Functional Recognition Theory and Type 2 Immunity: Insights and Uncertainties

Abstract

Type 2 immunity plays an important role in host defense against helminths and toxins while driving allergic diseases. Despite progress in understanding the biology of type 2 immunity, the fundamental mechanisms regulating the type 2 immune module remain unclear. In contrast with structural recognition used by pattern recognition receptors, type 2 immunogens are sensed through their functional properties. Functional recognition theory has arisen as the paradigm for the initiation of type 2 immunity. However, the vast array of structurally unrelated type 2 immunogens makes it challenging to advance our understanding of type 2 immunity. In this article, we review functional recognition theory and organize type 2 immunogens into distinct classes based on how they fit into the concept of functional recognition. Lastly, we discuss areas of uncertainty in functional recognition theory with the goal of providing a framework to further define the logic of type 2 immunity in host protection and immunopathology. ImmunoHorizons, 2022, 6: 569-580.

Spatial microniches of IL-2 synergize with IL-10 to drive lung migratory Th2 cells in response to inhaled allergen

“…Many critical pathways are well known to support Th2 differentiation, including IL-4 and STAT6 signaling to GATA3, the master regulator of Th2 cells, yet the precise pathways that initiate Th2 cells in response to inhaled allergens remain unclear 3,4 . Given the diversity of antigens that can drive Th2 responses, both tissue-specific and antigenspecific pathways to Th2 cells have been postulated 1,5 .…”

Lactobacillus plantarum isolated from kimchi regulates inflammation by increasing interleukin‐10 secretion by antigen‐presenting cells, leading to diminishing of STAT5 phosphorylation in Th2 cells

“…Type II immunity is induced by infections with extracellular parasites and allergens, which cause allergic inflammatory disease. Th2 cells and type 2 innate lymphoid cells (ILC2s) are representative cell subtypes that are involved in these immune processes, in which they secrete various cytokines, such as IL-4, IL-5, IL-9, and IL-13 (Rahimi & Sokol, 2022). The effects of LAB in aspects of immune response have been investigated along with its immunomodulatory influence (Abd Rahim et al, 2023;Alameri et al, 2022).…”