LIFE SCIENCE

Detailed explanation-1: -The thymus gland is the primary lymphoid organ for lymphocyte development. The red bone marrow produces B-lymphocytes (B cells) and T lymphocytes (T cells). B cells achieve immunocompetence (ability to recognize a specific antigen) in bone marrow. T cells migrate to the thymus gland, where they become immunocompetent.

Detailed explanation-2: -B cells change their location with their stages of maturation, each location providing the microenvironment suitable for the B cell at that life stage. Stem cells produce lymphoid progenitors and pro-B cells in the marrow just under the bone. Developing B cells move toward the center of the marrow as they mature.

Detailed explanation-3: -In reference to lymphocytes, immunocompetence means that a B cell or T cell is mature and can recognize antigens and allow a person to mount an immune response.

Detailed explanation-4: -These lymphocytes develop immunocompetence in the primary lymphoid organs: thymus, for the T lymphocytes and bursa of Fabricius (in birds), on its equivalent (in mammals), for B lymphocytes.