Polymorphonuclear neutrophil infiltration intensity as consequence of entamoeba histolytica density in amebic colitis

Background: It has been suggested that the damage observed in invasive amebiasis is related to interactions between polymorphonuclear leukocytes (PMN) and Entamoeba histolytica trophozoites. We analyzed the relation between infiltrating inflammatory cell populations and E. histolytica density in intestinal amebic lesions. Methods: Biopsies obtained endoscopically from patients with amebic colitis were analyzed to describe their morphologic abnormalities. Cellular populations and E. histolytica trophozoites were measured quantitatively in order to assess the correlation between infiltrating inflammatory cell populations and parasite density. Results: Amebic lesions were most often located in the colon (55%). The histopathologic diagnoses were colitis in 31%, erosive colitis in 26%, and ulcerated colitis in 24%. The predominant cellular populations found in the lesions were lymphocytes (59.8%) (3,672 ± 2,413/mm ²) followed by PMN (17%) (1,038 ± 1,171 PMN/mm ²) (p < 0.01). A higher density of PMN infiltration was observed in severe cases. Cellular populations predictive of the presence of E. histolytica trophozoites (p = 0.047) were PMN (p = 0.019) and lymphocytes (p = 0.033). The highest association was found between E. histolytica trophozoites and PMN (p = 0.0221). Conclusions: Neutrophils and lymphocytes, particularly the former, are associated significantly with the density of parasites. Our findings support the theory that PMN interaction with E. histolytica contributes to the pathogenesis of amebic intestinal lesions.