Humoral immune responses in gingival crevice fluid: local and systemic implications

The oral cavity represents the entry portal for a wide array of antigenic challenges, both transient and more permanent. The more permanent challenges are represented by the substantial bacterial colonization that exists in the oral cavity. This environment presents a variety of niches for the establishment of unique microbial ecologies including the oral mucosa, tongue, tooth surface, and gingival sulcus. Many members of the complex oral microbiota maintain a symbiotic relationship with the host; however, select individual species are clearly pathogens (i.e. Streptococcus mutans and Actinobacillus actinomycetemcomitans) within this environment. For the host to maintain homeostasis within the oral cavity, various immune response systems contribute to controlling the microbial colonization. These systems represent three interrelated entities and include the salivary, systemic (serum) and gingival tissue immune systems (Table 1). This review will focus primarily on the gingival tissue immune system, and gingival crevice fluid (GCF) as the biological material contributing to the local sulcal environment. The oral epithelium represents the only site in the body in which the epithelial barrier is deliberately breached by hard tissues (i.e. cementum, enamel), which must be sealed from the external milieu. Even in gingival health, there is a fluid transudate that flows from the site of this seal, presumably as a mechanical factor is minimizing bacterial accumulation. This fluid also contains a variety of macromolecular components that are derived from serum and the interstitia of the gingiva. The concentration