The study looked at how the antimicrobial peptide LL‑37 and other immune proteins are present in human placenta at different stages of pregnancy. LL‑37 was only found in a type of placental macrophage (Hofbauer cells) and its amount increased as the pregnancy progressed. Other defence proteins also rose with gestational age, showing a coordinated immune network in the placenta.

Numerous studies have shown the presence of multiple defence factors in placental tissue, although their role is partially understood; therefore, the aim of this study was to evaluate the expression of nuclear factor-kappa B (NF-&#x3ba;B); human beta-defensin 2, 3, and 4 (HBD-2,3,4); cathelicidine (LL-37); heat shock protein 60 (HSP60); and interleukin 10 (IL-10) in dissimilar gestational week placental tissue and display correlations between immunoreactive cells. A total of 15 human placental tissue samples were acquired from mothers with different gestational weeks: 28, 31, and 40. Routine staining and immunohistochemistry for the samples were executed. The evaluation of data was performed with semi-quantitative methods, and, for statistical analysis, the Kruskal-Wallis test was used. Spearman's rank correlation was used for calculating correlations. NF-&#x3ba;B, HBD- 2,3,4, HSP60, and IL-10 expression were discovered in every examined placental tissue cell type. LL-37 expression was found only in Hofbauer cells. A rise in expression with higher gestational weeks was noted in LL-37-positive Hofbauer cells (<i>p</i> = 0.03), HBD-3-positive cytotrophoblasts (<i>p</i> = 0.007), endothelial cells (<i>p</i> = 0.024), extraembryonic mesodermal cells (<i>p</i> = 0.004), and HBD-4-positive endothelial cells (<i>p</i> = 0.001). Numerous statistically significant moderate and strong positive correlations between defence factors were discovered. The persistence of Hofbauer cell accumulations underlines the growing significance of placental macrophages in placental protection. The expression of positive defence factors and a rise in expression in tissue protection factors (HBD-3, LL-37, HBD-4) in higher gestational weeks may indicate these factors as the most significant protectors of the placenta in ontogenetic aspects. The high number of statistically significant positive and negative correlations between positive cells show a strong network to sustain distressed placental growth and therefore pregnancy.