Roles of EC ICAM-2, JAM-A, and PECAM-1 in neutrophil transmigration induced by TNF-α. (A) The role of EC PECAM-1 in neutrophil transmigration as elicited by IL-1β and TNF-α was investigated. Fluorescently labeled WT leukocytes were injected into WT or PECAM^−/− recipient mice treated with intrascrotal IL-1β or TNF-α. Four hours later, adhesion and transmigration of fluorescently labeled cells were quantified. (B) The role of junctional proteins in TNF-α–stimulated migration was investigated. WT or TNFR^−/− fluorescently labeled bone marrow leukocytes were injected into WT, ICAM-2^−/−, JAM-A^−/−, or PECAM-1^−/− recipient mice stimulated with intrascrotal TNF-α. Four hours later, the cremaster was exteriorized and leukocyte responses were quantified. The diagrams on the right illustrate the inflammatory conditions for which the experiments were planned, that is, stimulation of both leukocyte and EC TNFRs (A) or blockade of leukocyte TNFRs (B). Results are mean ± SEM from n = 4 to 14 mice/group. Statistically significant differences are indicated as follows: #P < .05, ##P < .01, +P < .05.