BACKGROUND: Human breast milk (HBM) is an important source of tolerogenic immune mediators that influence the infant immune system. HBM-derived immune components are affected by various factors
however, few studies have examined the relationship between parity and immune cell profiles of HBM. PURPOSE: This study aimed to clarify the effects of parity on HBM immune cell heterogeneity and gene expression by integrating and analyzing publicly available single-cell RNAsequencing (scRNA-seq) datasets. METHODS: We clarified the effects of parity on HBM immune cell heterogeneity and gene expression by integrating and analyzing publicly available scRNA-seq datasets. RESULTS: The proportion of innate immune cells was significantly higher in the primiparous versus multiparous group, whereas the proportion of adaptive immune cells was significantly higher in the multiparous group (P=0.021). The 2 immune clusters were reannotated and classified into monocyte, T/B cell, and CD45¯ groups. The proportions of monocytes and T/B cells were higher in the primiparous and multiparous groups, respectively. In a gene set enrichment analysis of monocytes, genes with a direct role in the infant immune system and immune response-related genes were more highly expressed in the primiparous group. CONCLUSION: Our results support the parity-dependent differences in gene expression between innate and adaptive immune cells.