Neonates,elderly persons,and otherwise immunocompromised patients are particularly susceptible to infections with Listeria monocytogenes.These patients typically have fever and chills,often progressing to hypotension and septic shock.In healthy individuals,however,such intracellular microbes are usually effectively phagocytosed and killed by macrophages,which become activated via:
A)CD40L-CD40 interactions between activated T helper cells and macrophages
B)CD28-B7 interactions between activated T cells and macrophages
C)Fas ligand-Fas interactions between activated cytotoxic T lymphocytes and macrophages
D)TCR-MHC class II interactions between activated T helper cells and macrophages
E)LFA-1-ICAM-1 interactions between activated T cells and macrophages

Question

Quizplus · Accepted Answer

Activated CD4⁺ T cells express CD40 ligand (CD40L),which binds to CD40 on B lymphocytes,macrophages,dendritic cells,and endothelial cells thereby activating these cells.Only activated macrophages can effectively phagocytose and kill intracellular microbes such as Listeria.CD28-B7 and TCR-MHC class II interactions provide signals 2 and 1,respectively,in the activation of T cells by antigen-presenting cells (not the activation of macrophages by T cells).Engagement of Fas by Fas ligand (FasL)on T cells results in apoptosis and provides one of the mechanisms by which CTLs kill their targets.LFA-1-ICAM-1 mediates cell adhesion interactions important in T cell activation and homing.

Neonates,elderly Persons,and Otherwise Immunocompromised Patients Are Particularly Susceptible to Infections