Induction of mucosal immune responses in the human genital tract.

Mucosae of the female and male genital tracts are the portals of entry for sexually transmitted diseases (STDs) of viral, bacterial, and parasitic origin; worldwide, V120 000 000 cases of STDs are reported annually, but the true incidence is probably much higher. Infection with human immunode¢ciency virus (HIV) is no exception: epidemiologic data indicate that worldwide, 70^ 90% of all HIV infections are acquired by heterosexual transmission [1]. This route has the most rapidly rising incidence of new infections, especially among women, who are infected at higher rates than men. Thus, induction of immune responses at the major portals of entry of STD agents and HIV may be important for protection against these infections. Studies performed in animal models and in humans have convincingly demonstrated that the mucosal and systemic compartments of the immune system display a signi¢cant degree of mutual independence [2]. Immunoglobulins (Ig) present in external secretions or systemic £uids are represented by molecules of di¡erent physicochemical and biological properties. In external secretions of humans and many mammalian species, the dominant Ig is secretory IgA (S-IgA), consisting of polymeric IgA (pIgA) with J chain, and secretory component (SC) derived from epithelial cells [3]. However, secretions of the female and male genital tracts di¡er from other external secretions (e.g., saliva or milk) as well as from plasma in the proportion of Ig isotypes and forms.