inverted CD4/CD8 T-cell ratio (<1.0) is associated with animmune risk phenotype characterized by increased morbidityand mortality and is correlated with increased levels of T-cellactivation.9-15,31 In asthmatic adults the CD4/CD8 T-cell ratio isinversely correlated with bronchial hyperactivity,27 and a lowerCD4/CD8 ratio has been observed before and during thenatural allergy season in those with atopic allergies.28 Consistentwith these prior findings, we also observed an inversecorrelation between levels of activated CD81 T cells andCD4/CD8 ratios.Nasal cells of participants with M1P1C2 versus M1P1C1sensitization status had different temporal expression patterns ofgenes involved in immune responses. On challenge with HDM inthe ACC, M1P1C1 status was associated with an early robustimmune/inflammatory response followed by a rapid end of thisresponse, despite repeated intervening HDM challenges. Incontrast, M1P1C2 sensitization status was associated with amuted inflammatory response to HDM challenge. Instead of aresolution, as with M1P1C1 status, immune/inflammatoryresponses increased or persisted with continued exposure.Among the pathways tested, the most significant differenceswere in the TH2-, TLR-, and ILC-related genes, which have beenimplicated in cockroach allergy or atopy in general.32-34 In otherinflammatory settings (eg, HIV infection) there is growingevidence that it is not the initial increase in activation thatcontributes to ongoing disease pathogenesis but whether
activation is resolved promptly.35,36 Thus the temporal gene
expression patterns we observed might contribute to the
differences in the symptom severity observed between the study
groups.
The basis for the mitigating effects on AR symptom severity
associated with C1 status is undetermined. Our results might
invoke the hygiene hypothesis of allergy, which asserts that the
cleaner environment related to modernization decreases the
immune system’s exposure to infectious agents, resulting in
increased incidence of allergy.5,16-18,37,38 Thus C1 status might
be a proxy for early-life exposure to not only cockroach but
also possibly microorganisms and other environmental agents.
These exposures might skew the immune response such that
during subsequent exposures to other aeroallergens (eg, pollens),
C1 subjects manifest reduced clinical responsiveness and T-cell
activation. Supporting this contention, exposure to cockroach,
mouse, and cat allergen during an infant’s first year of life had a
strong inverse relationship with recurrent wheezing 2 years
later.16
In summary, our results underscore that the studies conducted
within an ACC have utility for identifying pathogenic
determinants that might underpin high versus low clinical
responses to aeroallergens in a nonconfounded manner.
Cockroach sensitization in polyallergic subjects influences AR
disease severity in an ACC and natural settings. Lower AR
symptom severity associated with cockroach sensitization might
relate to lower T-cell activation in the periphery and a gene
expression pattern that connotes rapid termination of immune/
inflammatory pathways induced by aeroallergen exposure.
These observations have broad implications. Accounting for
the overall aeroallergen sensitization status of participants in
clinical trials might help mitigate confounding. This is because
misallocation of trial participants in the intervention versus
placebo arm with sensitization profiles that associate with
symptom promotion (eg, M1P1C2) versus mitigation (eg,
M1P1C1) might artificially skew statistical analyses. The
same concern applies to investigations of immune correlates
associated with AR severity.
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