Lymphocytes are a type of white blood cell produced in bone marrow that play a crucial role in your immune system. There are several types—called T cells, B cells, and natural killer (NK) cells—that ...

Human cancer under a microscope. The black dots on the right of the image are lymphocytes which are trying to get at the tumor, but are being stopped by cancer-associated fibroblasts. Disclaimer: AAAS ...