CST4 and fungal infectious disease: Cystatins are important inhibitorsof endogenous and exogenous proteases and are involved in the inflammatoryprocesses and in the innate immune response;42 S-type cystatins play this function in the oral cavity, suppressingsome viral, bacterial, and fungal infections of the oral cavity byinhibiting exogenous cysteine proteinases.43,44 Cystatin C is able to modulate migration of monocytes and T cells.45 All the cystatins can regulate the cathepsinactivity.