CXCL13 and myeloid sarcoma: The issue of “a potential effect of pathological transfer of CXCL12 or CXCL13 from blood to CSF” was addressed by Krumbholz by separately analyzing MS patients with a “disrupted blood–brain barrier” defined in their work by a ratio of CSF to serum albumin(i.e., Qalb) of greater than 0.0074.