO-pretreated nor
with uninhibited T cells (Fig. 1D). Therefore, these
experiments demonstrate that macrophage-derived
O2- did not directly stimulate
the proliferation of the T cells. Instead, it can be concluded from the
results in Fig. 1C that
O2- prevents the profound
inhibition of T cell proliferation by macrophage-derived NO, probably
by reacting with NO. The studies described here raise the possibility
that T cell proliferation can be regulated by the balance between
O2- and NO.
Role of NADPH oxidase in the regulation of NO activity
Because extracellular SOD reversed the effect of PMA on NO activity, and because O2- cannot readily penetrate the cell membrane, O2- appears to be produced extracellularly, where it is thought to inactivate NO. Because a major source for extracellular O2- production is NADPH oxidase, the regulation of NO’s activity toward T cell proliferation by macrophages from NADPH oxidase-deficient (p47phox -/- or pKO) mice was examined.
Cocultures of prestimulated PEC and preactivated T cells were incubated
as described above. Despite MHC incompatibility, stimulated PEC from
both WT and pKO mice inhibited T cell proliferation equally well, which
was reversed by high levels of L-NMA, as expected (Fig. 2). In the presence of low levels of
L-NMA, stimulation with PMA reversed the inhibitory effect
of NO in PEC from WT mice, similar to results shown in Fig. 1. However,
the addition of PMA to PEC derived from pKO mice had no stimulatory
effect on T cell proliferation. This indicates that the lack of
functional NADPH oxidase results in the preservation of NO activity and
confirms that O2- inactivates
NO in normal PEC. In addition, these results confirm that in the
presence of activated macrophages, PMA does not directly stimulate the
T cells. Therefore, the results described here indicate that
O2- production by NADPH oxidase
regulates the activity of NO and thus T cell proliferation.
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To study the role of NADPH oxidase in active EAE induction, 11
mice from pKO and WT strains were immunized with
MOG35–55. The WT mice developed modest (three
mice with clinical score 
3) or severe (seven mice with clinical score
4) EAE, with only one WT mouse showing no obvious signs of EAE. In
contrast, none of the 11 pKO mice showed any clear signs of EAE (see
Fig. 3). Some pKO mice received a
clinical score of 1 on a few occasions, only to indicate that they did
not lift their tail during the observation, although tail weakness was
not obvious otherwise. Histological examination of the CNS of the
immunized pKO mice revealed normal tissue with no apparent inflammatory
cells. In contrast, WT mice exhibited extensive perivascular
infiltration of mainly mononuclear leukocytes typical of EAE, which
generally correlated with clinical disease activity (results not
shown).
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To compare the intensity of the immune response to the
encephalitogen, which is essential for the development of EAE, the
response of lymphoid cells from both mouse strains to MOG in vitro was
examined. As shown in Fig. 4A,
similar proliferative responses were observed in LNC from pKO and WT
mice. In addition, the cytokine production by spleen cells in response
to MOG was comparable as well. A strong IFN- production was observed
in both pKO and WT mice (see Fig. 4B). In both strains,
IL-10 production was weak, while IL-4 or IL-5 production in response to
MOG was undetectable (results not shown). These results indicate that
the immune response generated in the lymph nodes of pKO and WT mice was
both quantitatively and qualitatively similar. Therefore, neither the
intensity nor the type of immune response could explain the absence of
EAE in the pKO mice.
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The resistance of pKO mice to EAE indicates that NADPH oxidase is
essential for disease development. This may reflect the deleterious
effects of reactive oxygen intermediates, or it may indicate a central
role for ONOO-. In contrast,
O2- may also function to
prevent the NO-dependent inhibition of T cell proliferation, as
observed with pKO macrophages in vitro. This possibility was supported
by results obtained with the in vitro activation of spleen cells from
immunized pKO mice, which in contrast to their LNC, generally
proliferated poorly in response to MOG, whereas WT spleen cells in
general responded well (Fig. 5A). In contrast, the cytokine
production by MOG-stimulated spleen cells from pKO mice was similar to
that of WT mice, as shown above in Fig. 4. This pattern of T cell
responses (no proliferation, but normal cytokine production) is
reminiscent of the effect of NO on T cell activity (34).
