Interleukin-2 is a cytokine, a specialized protein manufactured in the body by white blood cells called T-cells, also known as CD4 cells. As an interleukin, it acts as an immune system signaling molecule that relays information from cell to cell. The synthesis of interleukin-2 is stimulated by the presence of an infection. Its mechanism of action is to support the immune system by acting as an immune modulator. This is achieved by increasing the production and count of CD4 cells to fight the infection.
As one might expect, a low CD4 cell count may indicate the onset of disease. Invading viral molecules, or antigens, attack and permeate these cells through their membranes. The antigens then multiply with the goal to replicate and spread the virus to other cells. A healthy immune system responds by first detecting the invading microbes through antigen receptors that reside on the surface of lymphocytes. As antigens bind to receptor sites, the production and release of interleukin-2 is triggered. However, if immunity is impaired, this process may be inhibited.
In the United States, the Food and Drug Administration has approved the use of interleukin-2 to treat certain cancers; such as melanoma, lymphoma, and kidney cancer. In addition, interleukin-2 therapy may be beneficial in treating some chronic viral infections. However, its use in treating human immunodeficiency virus (HIV) is problematic and not yet approved. This is primarily due to the fact that unless antiretroviral drugs are given as a control factor, interleukin-2 therapy can drive HIV viral replication by up to six times the level it was prior to treatment.
Interleukin-2 must be administered intravenously since it is a protein that would otherwise be digested if taken by mouth. Most often, it is given as subcutaneous injections, twice a day at five-day intervals. However, sometimes interleukin-2 is administered by the bolus method, which involves the dose being given by continuous intravenous therapy (IV) over the course of a few hours.
Not everyone is a candidate for interleukin-2 therapy. For instance, those who take immunosuppressive drugs, such as cortisone or prednisone, will not likely experience any benefit from interleukin-2 therapy. In addition, treatment with interleukin-2 may worsen certain immune disorders, such as diabetes. Other factors that may rule out interleukin-2 therapy for certain individuals is a decrease in neutrophil production and thyroid functioning.
Interleukin-2 therapy also involves various side effects, which is why patients receiving high doses are usually admitted and monitored in a hospital. Common side effects include nausea, fatigue, confusion, depression, irritability and insomnia. Capillary leak syndrome may occur at injection sites, which can promote fluid retention, swelling, weight gain and low blood pressure. High dose interleukin-2 therapy may also cause tachycardia (fast heart beat) and affect functioning of the liver, lungs or kidneys.
Interleukin-2 is available as the generic drug Aldesleukin, or under the trade name of Proleukin. Eligibility for interleukin-2 therapy is determined by a health care practitioner after a review of all existing medical conditions and current treatments. If qualified, regular check-ups are necessary to monitor and manage any side effects that may develop.