The understanding that the immune system has a role in the pathogenesis of essential hypertension was established over the last few decades, with many different works showing that manipulating the immune system effects blood pressure. Pro-inflammatory cell activation can cause hypertension while anti-inflammatory cell activation restrains it. These activations involve different cell types, cytokine and chemokine secretions, and affect different target organs. Additionally, there is evidence that hypertension itself may affect the immune system. This article reviews the main findings in this area.