USMLE (United States Medical Licensing Examination) Step 1 Practice Exam

What is the key mechanism of Corticosteroids leading to impaired migration of neutrophils out of the vasculature?

1. Activation of eosinophils

2. Sequestration of lymphocytes

3. Increase in platelet aggregation

4. Activation of neutrophil adhesion molecules

The correct answer is: Activation of neutrophil adhesion molecules

Corticosteroids lead to impaired migration of neutrophils out of the vasculature primarily through their effects on neutrophil adhesion molecules. Corticosteroids promote the upregulation of certain adhesion molecules on endothelial cells, which contributes to the retention of neutrophils within the blood vessels and inhibits their ability to exit into the tissues during an inflammatory response. By affecting the expression of these adhesion molecules, corticosteroids decrease the adhesive interactions that are necessary for neutrophils to adhere to the endothelium and subsequently transmigrate into tissues. This mechanism is crucial for understanding the immunosuppressive actions of corticosteroids and their role in modulating the inflammatory response. The other options presented do not directly explain the role of corticosteroids in impeding neutrophil migration. For instance, while eosinophils and lymphocytes are also affected by corticosteroids, the specific mechanism of impaired neutrophil migration is more closely tied to the alteration of neutrophil adhesion properties rather than the activation or sequestration of other immune cells. Similarly, while increased platelet aggregation can have various effects on hemostasis and inflammation, it is not the primary mechanism through which corticosteroids exert their effects on neutrophil migration.