Indeed, the addition of a NOS inhibitor uncovered a good proliferative
response to MOG35–55 in spleen cell cultures
derived from the pKO mice, raising it to a similar level as in WT
spleen cells (Fig. 5, B and C). The lower degree
of Ag-specific proliferation in pKO spleens could not be explained by
increased NO production, because the total nitrite plus nitrate levels
generated by pKO or WT spleen cultures in response to Ag were similar
(Fig. 5D). This may indicate a higher degree of interaction
between NO and O2-, resulting
in a lower level of functional NO in WT compared with KO mice, which is
consistent with the proliferation data. Comparison of nitrite vs
nitrate levels was inconclusive and requires more study. In addition,
these results imply that immune spleen cell cultures increased their NO
production upon the addition of Ag, resulting in poor T cell
proliferation in pKO splenic cultures.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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In the current studies, PMA was used to induce immediate O2- production in stimulated, NO producing macrophages, which resulted in the prevention of NO’s inhibitory activity. As a control, it was shown that in the presence of NO, PMA did not enhance T cell proliferation directly, as demonstrated convincingly with cultures containing NADPH oxidase-deficient macrophages, nor could PMA overcome high levels of NO from normal macrophages. This is confirmed by earlier studies examining the inhibition of T cell proliferation by a chemical NO donor (34). Apparently, NO inhibits T cell proliferation downstream of protein kinase C activation by PMA and leaves cytokine production by the T cells virtually intact.
The presence of low levels of L-NMA was important to observe PMA’s effect on T cell proliferation, because in the absence of L-NMA, PMA only slightly inactivated NO. Maximal NO production may overwhelm or simply inhibit O2- production (40). The optimal concentration of L-NMA varied slightly between experiments. Therefore, parallel experiments were routinely performed with different concentrations of L-NMA, of which usually one concentration was optimal. Apparently, the balance between O2- and NO is delicate in this simplified system, comprised of purified macrophages and T cells. However, the results with ex vivo-stimulated spleen cells from immunized mice indicate that this balance can be reached in a more physiological system, suggesting that NADPH oxidase may inhibit NO’s activity and thus may uncover T cell proliferation in vivo as well.
The demonstration of extracellular ONOO- formation by cells in vitro as a consequence of the extremely high affinity between NO and O2- (27, 28), although likely to occur, has so far been inconclusive. Therefore, an alternative explanation of the results was examined, i.e., that O2- may directly stimulate T cell proliferation, even in the presence of inhibitory NO levels without actually interacting with NO. However, O2- from PMA-treated PEC caused only a marginal increase in NO-pretreated Th cell proliferation, which was not significantly reversed by SOD. These studies indicated that O2- produced by PEC was not directly involved in the stimulation of the T cells. Instead, O2- appears to inactivate NO, a strong inhibitor of T cell proliferation. As a consequence of the transformation of NO by O2-, other regulatory functions of NO may be impaired as well. These include inactivation of macrophages (20, 21) and the inhibition of lipid peroxidation (41, 42), which was demonstrated using purified myelin as well (29). These features render the preservation of NO activity potentially important during CNS inflammation.
In this report, the major source of NO-inactivating
O2- was identified as NADPH
oxidase. Therefore, other oxidases appear not to contribute
substantially to the NO-neutralizing
O2- production. Possibly, the
localization, timing, and amount of
O2- production are crucial.
Because neither O2- nor
exogenous SOD are membrane permeable, it can be concluded that the
SOD-inhibited O2- was produced
extracellularly. This suggests that ONOO-
formation also occurs extracellularly. A schematic representation of
the possible sequence of events involved in either the preservation of
functional NO or its transformation to ONOO- is
shown in Fig. 6. Intracellularly produced
NO diffuses freely through the cell membrane, and, if unaffected by
O2- (due to the presence of SOD
or to a mutation or inactivity in NADPH oxidase), NO inhibits T cell
proliferation. However, when NADPH oxidase is activated simultaneously,
O2- is formed close to the
extracellular face of the cell membrane. Here, it presumably interacts
with NO molecules that have just passed through the cell membrane on
their way out of the cell. Besides the presumed formation of
ONOO- extracellulary, this results in the
prevention of NO-dependent inhibition of T cell proliferation.
