Microparticles and the hygiene hypothesis.

Departing from the functional parallelism that undoubtedly exists between the nervous and immune system, we suggest that the latter also counts with means for information exchange that may result in a mutual influence of immune processes between nearby individuals. Our concept relies on a molecular interface that is composed and, at the same time, interfered or modulated by the vast number of environmental agents from the surrounding milieu. We highlight the possibility that microparticles, previously shown to act as mediators of the transfer of receptors and other relevant immune molecules between distant cells, may represent a minor immune medium. In line with this argument, we envisage a potential role for the suggested interindividual immune link particularly in marginal conditions, such as those that shaped life in historical population centers or even in currently undeveloped countries. We speculate that overcrowding and unhygienic habits as dominant conditions may provide a suitable framework for the interconnection of individuals by means of their respective body wrapping microenvironments. As a corollary, we propose that collective means of defense may belong to the toolbox with which the immune system faces exceptional challenges. In the context, it seems highly suggestive to establish a link with the hygiene hypothesis. In this scenario, modern lifestyle appears as an interfering factor by dismantling the necessary conditions for the emergence of the immunological interface. Therefore, it is not implausible to confer to this modern 'immunological miscommunication' a role in current trends concerning the incidence of autoimmunity, allergy and chronic inflammation.