The line of defense is referred to as the immune response. 2. are large, Y-shaped proteins that recognize and bind to antigens. 3. The lymphatic system produces leukocytes called . 4. cells and cells are the two major types of lymphocytes. 5. Lymphocytes recognize and help destroy in body fluids and cells. 6. Memory B and T cells help protect the body from re-infection by pathogens that have infected the body in the past, a protection called . 7. The immune response inv