What does the immune system monitor continuously to ensure the protection of the body?

The immune system monitor continuously the lymphocyte cell levels in order to ensure the protection of the body. These cells are a type of white blood cells that are important in determining the specificity of the response of the body to foreign substances and infectious microorganisms. This group of cells include the T cells, B cells and the natural killer cells. These are produced in the bone marrow and are transported to the lymphatic systems like the thymus, spleen and the lymph nodes. The NK cells function in cytotoxic innate immunity or the cell-mediated ones. T-cells would function by connecting to virus antigens on the outside of a cell that is infected while B-cells would connect to the virus directly in its surface.