3.4.6 RNA Vaccine .....................................................................................53

3.5 Conclusion......................................................................................................53

References................................................................................................................54

3.1

INTRODUCTION

We are continuously exposed to pathogens, many of which could cause serious

disease. If it were not for our immune system, that is constantly surveying the

environment, recognizing pathogens, and defending us from attack, we would

succumb to infection more frequently. This is a formidable task given the large

number and diversity of pathogens. The immune system needs not only to recognize

them but also to distinguish one from the other. Moreover, some pathogens share

molecular features with humans and so the immune system has the other major

challenge of distinguishing “foreign” from “self.” This chapter will describe the

toolkit and strategies that the immune system uses to accomplish this daunting task.

The response to a pathogen takes place in two stages, depicted schematically in

Figure 3.1. The first, a “rapid-acting” innate immune system, recognizes the threat and

swiftly triggers a response, although the recognition and therefore the response is not

specific to the pathogen. However, the importance of this phase cannot be overstated,

since, not only the intensity, but also the quality of the second or adaptive phase

FIGURE 3.1 The immune system. This figure is a schematic representation of the response

of the immune system to a foreign organism. Starting from the rapid response of the cells of

the innate immune system, information about the risk is conveyed by the bridging elements

(macrophage and dendritic cells) to the adaptive immune system that mounts both a humoral

(production of antibodies by the B cells) and a cellular (T cells that can either support the

humoral response or produce cytotoxic molecules) response that attacks the pathogen with

exquisite specificity.

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Bioprocessing of Viral Vaccines