Five Mendelian traits conferring susceptibility to a single, weakly pathogenic pathogen have been elucidated at the molecular level. Two studies identified new genes involved in host defence (XLP, EV), whereas the other three provided insight into the function of known genes in humans (MSMD, MAC/PFC, invasive pneumococcal disease). Many other similar clinical syndromes, such as isolated chronic mucocutaneous candidiasis (Lilic 2002), herpes simplex encephalitis (Dupuis et al 2003), and HHV8-driven idiopathic Kaposi's sarcoma (Guttman-Yassky et al 2004), are probably also Mendelian, but molecular genetic investigations are required to confirm this hypothesis. More common infectious diseases, caused by more virulent micro-organisms, may also result from Mendelian disorders, as illustrated by the recent demonstration that tuberculosis (TB) is a Mendelian disorder, at least in some children (Alcais et al 2005). These 'experiments of nature' demonstrate the existence of specific interactions between certain immune genes and pathogenic microbes. In natural conditions of immunity and infection—the hallmark of the human model (Casanova & Abel 2002, 2004b) — these genes appear to be non-redundant for protective immunity to specific pathogens. The mutations reviewed here have provided important insight into the functioning of the immune system, as they have revealed ecologically relevant and evolutionary selected specific interactions between certain human genes and microbial pathogens.
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The term vaginitis is one that is applied to any inflammation or infection of the vagina, and there are many different conditions that are categorized together under this ‘broad’ heading, including bacterial vaginosis, trichomoniasis and non-infectious vaginitis.