Lymphocyte

A type of leukocyte. Lymphocytes are made in lymph nodes and circulate in both in the bloodstream and in the parallelcirculating system, the lymphatic system. Lymphocytes are divided into 2 principal groups, T cells and B cells, based on their surface molecules, as well as their function. The two types of lymphocytes are involved in immune response. T cells attack invading viruses and bacteria, while B cells produce antibodies.