T-cell receptor genes expression in B-cell leukaemias

T-cell receptor beta gene rearrangements in leukaemic B-cells from patients with chronic lymphocytic leukaemia: association with chromosome 6 deletions

Rearrangement of immunoglobulin genes is a characteristic finding in normal B-cells and in leukaemic cells of B-cell origin. In some leukaemic cells simultaneous cross-lineage rearrangement of immunoglobulin- and T-cell receptor (TcR) genes occur. We have analysed TcR beta gene rearrangement in 100 patients with B-cell chronic lymphocytic leukaemia. All samples expressed CD5, CD19 and CD20 and six patients had rearrangements of both immunoglobulin and TcR beta genes. Analysis of gene expression in cells with TcR beta gene rearrangement indicated production of truncated TcR beta transcripts but no expression of the T-cell markers CD3, CD4, CD8, TcR alpha beta or delta on the cell surface. Three of the patients with both Ig and TcR beta rearrangement (50%) were 44 years or younger at diagnosis and cells from three such patients expressed IgG. Three of the six patients had a terminal deletion of the long arm of chromosome 6 with different breakpoints, with or without other chromosomal abnormalities, whereas 6q deletions were found in 4/94 patients without TcR beta gene rearrangement (4.3%) (P = 0.001). This study indicates a correlation between TcR beta gene rearrangement and deletion of chromosome 6q.

Kappa light chain gene rearrangement in a T-cell lymphoma

Forty-three patients were studied to determine whether light chain gene rearrangements may occur in hematopoietic cells not pertaining to the B-lineage. In only one patient, affected by T-cell lymphoblastic lymphoma, one kappa light chain allele was rearranged. Neither at the protein level nor at the RNA level the rearranged gene was expressed. These data confirm that, although rarely, kappa light chain gene rearrangements may occur in neoplastic T-cells. Furthermore, as in our patient Ig heavy chain genes retained a germline configuration, the present data demonstrate that kappa light chain gene rearrangements may occur regardless of Ig heavy chain gene arrangement.

Immunoglobulin and T-cell receptor gene rearrangements in acute lymphoblastic leukemia--a higher incidence of double rearrangements in patients with myeloid antigen expression

Among 160 patients who were diagnosed as having acute lymphoblastic leukemia (ALL) by French American British (FAB) criteria, 32 patients (20%) expressed myeloid-associated antigens on leukemic blasts (My+ALL). Correlation of immunophenotype with rearrangement of immunoglobulin (Ig) heavy chain and T-cell receptor (TCR) beta chain genes was performed on 73 of these patients (21 were My+ALL). Rearrangements of both Ig and TCR genes (double rearrangements) were detected in 24 patients, including three (19%) of 16 T-lineage ALL. 17 (33%) of 52 B-lineage ALL, and four of five ALL expressing both B and T-cell surface markers. Also a higher incidence of double rearrangements in My+ALL was found as compared with My-ALL (43% vs 29%). This difference was more evident when only B-lineage ALL was considered (50% in My+ patients vs 24% in My- patients). However the difference is not statistically significant yet possibly due to the small number of patients in the study. Further studies on more patients are needed to confirm this. In My-B-lineage ALL, rearrangements of TCR beta chain gene were restricted to certain subgroups (Groups III & IV) of patients who expressed CD10 surface antigens but lacked cytoplasmic Ig. In My+ B-lineage ALL, rearrangements of TCR beta chain gene could be found in various subgroups studied (Groups II through V). Cross-lineage gene rearrangement in My+ALL may involve mechanisms different from those in My-ALL.

Genomic analysis of T-cell receptor and immunoglobulin antigen receptor genes and breakpoint cluster regions in gastrointestinal lymphomas

Sixteen cases of gastrointestinal B- and T-cell lymphoma were investigated for clonal rearrangements of immunoglobulin and T-cell receptor genes. In all cases the immunogenotype data corresponded well with the immunohistochemical findings, thus confirming the biologic heterogeneity of these lymphomas. Some cases could be distinguished by additional heterogeneity in their genotype which could not be detected by immunohistochemical methods. Moreover, the B-cell lymphomas were studied for the presence of the chromosomal translocations t(11;14) and t(14;18) using probes for bcl-1 and bcl-2 genes, respectively. While bcl-1 rearrangement was not present in these gastrointestinal lymphomas, one case of diffuse low-grade lymphoma of mucosa-associated lymphoid tissue and three cases of centroblastic lymphoma (diffuse large cell) could be shown to have detectable bcl-2 rearrangement.