CD19 and head and neck squamous cell carcinoma: As summarized in Fig. 1a and Additional file 1: Table S2, the percentage of CD3−/CD19+ B cells in patients with non-recurring SCCHN (n = 23) was significantly lower compared to that of healthy volunteers (Ctrl) already before start of RCT at t0 (t0 vs. Ctrl: 8.88% vs. 10.83%, p ≤ 0.05), and remained low until 3 months after RCT at t2.