Furthermore, the airways are highly populated by dendritic cells (DCs) that clear microorganisms through phagocytosis, and there are large quantities of the immunoglobin IgA that function to bind toxin and viral particles as well as impede bacterial invasion of epithelial cells (Nicod, 2005). While upper airway DCs may play a role in preventing cryptococcal yeast cells from getting deep within the lungs, there is no evidence that airway IgA is required for prevention of cryptococcal infection. However, it is intriguing to speculate whether upper airway DCs may represent an alternative route of primary infection for the immunocompromised.