Canine 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 central role in B-cell migration and organization of lymphoid tissues. In dogs (Canis lupus familiaris), CXCL13 is primarily produced by follicular dendritic cells, stromal cells, and macrophages within secondary lymphoid organs, 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, guiding their migration into lymphoid follicles and germinal centers where antibody-producing B cells develop. In canine immunity, CXCL13 contributes to germinal center formation, B-cell maturation, and humoral immune responses during infection and vaccination. Elevated CXCL13 expression has been associated with chronic inflammatory and infectious diseases, including canine Lyme disease, where CXCL13 in cerebrospinal fluid has been investigated as a biomarker of neuroborreliosis due to its role in recruiting B cells to inflamed nervous tissue. Because of its importance in B-cell trafficking and lymphoid architecture, canine CXCL13 is studied in veterinary immunology, infectious disease research, and biomarker development, helping to improve understanding of B-cell–mediated immune responses and inflammatory disease mechanisms in dogs.