Human leucocyte antigen class I and killer immunoglobulin‐like receptor expression patterns in T‐cell large granular lymphocyte leukaemia

Summary T‐cell large granular lymphocyte leukaemia (T‐LGLL) is often associated with suppression of haematopoiesis through unknown mechanisms. Killer immunoglobulin‐like receptors (KIRs) binding human‐leucocyte antigen (HLA)‐I in an allele‐specific manner are frequently expressed by T‐LGLL cells. HLA‐I genotyping was performed in seven T‐LGLL cases in which the neoplastic cells were known to express a single KIR isoform (CD158a, CD158b or CD158e). Five cases showed absence of the cognate HLA‐I antigen for the expressed KIR isoform, resulting in KIR/HLA‐I ‘mismatch’. Cytopenias occurred in all five ‘mismatch’ patients but not in two patients with ‘match’, suggesting that KIR/HLA‐I mismatch may contribute to the suppression of haematopoiesis.