Immunogenicity

Immunogenicity is dependent upon foreignness, high molecular weight, and chemical complexity, as well as several other factors. These other factors include the animal's genetic makeup and the susceptibility of the substance to enzymatic degradation. It needs to be stable enough to get to the B/T cells to cause an immune response, but at the same time, it needs to be susceptible to processing within antigen presenting cells, eg macrophages, dendritic cells, etc. If a substance resists processing, it cannot activate T cells, and therefore can not provoke a T cell mediated immune response, and cannot provoke class switching.