Immune response antigens, structure

Rotavirus enterotoxin protein NSP4 fused to CTB Potato Fusion proteins assembled into cholera holo-toxin-like structures that retained enterocyte-binding affinity Orally immunized mice generated levels of serum and mucosal antibodies specific for the native antigen. Induced TH1 immune response. 63,64... 

Two different systems are involved in the immune response. The innate immune system is based on receptors that can distinguish between bacterial and viral surface structures or foreign proteins (known as antigens) and those that are endogenous. With the help of these receptors, phagocytes bind to the pathogens, absorb them by endocytosis, and break them down. The complement system (see p. 298) is also part of the innate system. 

The structures of oligosaccharides linked to these proteins can be complex and many of them contribute to antigenicity, the ability of the cell surface to elicit an immune response. 

Despite their popularity, aluminium-based adjuvants suffer from several drawbacks. They tend to effectively stimulate only the humoral arm of the immune response. They cannot be frozen or lyophylized, as either process promotes destruction of their gel-based structure. In addition, aluminium-based products display poor or no adjuvanticity when combined with some antigens (e.g. typhoid or Haemophilus influenzae type b capsular polysaccharides). 

The materials capable of stimulating the lymphoid tissues to produce antibodies are termed antigens and comprise bacterial and viruses as well as some smaller molecular entities. However, the response is not to the intact organisms but rather to some specific parts which have characteristic three-dimensional structures, the epitopes, and this sensitivity to structure is a characteristic feature of the immune response. Once an animal is in contact with an epitope the response can be in the circulatory or humoral system or directly as a cell-mediated response, but it is exquisitely sensitive to the specific antigen and rarely to any other. 

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