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Notably, results in this report further indicate that the interaction between NO and O2- may be important during immune responses in vivo, because spleen cells from immune mice demonstrated reduced Ag-specific T cell proliferation ex vivo when NADPH oxidase was disrupted and unable to regulate NO activity. LNC from immunized pKO mice responded to Ag in a similar fashion as those from WT mice as early as 12 days p.i., indicating the general absence of regulation by NO in lymph nodes, also at early time points after immunization. Thus, it can be concluded that the absence of Ag-specific immune responses in pKO spleens is a local, not a systemic, phenomenon, possibly reflecting a higher concentration of macrophages in the spleen. A strong indication of the significance of immune regulation by NO and O2- could be found in the virtually complete resistance of pKO mice to actively induced EAE. In light of their inhibited spleen cell responses, this may indicate a form of immunodeficiency as a consequence of excessive NO activity in the pKO mice. Inhibition of NO production in pKO mice may be a way to approach this issue. However, the contradictory results in the literature concerning the effect of NO inhibition on EAE development indicate that this approach has dualistic effects, possibly related to the fact that NO has a role in ONOO- formation at inflammatory sites as well. Because a good proliferative response could be demonstrated in lymphoid tissue from EAE-resistant pKO mice, it appears that their genetic defect does not affect the induction, but rather the execution of the immune response that normally leads to EAE development. This is currently under investigation using cell transfers between pKO and WT mice.
The results described here indicate that in the absence of NADPH oxidase, a spleen cell subpopulation produces enough functional NO during an immune response to inhibit the proliferation of T cells. These NO-producing cells may be the same as the recently described splenic ScaI/Mac1+ macrophages, which suppress T cell responses through NO activity (45). During tissue inflammation, similar cells may accumulate, as exemplified by the effect of elicited PEC on T cell proliferation in vitro.
An implication of the results described here is that a T cell regulatory role for NO is less prevalent in draining lymph nodes, where immune responses are initiated. However, although the T cells in the lymph nodes of immunized pKO mice are stimulated, they appear unable to induce EAE in these mice. If NO is involved in the resistance to EAE in the pKO mice, the site of this activity is unclear, but does not seem to include the draining lymph nodes. Furthermore, if, as suggested here, the inhibition of EAE in the pKO mice is regulated peripherally, it may be concluded that activated T cells do not directly migrate from the draining lymph nodes to the CNS, but instead may first be checked elsewhere, possibly in the spleen.
Another implication is that during an immune response in normal spleen cells, both O2- and NO are produced as a consequence of Ag recognition by T cells. Macrophages produce high levels of NO following their Ag-specific stimulation of Th1, but not Th2, cells, resulting in the inhibition of T cell proliferation.4 Furthermore, the balance between O2- and NO may dictate the extent of an immune response in vivo, either at the site of inflammation, e.g., in the CNS, or peripherally, e.g., in the spleen. It is suggested here that this balance regulates the extent of an immune response, with T cell suppression resulting from excess NO, but T cell proliferation following increased O2- production by NADPH oxidase, even during NO production. Besides preventing NO’s T cell regulatory activity, O2- transforms NO from an immunoregulatory factor into the oxidative compound ONOO-, which could be involved locally in tissue damage during inflammation. However, the data reported here suggest that NO may perform an important immunoregulatory role peripherally as well, during the generation of an immune response. On the same note, it can be hypothesized that excessive functional NO activity without simultaneous O2- production could inhibit protective T cell responses, e.g., during immunocompromised conditions. In this case, O2- production and thus NO inactivation would be beneficial, allowing T cell proliferation to occur. In conclusion, the interaction between NO and O2- may play a central role in the control over the execution of immune responses in general (possibly in the spleen), without affecting the induction of immune responses in the lymph nodes. Although an essential role for NADPH oxidase in tissue damage during CNS inflammation has not been ruled out, these studies indicate that NADPH oxidase may be essential to allow the development of a strong immune response, such as occurs during EAE.
