Immune systems, characteristics

The production of N-formylated proteins is a characteristic specific to bacteria and, therefore, an obvious target for the human immune system. It has been shown that professional phagocytes, the first line of defence against invading microorganisms, express receptors that recognise N-formylated peptides [12], and that activation of these receptors mediates migration of... 

The capacity of antibodies to recognize myriads of different antigens in a specific manner is one of the characteristic features of the immune system. Since most antigens of biological interest are proteins, the present... 

Hydrophobically modified HA derivatives,91 obtained through the partial esterification of the HA carboxyl groups with methylprednisolone (45% in HYCp45 and 60% in HYCp60),92 have been deeply studied 93 A key point prior to any in vivo study of the biomaterial is the assessment of the so-called "stealth character" of the species itself. Such characteristic corresponds to be invisible towards the immune system, so that colloids are not recognized as foreign objects by body fluid components, as plasma proteins fibrinogen, BSA and lipidic components.94,95... 

Details on the cellular immune responses occurring following the recognition of xenobiotic haptens as antigens by the immune system are described in chapters 33-35 of this volume. Ultimately, a certain combination of mediators is selectively activated and subsequently helps determine and differentiate the characteristic immune response (e.g., Thl vs. Th2). For example, dermal sensitizing chemicals (e.g., oxazolone and dinitrochlorobenzene) elicit a higher proportion of Thl cytokines such as IFNy and... 

In vitro exposure is most straightforward for direct immunotoxicants. However, materials that require biotransformation would require special culture systems (e.g., culture in the presence of S9). Furthermore, an additional limitation of in vitro methods would be the physicochemical characteristics of the test material, which may interfere with the in vitro system. Such characteristics may include the need for serum, effects of vehicle on cells (such as DMSO), and chemical binding to cells. In vitro systems do not take into account the interactions of the different components and it is difficult to reproduce in vitro the integrity of the immune system. Finally, in vitro systems do not account for potential neuro-immuno-endocrine interactions. 

Table 15.8 lists numerous types of drugs that are immunosuppressive and describes their immunotoxic effects. Several classes of drugs that characteristically depress the immune system are fiirther discussed in the next section. 

The adaptive immune system is much more sophisticated than the innate immune system. Three characteristics reflect this degree of sophistication ... 

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