Search

CD4 and CD8 T-cell clones were generated using the Mx9 monoclonal antibody (mAb), which recognizes the Vβ8 T-cell receptor (TcR) gene family. The interaction of these clones with the Mx9 antibody was analysed and all were found to be specifically stimulated to proliferate by plastic- adherent Mx9. In the presence of Mx9 or its F(ab')2 fragment, CD8+Mx9+ clones were capable of specifically lysing the CD4 + Mx9-T-cell clones. No lysis was seen of Mx9+ T-cells, or in the absence of the antibody. Conversely CD4 Mx9+ cells did not have lytic function. These results indicate that cross-linking of T cells via their antigen-specific receptors may initiate a unidirectional killing. Unlike previously reported lytic systems involving anti-TcR antibodies (e.g. anti-CD3), these results suggest that this mechanism may have an important physiological role in immune regulation. Antis idiotypic antibodies have been shown to recognize T-cell receptors. These may exert profound immunosuppressive effects by inducing the lysis of the helper cells or B cells. [ABSTRACT FROM AUTHOR]

The expression of Ia-like antigen (Ia) has been studied in 55 cases of acute myeloid leukaemia (AML) in correlation with the expression of both Sudan Black (SB) and naphthol AS-D chloroacetate esterase (NCAE) stains. Operationally the AML cases were divided into three groups using only NCAE expression on the leukaemic cells: the first group with early maturation stage (MS1) consisted of 30 cases with less than 10% NCAE positive cells (SB: 15-100%): the MS2 group of 14 cases with 10-70% NCAE positive cells (SB: 65-100%) and the MS3 group of 11 cases with 70-100% NCAE positive cells (SB: 89-100%). Ia expression was determined by complement-dependent cytotoxicity, immunofluorescence and immunoperoxidase methods. A similar high percentage (80%) of patients from both group MS1 and MS2 expressed Ia on the surface of 32-100% of the cells. Furthermore, individual comparison of all cases from these two groups showed no correlation between Ia, NCAE and SB expression. Only in the 11 cases from the MS3 group, which included nine cases of promyelocytic leukaemias, was there a correlation between very low expression of Ia antigen with the high NCAE expression. Thus, for AML with a low degree of differentiation the expression of Ia seems to be independent of conventional cytochemical markers of cell maturation.

Ectoenzyme activities were determined in peripheral blood cells from patients with acute leukemias, from normal controls, and in cells of hematopoietic cell lines. In common acute lymphoblastic leukemia, cell membrane-associated 5'-nucleotidase (5'-N) activity was significantly higher than in acute T and unclassified lymphoblastic leukemias. In acute myeloblastic and myelomonocytic leukemias, cells contained significantly higher gamma-glutamyl transpeptidase (gamma-GT) activity than in lymphoblastic leukemias. Normal B lymphocytes differed from T cells and monocytes mainly in their 5'-N activity, whereas in monocytes, gamma-GT activity was more pronounced than in other normal blood cells. Hematopoietic cell lines showed some distinct patterns of ectoenzyme activity. Most B cell lines had high 5'-N and (Na-K-Mg) adenosine triphosphatase activities. In lines of myeloid origin, elevated gamma-GT values were found. In lymphoid stem cells and in T lymphoblast lines, most ectoenzyme activities were lower than in the other cell lines. In some cell lines, characteristic high-activity marker enzymes were detected.