The roles of salivary secretory IgA on the development of oral candidiasis

Oral candidiasis, an opportunistic fungal infection mainly caused by <i>Candida albicans</i>, is highly prevalent in immunocompromised individuals. Saliva acts as the oral cavity's first line of defense, with secretory immunoglobulin A (sIgA) as its key specific immune component. In this review, we systematically clarify sIgA's multifaceted roles in oral immunity and its significance in the pathogenesis, progression, and management of oral candidiasis. We detail sIgA's biological characteristics (synthesis, secretion) and core mechanisms: immune exclusion (inhibiting fungal adhesion/invasion), virulence factor neutralization, biofilm interference, and immune regulation. We also explore sIgA-<i>C. albicans</i> interactions, including antigen recognition, hyphal transition inhibition, and fungal evasion strategies (protease degradation, antigenic variation). Clinical evidence shows that compromised salivary sIgA levels/function-due to systemic diseases (e.g., HIV/AIDS, Sjögren's syndrome), aging, radiotherapy, or immunosuppression - correlates with increased susceptibility and severity of oral candidiasis, with functional quality being equally crucial as quantity. Given conventional antifungal limitations, we discuss sIgA-based interventions (recombinant sIgA passive immunization, mucosal vaccines, probiotic adjuvants). In conclusion, salivary sIgA is critical to maintaining oral mucosal homeostasis against <i>C. albicans</i>, and enhancing its function offers promising avenues for preventing and treating oral candidiasis.