Immunological and genotypic analysis of human T gamma-lymphoproliferative disorders

T gamma-lymphoproliferative disorders (T gamma-LPD) are rare diseases characterized by expansion of circulating elements with resemblance to large granular lymphocytes (LGL). We have studied 12 patients with T gamma-LPD. Morphological evaluation revealed 79-88% of LGL in non-adherent peripheral blood lymphocytes as assessed by light and electron microscopy. The most common features of the membrane phenotype included expression of T3, HNK-1 and AB8.28 (anti-Fc gamma); other surface markers of LGL (OKM1, B73.1, N901) were variably expressed or absent. Patients' LGL usually had little or no NK activity, with the exception of two patients who had values comparable to those of normal donors; in addition, cell preparations from all patients mediated antibody-dependent cellular cytotoxicity. The recent availability of the T cell receptor beta chain probes allowed us to investigate the lineage and the clonality of T gamma-LPD. Of the 12 patients analyzed, 10 displayed clonal rearrangements of T beta locus and expression of the T3 antigen, whereas the two remaining cases displayed a germ-line configuration of the T beta gene and no expression of the T3 antigen. We suggest that individual T gamma-LPD cases represent the clonal expansion of cells frozen at different stages of differentiation/activation within an individual hematopoietic LGL/NK lineage. These data suggest that either a subset of LGL or a particular step of differentiation may be related to the T cell lineage.