Equine CXCL13 (C-X-C motif chemokine ligand 13), also known as BCA-1 (B-cell–attracting chemokine 1), is a homeostatic chemokine belonging to the CXC chemokine family that plays a critical role in B-cell migration, lymphoid follicle formation, and humoral immune responses. In horses (Equus caballus), CXCL13 is produced primarily by follicular dendritic cells, stromal cells, and macrophages within secondary lymphoid tissues, including the lymph nodes, spleen, and mucosal-associated lymphoid tissues. CXCL13 signals through the chemokine receptor CXCR5, which is expressed on B lymphocytes and T follicular helper (Tfh) cells, directing their migration into lymphoid follicles and germinal centers, where antibody-producing B cells undergo proliferation, affinity maturation, and differentiation into plasma cells. In equine health, CXCL13 contributes to the development of protective humoral immunity following infection or vaccination and is involved in the organization of lymphoid tissues during inflammatory responses. Horses also serve as valuable animal models for neuroinflammatory and infectious diseases, and CXCL13 has been investigated as a biomarker of central nervous system inflammation in equine neuroborreliosis (Lyme neuroborreliosis), where elevated CXCL13 levels in cerebrospinal fluid are associated with B-cell recruitment and intrathecal immune responses, providing insights relevant to both equine neurology and human neuroinflammatory disease research.