The human body has a very effective Immune system used to protect the body from dangerous foreign pathogens. This paper aims at studying the immunology and understanding how it works, it also shaded light on the usage of the immunology principles in the computer network security. It also suggested a new network security model which detects attacks that invades the LANs. This study based on human immune system (IS). This model help protecting the datalink layer by suggesting solution to detect the foreign frames in computer network traffic. In this model, the frame format is changed in a way that prevents the sender from sending his MAC address, and he send a unique identifier (ID) instead. Moreover, a special network switch will replace the sender ID with the corresponding MAC address and forward the packets to their right destination.