Class II human leucocyte antigen DRB1*11 in hairy cell leukaemia patients with and without haemolytic uraemic syndrome.

Frequencies of human leucocyte antigens (HLA) were determined in 287 classic hairy cell leukaemia (HCL) patients. With respect to both population (n = 287) and allele (2n = 574) frequency respectively, the most common HLA class I and II antigens expressed were HLA-A02 (49·1% and 28·6%), HLA-B07 (21·3% and 11·1%), HLA-C07 (46·7 and 28·2%), HLA-DQB103 (62·7% and 37·3%), HLA-DRB111 (30·0% and 16·0%) and HLA-DRB401 (45·3% and 29·6%). In comparing 6-14 databases of control Caucasians to 267 Caucasian HCL patients, only HLA-DRB111 was consistently over-represented in HCL, 31·1% of patients vs. 17-19·9% of controls (P = 0·0055 to <0·0001) and 16·5% of alleles vs. 6·5-12·3% of control alleles (P = 0·022 to <0·0001). HLA-DRB111 is a known risk factor for acquired thrombotic microangiopathy. Anti-CD22 recombinant immunotoxin BL22 in HCL was associated with a 12% incidence of completely reversible grade 3-4 haemolytic uraemic syndrome (HUS), mainly during the second or third retreatment cycle. Of 49 HCL patients receiving ≥2 cycles of BL22, 7 (14%) had HUS and HLA-DRB111 was expressed in 71% of 7 with HUS compared with only 21% of 42 without (P = 0·015). These data suggest that DBR111 may be a marker for increased susceptibility to HCL and, among HCL patients, could be a risk factor for BL22-induced HUS.