REN and hydrops fetalis: Studies indicate that activated neurohumoral mechanisms modulate immune cells in HF (70, 71): From an AISI perspective, evidence shows that Renin-Angiotensin-Aldosterone System activation in HF patients leads to angiotensin II-mediated regulation of macrophage phenotypes by promoting M2 macrophage polarization; this stimulation may influence Th1/Th2 lymphocyte balance, induce lymphocyte apoptosis, and ultimately reduce lymphocyte counts (70, 72).