Thesis (M.A.)--Boston UniversityThe human immune system is capable of detecting and removing foreign invaders such as viruses, microorganisms, and other harmful materials. A key component of this immune response is leukocyte recruitment—a process, in which leukocytes travel from the bloodstream to the site of injury or infection. SIRPα, a protein mainly known to be expressed in myeloid leukocytes, has been shown to contribute to this process by regulating transendothelial migration (TEM)—leukocyte passage through the vascular endothelium. Interestingly, a recent study has detected low levels of SIRPα on surface of cultured endothelial cells. The aim of this study was to confirm endothelial expression of SIRPα and to investigate its role in leukocyte TEM. SIRPα expression on the endothelial cell was confirmed by immunofluorescence microscopy, indirect immunofluorescence and flow cytometry, and by western blot analysis. shRNA silencing and function blocking antibodies were used to block the adhesive function of SIRPα in an in vitro TEM assay under physiological shear flow conditions. The interventions did not alter
leukocyte TEM and we conclude that SIRPα does not play a significant role in leukocyte TEM in vitro
