Trillions of different antibodies and receptors can be formed. Each cell carries thousands of copies of a single, specific receptor. Stimulation of the cell-surface receptor is the first step in activating each type of cell.
Antibodies consist of a light chain and a heavy chain.
The light chain is formed when the lymphocyte selects one constant gene region, one variable region, and one joining region from among many. The cell links the components, and the information the components convey is translated to form a specific protein. T cells kill infected cells directly and regulate B cell function. Antibodies bind directly to intact antigens that are part of larger structures, such as viruses. T cells bind processed antigen fragments when they are properly presented.