Immune activation in chronic heart failure.

In chronic heart failure (CHF), activation of the immune system occurs, which results in the production and release of proinflammatory cytokines, activation of the complement system, and production of autoantibodies. Thus, it is important to consider CHF as a systemic illness, not just a disease of the "pump." Immune activation in CHF can be divided into 2 broad categories: (1) immune activation by direct antigenic stimulation, or (2) immune activation secondary to cardiac injury that exposes "new antigens" capable of triggering an immune response against the heart. Cytokines are essential for the propagation and magnification of the immune response. They are involved in recruiting cells to the area of inflammation, stimulating cell division, proliferation, and differentiation. Circulating levels of the cytokine tumor necrosis factor-alpha (TNF-alpha) are increased in patients with CHF. Thus, cytokines are key elements of immune activation. Studies to investigate the role of increased TNF-alpha levels have failed to show a correlation with worsening CHF, most likely because the immune system is redundant, and other proinflammatory cytokines (interleukin [IL]-1 and IL-6) are known to be elevated in CHF. Approaches showing promise are those that enhance the natural anti-inflammatory response (eg, intravenous immunoglobulin (IVIG), immunoadsorption, immune-modulation therapy [IMT]), rather than those that specifically target a single type of cytokine. The mechanism by which IVIG modulates the immune system is unknown. Immunoadsorption involves the removal of specific antibodies from circulation. IMT works by inducing apoptosis in a sample of blood, which is then administered back to the patient. The immune system reacts by removing the apoptotic cells, thus inducing a systemic anti-inflammatory response.