Discussion
We showed that solid FPIES reaction on OFC is accompanied by an
elevation of TARC ratio. Our study included eight OFC (six cases) which
pre-OFC TARC levels were over upper limit of age-appropriate value (data
not shown). Two of six cases had eczema, however, the other four cases
lacked eczema. These suggested that TARC ratio could be available
regardless of baseline serum TARC levels.
TARC ratio correlated with post-OFC CRP levels. A recent study
demonstrates that CRP levels increase in positive OFC suggesting
inflammatory mechanisms in FPIES.4 FPIES is thought to
be a T cell-mediated disorder, leading to local T cell infiltration with
exaggerated expression of proinflammatory cytokines such as tumor
necrosis factor-α and suppression of anti-inflammatory cytokine,
transforming growth factor-β.5 An acute FPIES reaction
is also associated with a skewing of the T cells cytokine profiles to
Th2 response.6 On the other hand, regulatory T cells
may play a role in the acquisition of tolerance.7 TARC
promotes intestinal inflammation and counteracts regulatory T
cell-mediated protection from colitis in mice.8Indeed, TARC expression is enhanced in the intestine of experimental
allergic mice with diarrhea,9 although little is known
about the pathological roles of TARC in T cell homing to the intestinal
mucosa. These findings suggest that TARC is involved in the development
of intestinal inflammation of solid FPIES. In contrast to OFC-positive
patients, TARC levels showed no changes in any OFC-negative patients who
finally achieved tolerances of solid FPIES. Thus, TARC ratio might be
used to predict tolerance acquisition.
Our study is limited by retrospective review of small number of patients
from a single institute. Additionally, elicited foods were limited to
EY, wheat, scallop, and soy. Since not all OFC-positive patients showed
elevation of serum TARC levels after OFC, further study is necessary to
investigate correlations between TARC ratio and severity, doses of
challenge, or causative foods.
In conclusion, TARC ratio may be a potentially useful biomarker to
diagnose and manage solid FPIES irrespective of the presence of eczema.
An understanding the pathological roles of TARC may provide new strategy
for the management of solid FPIES.