Correlation Between Elevated Eosinophils and H. pylori Infection
There is evidence of a positive correlation between H. pylori infection and elevated eosinophils in gastric tissue, but an inverse relationship between H. pylori and esophageal eosinophilia.
Gastric Eosinophilia and H. pylori
H. pylori infection appears to stimulate eosinophil activity in gastric mucosa through several mechanisms:
Statistically significant increase of eosinophils has been observed in H. pylori infected gastric mucosa compared to H. pylori negative gastritis with similar activity 1
H. pylori outer membrane vesicles (OMVs) can trigger eosinophil degranulation and release of eosinophil cationic protein (ECP) through specific molecular pathways 2:
- Via direct interaction with eosinophils
- Through upregulation of ICAM-1 on gastric epithelial cells
- By inducing β2 integrin CD11b expression on eosinophils
The H. pylori-derived peptide Hp(2-20) has been shown to:
- Stimulate eosinophil migration through engagement of formyl-peptide receptors (FPR2 and FPR3)
- Induce production of VEGF-A and TGF-beta, key mediators of tissue remodeling
- Cause eosinophil infiltration in rat gastric mucosa after injury 3
Esophageal Eosinophilia and H. pylori
Interestingly, the relationship appears to be inverse when examining esophageal tissue:
A large cross-sectional study of 165,017 patients found that H. pylori infection was inversely associated with esophageal eosinophilia (odds ratio 0.77; 95% CI, 0.69-0.87) 4
A dose-response relationship was observed:
- Higher numbers of esophageal eosinophils were associated with lower prevalence of H. pylori
- Greater severity of histologic effects of H. pylori was inversely associated with esophageal eosinophilia 4
However, a more recent prospective multicenter case-control study of 808 individuals found no significant difference in H. pylori prevalence between eosinophilic esophagitis (EoE) cases and controls (37% vs. 40%, p=0.3) 5
Clinical Implications
When evaluating patients with elevated eosinophils:
Consider the anatomical location - gastric eosinophilia may suggest H. pylori infection, while esophageal eosinophilia is less likely to be associated with H. pylori
Blood eosinophilia alone is not diagnostic for any specific condition, as peripheral eosinophil counts can be elevated in 10-50% of adults and 20-100% of children with various conditions 6
When evaluating peripheral eosinophilia, note that:
- Definitions vary (ranging from >350 to >800 eosinophils/mm³)
- Concurrent allergic conditions may contribute to elevated counts
- Correlation with disease activity is not well established 6
Pitfalls and Caveats
- The relationship between H. pylori and eosinophilia may be confounded by concurrent allergic conditions
- The most recent multicenter case-control study questions the protective role of H. pylori against allergic disorders 5
- Blood eosinophil counts should be interpreted in context of other clinical findings and may require repeated measurements to establish patterns
In summary, while H. pylori appears to stimulate eosinophil activity in gastric tissue, its relationship with systemic eosinophilia and esophageal eosinophilia remains complex and potentially inverse.