Studies show the presence of immuno-inflammatory disturbances in individuals with Bipolar Disorders (BD). Increased levels of circulating proteins known as cytokines that promote inflammation have been consistently reported in individuals with bipolar disorders. A particular cytokine referred to as Tumor Necrosis Factor (TNF)-alpha is among those cytokines that have been consistently identified across depressive, manic, and euthymic periods. Disturbances in inflammation however, are not seen in all individual with bipolar disorder. Those individuals with signs of inflammation also often present with higher prevalence of medical disorders that are also associated with inflammation. Those individuals with significant signs of inflammation may respond to anti-inflammatory treatments. In this study, individuals with bipolar depression who exhibit signs of high inflammation will be enrolled and treated with either an anti-inflammatory biologic known as infliximab or placebo (saline).