CD4 and interstitial nephritis: Zaidan et al. [31] reported on a patient of IgG4-related systemic disease with tubulointerstitial nephritis; striking features were the abundance of interfollicular plasma cells and CD4+ T-cells in germinal centres of lymph nodes and the dramatic response to rituximab point to possible roles of Tfh cells in enhancing a skewed B-cell terminal maturation and of CD20+ B cells in disease progression.