Figure 3.

Effect of the particle size on the immune response. Particles 20–200 nm in diameter efficiently enter the lymphatic system, with particles smaller than 50 nm being more efficiently transported than those larger than 100 nm. Particles smaller than 49 nm in diameter induce a stronger T CD8 cell response, and particles larger than 50 nm promote a stronger CD4 T cell response. Overall, the strength of the T cell response inversely correlates with the particle size and antibody response, which seems to be stronger with larger particles.