Cancer Killers

Our immune system is very important. It protects us from damage causing cells and antigens. Unfortunately, this complex system has some flaws that can be utilized by cancer cells.

When a dendritic cell (immune messenger) encounters a malignant cell, it absorbs some of its proteins and presents them to a T cell (immune soldier). The T cell then finds and attacks all the cells containing the malignant cell's protein, a protein called MHC, and a protein called a co-stimulatory ligand (on switch). Any cells without MHC and the co-stimulatory ligand are ignored by the T cells. This makes it hard for T cells to distinguish normal and cancerous cells. To avoid the T cell the malignant cell can either stop producing MHC or create a co-stimulatory ligand to deactivate the T cell.

To solve this problem, researchers have developed the CAR T cell therapy (chimeric antigen receptor T cell therapy). With this therapy, scientists take normal T cells from the patient's body and supply it with genes that make a synthetic molecule called CAR. This allows the T cell to both detect the antigen and activate itself without the presence of MHC or the co-stimulatory ligand.

To detect a malignant cell, however, the T cell must have an antigen found only on a cancer cell. This is hard to find because all cancer cells stem from our own cells. Healthy and malignant cells display the same antigens. Fortunately, in the case of some leukemia and lymphoma, the disease stems from unnecessary B cells (a type of white blood cell). Since B cells all produce a surface protein called CD19, scientists set the T cells to attack the CD19 protein.

In 2010, scientists tested the T cells targeting CD19 on a leukemic patient. He experienced temporary serious side affects because of an immune system overdrive. Fortunately, one month later, doctors couldn't find any signs of leukemic B cells. Even more promising, six years later, the CAR T cells had multiplied and still protected the body from B cells.

This method of targeting cells with specific proteins has led to and innovation can help thousands of people suffering from leukemia. Likewise, it can help millions of other people in the future.