lymphoïde

Lymphoïde is the French term corresponding to lymphoid in English. It is an adjective and, in some contexts, a noun used to describe tissues, cells, and processes related to the lymphatic and immune system. In medical and biological usage, lymphoïde denotes anything derived from or composed of lymphocytes or lymphoid tissue, in contrast with myeloïde (myeloid) components.

Anatomically, the lymphoid system comprises primary and secondary lymphoid organs. Primary lymphoid organs include bone marrow and the thymus, where lymphocytes develop and mature. Secondary lymphoid organs – such as lymph nodes, spleen, and mucosa-associated lymphoid tissue (MALT) including gut-associated lymphoid tissue (GALT) – are sites where antigen encounters initiate immune responses. Lymphoid tissue is rich in lymphocytes (B cells, T cells) and antigen-presenting cells and forms nodules or follicles in various mucosal and lymphoid sites.

Clinically, the term lymphoid is used to describe cells and neoplasms of the lymphoid lineage, including B-cell and T-cell lymphomas and leukemias. Immunophenotyping uses markers such as CD19/CD20 for B cells and CD3 for T cells to identify lineage. Lymphoid components are contrasted with myeloid components in hematopoiesis and pathology. The concept is central to understanding adaptive immunity, vaccine responses, and many diseases affecting the immune system.