CXCL13 and systemic lupus erythematosus: CXCL13 levels were upregulated in synovial tissue (54) and plasma (55) from patients with rheumatoid arthritis, in serum (56) and plasma (57) from patients with systemic lupus erythematosus, in CSF from patients with multiple sclerosis (58, 59) and in serum from patients with myasthenia gravis (60).