Both TNF-α receptors are critical for TNF-α–induced leukocyte transmigration. Cumulative effect of TNF-α on leukocyte infiltration to the interstitial space of the cremaster muscle. Following 3 hours of TNF-α treatment, acetone-fixed cremaster specimens were subjected to hematoxylin-and-eosin staining to observe infiltrated leukocytes. Arrows show the infiltrated leukocytes.