Mechanical force matters in early T cell activation.

Mechanical force has repeatedly been highlighted to be involved in T cell activation. However, the biological significance of mechanical force for T cell receptor signaling remains under active consideration. Here, guided by theoretical analysis, we provide a perspective on how mechanical forces between a T cell and an antigen-presenting cell can influence the bond of a single T cell receptor major histocompatibility complex during early T cell activation. We point out that the lifetime of T cell receptor bonds and thus the degree of their phosphorylation which is essential for T cell activation depends considerably on the T cell receptor rigidity and the average magnitude and frequency of an applied oscillatory force. Such forces could be, for example, produced by protrusions like microvilli during early T cell activation or invadosomes during full T cell activation. These features are suggestive of mechanical force being exploited by T cells to advance self-nonself discrimination in early T cell activation.