Any conceivable source(s) of the high energy neutrinos, detected by IceCube, produce a gamma-ray flux which can be observed either directly or after experiencing electromagnetic cascade. I will discuss this interrelation between neutrino and gamma-ray messengers and derive bounds on the characteristics of possible source(s). It will be shown that gamma-ray experiments, such as Fermi and EAS experiments, can provide valuable diagnostics in the study of neutrino sources.