IMMUNOLOGY

Detailed explanation-1: -Primary Lymphoid Organs refer to Immune System Organs in which Lymphocytes form and mature while Secondary Immune Organs refer to Immune System Organs that maintain mature naive Lymphocytes and initiate an adaptive Immune response. This is the major difference between Lymphoid Organs of Primary and Secondary origin.

Detailed explanation-2: -Bone marrow, a primary lymphoid organ, is a spongy tissue found in the bones. It is the site for the production of precursors of T cells, and production and maturation of B cells. These cells are then transported to other organs and tissues via blood to carry out their function.

Detailed explanation-3: -There are estimates that about 12% of all lymphoid cells in the human body are found in the bone marrow at any given time (2% in the peripheral blood). Enormous numbers of T lymphocytes migrate to the bone marrow and partly return later to the blood. Many of these lymphocytes are memory CD4+ and CD8+ T cells.

Detailed explanation-4: -There are two major types of lymphocyte: B lymphocytes, which mature in the bone marrow; and T lymphocytes, which mature in the thymus. The bone marrow and thymus are thus known as the central or primary lymphoid organs.