  Organ-on-a-chip (OoCs) platforms could revolutionize drug discovery and might
ultimately become essential tools for precision therapy. Although many
single-organ and interconnected systems have been described, the immune system
has been comparatively neglected, despite its pervasive role in the body and
the trend towards newer therapeutic products (i.e., complex biologics,
nanoparticles, immune checkpoint inhibitors, and engineered T cells) that often
cause, or are based on, immune reactions. In this review, we recapitulate some
distinctive features of the immune system before reviewing microfluidic devices
that mimic lymphoid organs or other organs and/or tissues with an integrated
immune system component.
