present on the B-cell membrane and secreted by plasma cells. Membrane-bound antibody con- fers antigenic specificity on B cells; antigen-specific prolifer- ation of B-cell clones is elicted by the interaction of membrane antibody with antigen Secreted antibodies ci culate in the blood, where they serve as the effectors of hu- moral immunity by searching out and neutralizing antigens or marking them for elimination. All antibodies share struc
body. These organs can be classified functionally nto two main groups. The primary lymphoid organs provide appropriate microenvironments for the development and maturation of lymphocytes. The secondary lymphoid organs rap antigen from defined tissues or vascular spaces and are sites where mature lymphocytes can interact effectively with that antigen. Blood vessels and lymphatic systems connect these organs, uniting them into a functional whole Carried within the blood and lymph and populating the Macrophage Interacting with
