OPC UA uses Symmetric and Asymmetric Signatures to address Integrity as a security objective. The Asymmetric Signatures are used in the key agreement phase during the Secure Channel establishment. The Symmetric Signatures are applied to all other Messages including PubSub messages.
OPC UA relies upon the site CSMS to protect Integrity on the network and system infrastructure. OPC UA relies upon the PKI to manage keys used for Asymmetric Signatures which is then used to establish symmetric session keys.