The molecular mechanisms underlying unexplained recurrent implantation failure (RIF) remain unclear. This study aimed at identifying potential biomarkers, exploring relevant signaling pathways, and analyzing the contribution of immune cell infiltration in RIF. Microarray expression datasets were extracted from the Gene Expression Omnibus database to perform bioinformatic analyses. The results showed that ten hub genes may predict RIF with high specificity and sensitivity (area under the curve = 1.000). Protein–protein interaction analysis revealed close interactions between the hub genes and the endometrial receptivity array. The real-time quantitative polymerase chain reaction further validated three potential biomarkers (RAB32, TRIB2, and FAM155B). Functional enrichment analyses indicated that immune pathways were significantly downregulated and lipid metabolism pathways were significantly upregulated in RIF compared with the controls. Significant negative correlations were observed between fatty acid biosynthesis and the immune pathways. Immune cell infiltration, including those in CD56dim natural killer, dendritic, Th1, Th2, and regulatory T cells, as well as macrophages, was significantly reduced in RIF compared with the controls used herein. This study may provide a novel perspective on the diagnosis and treatment of RIF.

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KEGG P Apelin signaling pathway 5.332880407 4.64643E-06 Calcium signaling pathway 4.517239394 3.03921E-05 cAMP signaling pathway 4.274576486 5.31402E-05 Relaxin signaling pathway 4.265577603 5.42528E-05 cGMP-PKG signaling pathway 3.770418819 0.000169661 Tight junction 3.735498044 0.000183866 Salivary secretion 3.735298811 0.000183951 Alzheimer disease 3.72400395 0.000188797 Pathways in cancer 3.668709189 0.000214433 Focal adhesion 3.428581395 0.