“…These neoplastic proliferations of one or more of the cellular components of the immunological system have been shown to have several features in common, namely: (1) the proliferation of cells concerned in immunological responses; (2) immunodeficiences due to defective synthesis of antibodies, defective cellmediated (delayed) hypersensitivity or both (Miller, 1962;Good et al, 1962;Fahey et al, 1963;Cone and Uhr, 1964;Aisenberg, 1968); (3) the production of monoclonal immunoglobulins (" M " components) which is a feature of myelomatosis and Waldenstrom's macroglobulinaemia as well as of many cases of chronic lymphocytic leukaemia (CLL) and well differentiated (diffuse or follicular) lymphocytic lymphoma (Haller, 1966;Krauss and Sokal, 1966) and of cases of mixed lymphoid and plasma cell proliferation (Saunders et al, 1969); and (4) the well-recognized existence of cases with features intermediate between two or more of the diseases in the group (Vtander and Johnson, 1960;Weinreich and Krey, 1968;Zlotnick and Robinson, 1970;Galton et al, 1968;Forte et al, 1970;Jaeger and Lapp, 1970;Naidu and Rosner, 1971). An abnormal lymphocyte population, non-responsive or slowly responsive to mitogens, has been demonstrated in chronic lymphocytic leukaemia (CLL) (Quaglino and Cowling, 1964;Oppenheim et at., 1965;Thomson et al, 1966;Schrek, 1967;Lawler et al, 1968;Rubin et al, 1969).…”