Mobile agent is a progrant that can migrate from a machine to another in a network and perform tasks on machines that provide agent hosting capability. The agent can clone itself in order to increase system robustness and efficiency. The clone operation creates multiple instances of an agent to run on different machines. However, increasing agent population size, with cloning operation, will increase resource demands in the network, which would indirectly affect network performance. When, the mobile agents operate in a dynamic and distributed environment, it is difficult to estimate a priori the appropriate number of agents allowed to be spawned in the network. This paper focuses on the problem of dynamic regulation of mobile agent population size in a distributed system, and proposes an approach that takes inspiration from the immune system concept.