The special lymphatic vessels in the lining of the small intestines are the .

The lymphatic system begins in the tissues as .

Lymphocytes that attack foreign cells or body cells infected by viruses are called .

Cells that represent the "first line" of cellular defense against pathogens are the .

Antibodies are produced and secreted by .

An immunization where antibodies are administered to fight infection or prevent disease is .

Cytotoxic T cells are responsible for the type of immunity referred to as .

Immunity that appears following exposure to an antigen as a consequence of the immune response is referred to as .

The types of cells that inhibit the responses of other T cells and B cells are called cells.

Before B cells can respond to an antigen, they must receive a signal from cells.