lymphoide

Lymphoide is an adjective used in anatomy and histology to describe tissues, organs, or cells that are related to the lymphatic system or resemble lymphoid tissue. In English, the corresponding term is lymphoid, and in some other languages forms such as lymphoïde may be used.

Lymphoid tissue is a key component of the immune system and consists primarily of lymphocytes, along with supporting stromal cells and immune accessory cells. Lymphoid tissues and organs are categorized as primary or secondary. Primary lymphoid organs, such as the bone marrow and thymus, are sites where lymphocytes develop and mature. Secondary lymphoid organs, including lymph nodes, the spleen, tonsils, and mucosa-associated lymphoid tissue (MALT), provide environments for antigen encounter, lymphocyte activation, and initiation of adaptive immune responses.

Lymphoid cells arise from hematopoietic stem cells in the bone marrow. B lymphocytes mature in the bone marrow, T lymphocytes mature in the thymus, and natural killer (NK) cells arise from the lymphoid lineage. These cells coordinate immune defense through antigen-specific and non-specific mechanisms, including antibody production, cytotoxic responses, and regulation of other immune cells.

Lymphoid-related terms also apply to pathology. Lymphoid neoplasms, such as lymphoid leukemias and lymphomas, originate from malignant lymphoid cells and are classified by lineage (B or T) and by specific molecular features. Understanding lymphoid tissues and their development is fundamental to immunology, hematology, and pathology.