This document summarizes the immunohistochemistry protocol used to analyze ERK1 protein expression in human uterus tissue samples. Key steps included: antigen retrieval using citric acid; blocking of endogenous peroxidase; primary antibody incubation with anti-ERK1 antibody overnight at 4°C; secondary antibody incubation at room temperature for 30 minutes; DAB staining to visualize positive results; hematoxylin counterstaining; dehydration and clearing of slides; and visualization under a microscope. The protocol validated that the anti-ERK1 antibody specifically labeled ERK1 protein in human uterus tissue as expected.