A quantum Heisenberg spin chain with anisotropic coupling and all-to-all interspin interaction has been analyzed using Bose statistics. In (JSP 116, 1435 (2004)) the existence of a disconnection threshold in the classical version has been demonstrated. The question of finding a quantum signature of the classical disconnection border has been addressed here. A quantum disconnection border, motivated by purely quantum considerations is given. The presence of a disconnection border allows the study of Macroscopic Quantum Phenomena, like Macroscopic Quantum Tunneling and Macroscopic Quantum Coherence. Indeed, below this border, at variance with the classical case, the total magnetization can flip its sign through Macroscopic Quantum Tunneling. We also discuss the dynamical relevance of such border with respect to the magnetic reversal times, in the light of the results found in the classical model.