IMMUNOLOGY

Detailed explanation-1: -The key primary lymphoid organs of the immune system are the thymus and bone marrow, and secondary lymphatic tissues such as spleen, tonsils, lymph vessels, lymph nodes, adenoids, and skin and liver.

Detailed explanation-2: -Specialised animal cells include red blood cells, sperm, eggs, nerve cells, muscle cells, ciliated cells, and villi.

Detailed explanation-3: -Adaptive immune responses are carried out by white blood cells called lymphocytes. There are two broad classes of such responses-antibody responses and cell-mediated immune responses, and they are carried out by different classes of lymphocytes, called B cells and T cells, respectively.