1. Cattle have a complex immune system that produces lymphocytes and antibodies to recognize and fight pathogens. The immune system response is either humoral, involving antibodies, or cell-mediated, using effector cells. 2. The immune system has primary organs like the thymus, bone marrow, and Peyer's patches that produce lymphocytes, and secondary organs like lymph nodes and spleen that respond to pathogens. 3. Immunity can be innate, involving physical and chemical barriers, or acquired through adaptive immune responses using memory cells and targeted antibodies after exposure to antigens.