T‐CELL FEATURES IN HAIRY‐CELL LEUKAEMIA

There have now been reports of four cases of hairy-cell leukaemia (HCL) in which the hairy cells (HCs) formed spontaneous rosettes with sheep erythrocytes (E rosettes) (Advani et al, 1976; Cawley ef al, 1978; Saxon et al, 1978; Hernandez et al, 1978). One of these cases also had B-cell features (Cawley et al, 1978), and we now describe another case with the same combined Band T-cell phenotype. The patient, a 38-year-old woman, presented with splenomegaly without lymphadenopathy, skin rash or thymic mass. A peripheral blood (PB) count showed: Hb 10.7 g/dl, WBC 11.7 x 10y/l and platelets 130 x 10y/l. Differential count was as follows: typical hairy cells 68%, lymphocytes 22%, neutrophils 8%, eosinophils 2%, and monocytes nil. A tartrate-resistant acid phosphatase (TRAP) stain showed some 70% strongly positive cells. The bone marrow (BM) was difficult to aspirate, but on biopsy was shown to be diffusely infiltrated by HCs, and displayed prominent rcticulin fibrosis. The spleen was subsequently also shown to be diffusely replaced by HCs. Electron microscopy ofPB, BM and spleen showed the typical ultrastructure of HCs. Electron microscopy of PB, BM and spleen showed the typical ultrastructure of HCs; initially no ribosome-lamellar complexes were seen, but later a very occasional complex was observed in PB HCs. Surface marker analyses with a panel of markers were performed (Table I). In these early studies, the overlap between the percentage of cells forming E rosettes and those possessing surface immunoglobulin (SIg) clearly indicated that a proportion of HCs had a E+SIg+ hybrid phenotype (or, in more detail, E+SIg+yFc+pFc+C3-). Cytocentrifuge preparations confirmed that many TRAP-positive HCs were forming E and SIg rosettes. Stripping of SIg with anti-Ig antisera had no effect on E-rosette formation which could not therefore be attributeh to SIg with chance specificity for sheep erythrocytes (Brouet & Prieur, 1974). Also, E-rosette formation was inhibited by sodium azide and cytochalasin B. I t was therefore concluded that the E-rosette formation by HCs was a genuine T-cell feature. With regard to the simultaneous B-cell characteristics of the patient’s HCs, the extensive precautions required to demonstrate the intrinsic nature of SIg in HCL have been described previously (Cawley et al, 1978; Burns et al, 1978b) and the restricted light chain expression (A) should be noted. In addition, the HCs were shown, by a microagglutination method (Burns et al, 1978b), to secrete IgG. Subsequent sequential studies showed that the E-rosette forming ability of the HCs became much reduced and the majority of the cells then displayed the E-SIg+ phenotype typical of HCs (Catovsky, 1977; Burns et al, 1978a, b). This type of fluctuation in marker phenotype was also observed in our previous case of HCL with T-cell features (Cawley et al , 1978) which has been carefully followed up over an extended period (full details will be published elsewhere). It is evident that if either of these cases had been studied only during the ESIg+ phase, the case would have been regarded as a simple example of B-cell HCL. No sequential studies were reported for the three cases of HCL with T-cell features reported from other laboratories (Advani et al, 1976; Saxon ef al, 1978; Hernandez et al, 1978); furthermore, Ig synthesis-the definitive B-cell marker-was looked for in only one of these