Abstract
Immune system is one of the most important biological systems in every living organism. The defensive mechanisms incurred by the immune system protect the organism from potential threats or the harmful substances caused by the foreign pathogens such as parasites, bacteria and virus. For human and many vertebrates, the complicated immune system can basically be categorized into two main subsystems: the innate and adaptive immune system. In this study, based on the time-course microarray data of zebrafish in its primary and secondary infection by C. albicans, we constructed two zebrafish intracellular PPI networks for the primary and secondary infection, respectively. By inspecting the hub proteins of each network and by comparing the significant changes of the number of linkages between the two constructed PPI networks, we identified the process of apoptosis as one of the main functional modules that is activated for the primary infection and inhibited for the secondary infection. Based on our findings, we postulated that pathogen-induced apoptosis is relatively more active during primary infection since immunity responses triggered by zebrafish under primary infection are not efficient enough. For host-induced apoptosis, however, the immunological memory enables the host immune system to response to the pathogen more precisely during secondary infection. Hence, apoptosis is activated during primary infection but inhibited during secondary infection. Our in silico analyses help pave the foundation for further investigation on the interesting roles played by apoptosis on innate and adaptive immunity for zebrafish. We believe that such insights could lead to therapeutic advances and drug design for the never-ending battle against infectious diseases.