Journal Review 1 1.
High-dose exposure to cat is associated with clinical
tolerance - a modified Th2
immune response?
(Clin Exp Allergy 2003;33:1681-5)
2. The relevance of maternal immune reponses to inhalant
allergens maternal
symptoms, passive transfer to
the infant, and development of antibodies in the first
2 years of life (J Allergy Clin
Immunol 2003;111:123-30)
Exposure to allergens plays an important
role in the allergic disease. For dust-mite allergens,
dose-response link between exposure and both sensitization
and asthma. By contrast, recent population-based studies
suggest that having a cat in the house from early childhood
decrease the risk of sensitization and asthma. It is
not exactly known what mechanisms could lie behind this
development of immune tolerance, although Platts-Mills
et al. recently suggested the modification of Th2 immune
response as an possible explanation. They showed that
high-dose exposure to cat allergen can produce IgG and
IgG4 antibody responses with decreased production of
IgE antibodies, and that the response could be regarded
as a modified Th2 response. Recent studies have shown
that expression of the gene for IgG4 can be induced
by the Th2 cytokine, interleukin-4. Hesselmar et al.,
the authors of the former article, intended to test
the hypothesis of modified Th2 response on differing
populations. The investigators also found that significant
portion of children had an immune response with only
IgG4, and no IgE antibodies to cat, and this group of
children had the highest frequency of cat-keeping, but
was not associated with an increased risk of asthma
or allergy. And, as the previous studies shown, there
was a dose-response relationship between low and moderate
exposure to cat and sensitization to cat, whereas a
negative association for high-dose exposure. But the
dose-response relationship for mite exposure and sensitization
was linear. The authors suggest that the modified Th2
response associated with high-dose allergen exposure
is probably due to less IgE production and not due to
any protective effect of IgG4 itself.
The latter article investigated the influence
of maternal immune responses to cat and mite allergens
on the development of immune responses in the infant
and allergic disease during the first 3 years of life.
It showed the same results that were revealed in the
former article, demonstrating the different immune responses
to cat and dust-mite. This article revealed that maternal
IgG antibody was transferred to the infant and might
influence IgG antibody production in the child. The
authors say that these results may indicate the importance
of understanding the mechanisms of tolerance to cats
and raise questions about the independent role of the
mother in the inheritance of allergy. |