Immune response physical barriers

As opposed to the DNA vaccination via PMGT, where DNA is introduced directly into cells by gold particles, the extracellularly-delivered DNA after needle and syringe injection has to overcome the physical barrier of the cell membrane via a passive and rather ineffective process. This very inefficient DNA uptake is most likely the reason for the large quantities of DNA needed to induce immune responses in vivo, especially in larger animals and human. Increased gene expression in vivo can be achieved by... 

Although the stratum corneum acts as a simple physical barrier to outside influences, skin tissue as a whole is very active. It is crucial in maintaining the body s homeostasis, its essential steady-state environment. Skin maintains temperature and balance of electrolytes, the dissolved salts in internal body fluids. It is metabolically active and participates in hormonal and immune regulatory processes. More than serving as a passive barrier, it is proactive in response to xenobiotic insults and can be damaged in the defensive process by developing rashes and other symptoms. 

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