Do basophils participate in IgE-mediated allergic responses?

Basophils serve as critical cellular coordinators of allergic inflammation, linking immediate hypersensitivity with sustained, chronic tissue responses.

Mechanistic activation and recruitment

• Receptor signaling: Human basophils constitutively express the high-affinity IgE receptor ($Fc\epsilon RI$). The cross-linking of receptor-bound IgE by multivalent antigens triggers intracellular signaling cascades, initiating rapid degranulation and de novo cytokine synthesis.
• Recruitment loops: Tissue-resident mast cells also rapidly release histamine upon $Fc\epsilon RI$-mediated cross-linking. This histamine acts through the H4 receptor to actively recruit circulating basophils to allergy sites, amplifying the late-phase response.

Immediate and sustained inflammatory pathways

• Acute symptomatology: Activated basophils undergo rapid degranulation to release histamine, a vasoactive mediator that directly drives immediate hypersensitivity symptoms such as bronchoconstriction, itching, swelling, vasodilation, rhinorrhea, and urticaria.
• Chronic inflammation: Basophils act as the primary early source of type 2 cytokines (IL-4 and IL-13) in human peripheral blood. These mediators propagate allergic inflammation by promoting Th2 cell differentiation, stimulating IgE class switching in B cells, and recruiting tissue-damaging eosinophils to sustain inflammation.

Bottom line

• Basophils play a central, dual-phase role in allergic biology by rapidly releasing histamine to drive immediate symptoms, while simultaneously secreting IL-4 and IL-13 to orchestrate and maintain chronic type 2 allergic inflammation.