BTK and lymphoma: Many therapies commonly used in the treatment of lymphomas, such as cytostatic agents (fludarabine and bendamustine) [7,8,9], B-cell-depleting therapies (anti-CD20 monoclonal antibodies) [10,11], Bruton kinase (BTK) inhibitors [12,13] and chimeric antigen receptor (CAR) T-cell therapy [14,15], might cause severe and long-lasting immunosuppression.