Manipulation of Costimulatory Molecules by Intracellular Pathogens: Veni, Vidi, Vici!!
Figure 2
Pathogens modulate the expression of costimulatory molecules for their survival.
Sensing of pathogens through PRRs triggers the activation of APCs. (A) Costimulatory molecules, which act as the second signal for T-cell activation, are upregulated on infected cells. Persistence of intracellular pathogens modulates the expression of costimulatory molecules, such as downregulation of CD40/CD80/CD86 and upregulation of PDL-1 on infected APCs. Similarly, retarding the exhibition of CD28/CD40L augments PD-1/CTLA-4 on T cells. (B) Interaction of T cells with the infected APCs impairs the function of T cells by inducing anergy, apoptosis, or exhaustion. (C) Lack of T-cell help impedes the activity of APCs, eventually enhancing the survival of pathogens.