Background: Poly(amidoamine) (PAMAM) dendrimers are widely used biomedical polymers, which are extensively applied in drug delivery, gene delivery, contrast agent, etc. In these biomedical applications, the bio-safety of the PAMAM dendrimers is a critical issue, which affects not only their toxicity to the host but also the expected in vivo biofunctions of the materials. To clarify the bio-safety of PAMAM dendrimers, the effects of generation 5 PAMAM dendrimers with amine, hydroxyl or carboxyl groups on immune molecules were explored in this work. Methods: Specifically, the effect of the PAMAM...