Correlation between human neutrophil peptide 1–3 secretion and azurophilic granule (CD63) expression in early childhood caries

Background: In saliva, neutrophil constitutes the most prominent first‑line defense of immune cells against pathogenic microbes. The importance of neutrophils to the host immune systems of neutropenic or patients disabled with regard to their neutrophil function results in a tendency toward serious infections, such as early childhood caries (ECC). The cytoplasmic granules present in neutrophils play a major role in neutrophil‑mediated inflammation. Azurophilic granules contain antimicrobial proteins, such as defensin, a human antimicrobial peptide (HNP 1–3). The aim of this study is to analyze the correlation of HNP 1–3 secretion with CD63 expression on the surface of salivary neutrophils. Materials and Methods: This study constituted a cross‑sectional, analytical observational study. Saliva taken from preschoolchildren between the ages of 4–6 years who had been divided into two groups, i.e., early childhood caries group with decayed, extracted, filled teeth (def‑t) index >6 and caries free with def‑t = 0, was subjected to a HNP 1–3 secretion test using ELISA assay and an expression test for CD63 by means of a flow cytometry test. The results obtained were analyzed using independent t‑test and Pearson correlation (P < 0.05). Results: The secretion of HNP 1–3 in the saliva of ECC was higher (172.6 ± 41.64) compared to that of caries‑free cases (140.39 ± 31.91), whereas the level of CD63 salivary expression in ECC was lower (2.32 ± 0.57) than in the presence of caries (2.67 ± 0.46). Conclusion: In ECC cases, saliva increases HNP 1–3 secretion but decreases CD63 expression on the surface of salivary neutrophils.