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Acknowledgments |
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Footnotes |
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2 Address correspondence and reprint requests to Dr. Roel C. van der Veen, University of Southern California School of Medicine, Department of Neurology, 1333 San Pablo Street, MCH 142, Los Angeles, CA 90033.
3 Abbreviations used in this paper: NOS, NO synthase; iNOS, inducible NOS; L(D)-NMA, N-monomethyl-L(D)-arginine; EAE, experimental autoimmune encephalomyelitis; O2-, superoxide, SOD, superoxide dismutase; SNAP, S-nitroso-N-acetyl-D,L-penicillamine; pKO, p47phox-/-; PEC, peritoneal macrophage; WT, wild type; LNC, lymph node cell; MOG, myelin-oligodendrocyte glycoprotein; ONOO-, peroxynitrite.
4 R. C. van der Veen, T. A. Dietlin, L. Pen, J. Dixon Gray, and F. M. Hofman. Induction of nitric oxide during antigenic stimulation of T helper 1 cells by macrophages regulates T cell proliferation. Submitted for publication.
Received for publication October 14, 1999. Accepted for publication March 6, 2000.
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C.-L. Chen, C.-T. Lee, Y.-C. Liu, J.-Y. Wang, H.-Y. Lei, and C.-K. Yu House Dust Mite Dermatophagoides farinae Augments Proinflammatory Mediator Productions and Accessory Function of Alveolar Macrophages: Implications for Allergic Sensitization and Inflammation J. Immunol., January 1, 2003; 170(1): 528 - 536. [Abstract] [Full Text] [PDF]
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S. Yang, A. Panoskaltsis-Mortari, M. Shukla, B. R. Blazar, and I. Y. Haddad Exuberant Inflammation in Nicotinamide Adenine Dinucleotide Phosphate-Oxidase-Deficient Mice After Allogeneic Marrow Transplantation J. Immunol., June 1, 2002; 168(11): 5840 - 5847. [Abstract] [Full Text] [PDF]
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E. A. Patton, A. C. La Flamme, J. A. Pedras-Vasoncelos, and E. J. Pearce Central Role for Interleukin-4 in Regulating Nitric Oxide-Mediated Inhibition of T-Cell Proliferation and Gamma Interferon Production in Schistosomiasis Infect. Immun., January 1, 2002; 70(1): 177 - 184. [Abstract] [Full Text] [PDF]
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K. H. Ramsey, I. M. Sigar, S. V. Rana, J. Gupta, S. M. Holland, and G. I. Byrne Role for Inducible Nitric Oxide Synthase in Protection from Chronic Chlamydia trachomatis Urogenital Disease in Mice and Its Regulation by Oxygen Free Radicals Infect. Immun., December 1, 2001; 69(12): 7374 - 7379. [Abstract] [Full Text] [PDF]
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L.-Y. Xu, J.-S. Yang, H. Link, and B.-G. Xiao SIN-1, a Nitric Oxide Donor, Ameliorates Experimental Allergic Encephalomyelitis in Lewis Rats in the Incipient Phase: The Importance of the Time Window J. Immunol., May 1, 2001; 166(9): 5810 - 5816. [Abstract] [Full Text] [PDF]
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A. E. Juedes and N. H. Ruddle Resident and Infiltrating Central Nervous System APCs Regulate the Emergence and Resolution of Experimental Autoimmune Encephalomyelitis J. Immunol., April 15, 2001; 166(8): 5168 - 5175. [Abstract] [Full Text] [PDF]
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) by O2- from NADPH oxidase.
See Discussion for explanation. A compound with a dot
indicates a free radical. Arrows with filled head indicate pathways;
arrows with open head indicate an increase (up) or a decrease (down) in
the process aligned by an arrow.