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The severity of allergic rhinitis in pediatric patients is markedly reduced by administering sublingual immunotherapy by decreasing levels of type 2 innate lymphoid cells (ILC2), ILC2-related cytokines, and their transcription factors in the bloodstream.

Allergic rhinitis (AR) is a widespread immunological disease of the nasal mucosa among children and adults characterized by watery nasal discharge, nasal stuffiness, itching, and sneezing due to exposure to inhaled allergens. A recent study published in BMC Pediatrics aimed to assess the effectiveness of sublingual immunotherapy (SLIT).

The goal of SLIT is to reduce the Th2-biased responses that cause the symptoms of AR. 

For this study, 70 pediatric patients allergic to house dust mice for at least two years were selected as the sample. Forty of the children received SLIT, and 30 received a placebo.

Effects of SLIT on ILC2 Levels

Blood samples were collected from the participants at baseline and after 1 and 2 years of SLIT. There was no significant difference in baseline levels of ILC2 between the SLIT and the control groups. However, after the 1-year interval, the SLIT group showed a remarkable decrease in ILC2, and a similar decrease occurred with 2 years of therapy. In contrast, the control group did not show a significant decline after one and two years.

SLIT Therapy and ILC2-Related Transcription Factors and Cytokines

Compared to initial baseline levels, the mRNA levels of ILC2-related transcription factors, interleukin (IL)-5, IL-13, and nasal eosinophil cationic protein (ECP), showed a marked reduction following therapy with SLIT; nevertheless, the serum ECP levels remained unaffected. Comparatively, levels of transcription factors and cytokines remained constant in the control group.

Dermatophagoidesfarinae Drops in SLIT Therapy and ILC2 Frequency

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Dermatophagoides farinae drops used in SLIT therapy are recommended by several guidelines as the treatment of choice in AR. Its effectiveness is attributed to its ability to inhibit the Th2 response, which has a similar mechanism of action as ILC2. As disease severity in AR is determined by the level of ILC2 and related cytokines, it is postulated that SLIT also decreases ILC2 frequency.

Immunomodulatory Effect of SLIT on ILC2 Levels

The control group with AR involved in the study showed an opposite, positive correlation to the intervention, resulting in elevated ILC2 levels following exposure to the house dust mites allergen extract, suggesting that the immunomodulatory effect of SLIT on ILC2 in one of the pathways by which it improves symptoms of AR.

Source:

Wang, X., Shen, Y., Hong, S., Kang, H., & Ke, X. (2023). Changes in type 2 innate lymphoid cells and serum cytokines in sublingual immunotherapy in pediatric patients with allergic rhinitis. BMC Pediatrics, 23(1). https://doi.org/10.1186/s12887-022-03788-z