Can persistent infection-related antigen exposure maintain immune activation and promote mast-cell activation and type 2 immune skewing?

Persistent exposure to infection-related antigens—such as Borrelia burgdorferi peptidoglycans or viral proteins from SARS-CoV-2 and cytomegalovirus—acts as a continuous trigger that prevents the normal resolution of the immune response, driving chronic inflammation and altered immune phenotypes.

Mechanisms of chronic immune and mast-cell activation

• Receptor engagement: Pathogen-associated molecular patterns (PAMPs) persistently engage host cell-surface and endosomal Toll-like receptors (such as TLR2 and TLR4), sustaining the production of pro-inflammatory cytokines (including TNF-α and IL-6), chemokines, and type I interferons.
• Mast-cell hyperreactivity: Antigens like the SARS-CoV-2 spike protein and B. burgdorferi outer surface protein C (OspC) directly trigger mast-cell degranulation. Chronic TLR signaling primes these cells, significantly amplifying future mediator release.
• IgE-mediated pathways: Persistent antigen exposure drives host class-switching to produce antigen-specific IgE. This IgE binds to high-affinity FcεRI receptors on mast cells, promoting robust degranulation upon subsequent antigen encounter.

Pathways driving type 2 immune skewing

• TCR signaling dynamics: Th2 polarization is highly context-dependent rather than an automatic consequence of chronic exposure. While high antigen doses or strong T-cell receptor (TCR) signaling classically promote Th1 responses, continuous low-dose antigen exposure or weak TCR signaling favors Th2 skewing.
• Molecular reinforcement: This phenotype requires supportive microenvironmental cues, primarily interleukin-4 (IL-4) signaling via STAT6 to upregulate the master transcription factor GATA3. This pathway, often assisted by trained group 2 innate lymphoid cells (ILC2s), establishes a feedback loop that sustains the secretion of IL-4, IL-5, and IL-13.

Bottom line

• Persistent infection-related antigen exposure maintains chronic immune activation and directly drives mast-cell activation and priming, while type 2 immune skewing is a highly plausible but context-dependent outcome optimized by low-dose antigen exposure and supportive IL-4/STAT6/GATA3 signaling.