T cells: Cells of the immune system that recognize "foreign" substances in the body and then help launch an attack.

Thrombocytopenia: A decrease in the number of platelets in the blood.

TNF: A protein produced by the immune system that improves the immune response and that can destroy some types of cancer cells.

Tumor: An abnormal mass of tissue that results from excessive cell division. Tumors perform no useful body function. They may either be benign (not cancerous) or malignant (cancerous).