Biology Reference
In-Depth Information
inflammatory markers such as C-reactive protein in peripheral blood
andelevatedIgEtotheAscaris allergen ABA-1 among those with
ABA-1-specific IgG.
52
Single anthelmintic treatments given to infected children appear to
have little effect on the host cytokine response to Ascaris antigens
58
but
giving periodic anthelmintic treatments over time to suppress infections
has been associated with increased Th2 cytokine production to parasite
antigens.
59,60
Thus, although Th2 responses are prominent during active
infections, such responses and perhaps also Th1 responses,
60
are sup-
pressed during chronic infections, an effect that may or may not be
mediated by IL-10.
40,58,60
Neutralization of IL-10 in PBMC cultures had no
effect on frequencies of cells expressing Th1 or Th2 cytokines.
40
Such
modulation of immunity in highly endemic communities may start in
early life: a study of cord blood from newborns of infected and uninfected
mothers showed that the frequencies of antigen-stimulated CD4
cells
expressing IL-4 and IFN-
g
were increased among newborns of infected
compared to uninfected mothers suggesting prenatal immune sensitiza-
tion.
61
There are several birth cohort studies in progress that are
addressing the role of exposure to A. lumbricoides in early life in molding
the immune response to ascariasis.
62,63
รพ
IMMUN
E MODULATION IN ANIMAL M
ODELS
Parasite persistence in the host may require the modulation of the host
immune response through a complex host
parasite interaction.
64
The
effects of such immune modulation may have important non-specific
effects on the regulation of inflammation in the host. Several research
groups have explored the effects of antigen extracts derived from A. suum
parasites on inflammation in murine models of inflammatory disease. The
findings show that different antigen extracts of A. suum have distinct
effects on inflammatory responses with some having strong immuno-
suppressive effects on immune responses and therapeutic effects in
experimental models of asthma
65
and arthritis,
66
while other studies show
that such extracts may also induce inflammation, particularly allergic
inflammation.
67
This latter observation is hardly surprising given that A.
suum infections and/or A. suum antigen preparations are widely used for
the induction of bronchial hyper-reactivity in experimental models of
asthma in primates and other experimental animals.
68,69
Co-immunization of mice with ovalbumin (OVA) and A. suum antigen
fractions have been shown to suppress immune responses to OVA
including the production of specific antibodies of all antibody iso-
types including IgE
70
and anaphylactic IgG1,
71,72
and delayed type
hypersensitivity (DTH) to ovalbumin (OVA).
73
High molecular weight
fractions of A. suum body fluid seemed to account for these effects and
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