Allergen immunotherapy reorients inappropriate immune responses in allergic patients: how SLIT works

Allergen immunotherapy reorients inappropriate immune responses in allergic patients.

Sublingual allergen immunotherapy (SLIT) has been approved in the European Union and Australia as an alternative to subcutaneous allergen immunotherapy (SCIT) for allergic rhinitis patients.

Compared with SCIT, SLIT has a better safety profile (but is it as effective?). Here are some hypotheses that may explained the excellent safety profile of SLIT:

- Oral antigen-presenting cells (Langerhans and myeloid dendritic cells) exhibit a tolerogenic phenotype, despite constant exposure to danger signals from food and microbes that enter the mouth. This reduces the induction of pro-inflammatory immune responses leading to systemic allergic reactions.

- In addition, oral tissues contain few mast cells and eosinophils (located in submucosal areas). In comparison with subcutaneous tissue (in SCIT) these cells are less likely to cause anaphylactic reactions.

SLIT-associated immune responses include the induction of circulating, allergen-specific Th1 and regulatory CD4+ T cells, leading to clinical tolerance (just like SCIT).

40-75% of patients receiving SLIT experience mild, transient local reactions in the oral mucosa. However, these reactions rarely necessitate dose reduction or treatment interruption.

This summary discusses 11 published case reports of anaphylaxis (all nonfatal) diagnosed according to the World Allergy Organization (WHO) criteria. One billion SLIT doses administered worldwide since 2000.

References:

Sublingual allergen immunotherapy: mode of action and its relationship with the safety profile - Calderón - 2011 - Allergy

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