Clinical significance of HLA-DR+, CD19+, CD10+ immature B-cell phenotype and CD34+ cell detection in bone marrow lymphocytes from children affected with immune thrombocytopenic purpura.

In children with immune thrombocytopenic purpura (ITP), bone marrow lymphocytes can express the common acute lymphoblastic leukemia antigen (CALLA) pattern with no evidence of leukemia or lymphoma. Bone marrow lymphocytes from 23 children and 20 adults affected with ITP were studied to determine the incidence and the clinical impact of lymphocytes with the immature B-cell phenotype and CD34+ cell expression. In this investigation we identified a group consisting of 52% of the children who showed the immature B phenotype, while the remaining 48%, similarly to adult ITP displayed an increase of T-cell antigens. CD34 was positive in 53% of children, but it was present in only half of the patients with the immature B phenotype and it was always absent in adults. IgH genes disclosed a germline configuration in all six patients in the immature B phenotype group. No difference was found in the two groups of children in terms of age, presentation of the disease or final outcome. Finally, no patient in either children's group has developed an acute lymphoproliferative disorder.

Thrombotic thrombocytopenic purpura: a rare late complication of allogeneic bone marrow transplantation.

Thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS) usually occurs in a setting of systemic infection or graft-versus-host reaction during the first weeks following transplant. We report a case of fatal TTP that developed eight months after allogeneic bone marrow transplantation (BMT) without any evident association with other transplantation-related complications. Conditioning chemotherapy could have induced the disorder by causing damage to the vascular endothelium. The removal of immunosuppression, including cessation of cyclosporin A (CyA), may have precipitated the disease.

Independent modulation of von Willebrand factor and fibrinogen binding to the platelet membrane glycoprotein IIb/IIIa complex as demonstrated by monoclonal antibody.

In this study we have used two new monoclonal antibodies, designated LJP5 and LJP9, as well as a previously described one, AP2, all specific for the platelet membrane glycoprotein (GP)IIb/IIIa complex. None of them reacted with dissociated GPIIb or GPIIIa. The monovalent Fab fragment of both LJP5 and LJP9 bound to unstimulated platelets in a saturable manner, but binding was markedly decreased after platelets had been incubated at 37 degrees C in the absence of added extracellular calcium. The binding of LJP9 was not affected by AP2, but was blocked by excess LJP5. On the contrary, the binding of LJP5 was blocked in the presence of both AP2 and LJP9. Thus, these antibodies bound to distinct epitopes of GPIIb/IIIa. At saturation, the binding to unstimulated platelets was between 2.41 and 10.9 X 10(4) molecules/platelet for LJP5 and between 3.47 and 9.1 X 10(4) molecules/platelet for LJP9 (range of 11 and 10 experiments, respectively). Binding increased up to 50% after thrombin stimulation. The estimated association constant, Ka, was 2.7 X 10(7) M-1 for LJP5 and 3.85 X 10(7) M-1 for LJP9. Both LJP5 and LJP9 partially inhibited the association of 45Ca2+ with the surface of unstimulated platelets. Moreover, both antibodies blocked the binding of von Willebrand factor (vWF) to stimulated platelets, whereas only LJP9, but not LJP5, blocked fibrinogen binding. LJP9 was also a potent inhibitor of platelet aggregation, whereas LJP5 was without effect in this regard. The results of the present study demonstrate that independent modulation of vWF and fibrinogen binding to stimulated platelets can be attained with monoclonal antibodies directed against distinct epitopes of GPIIb/IIIa.

Functions of T cells and recruitment of cellular response after in vitro mitogenic stimulation of lymphocytes in chronic lymphocytic leukaemia.

In vitro stimulation of peripheral blood lymphocytes from ten patients with chronic lymphocytic leukaemia (CLL) was investigated under various culture conditions. It was confirmed that the mitogenic reactivity of whole cell populations (PBL) was delayed and depressed. When CLL rosette-forming cells (RFC) were stimulated, their 3H-thymidine uptake was increased, but the pattern of the response was similar to that of whole PBL, thus suggesting some impairment of these cells. Furthermore, in order to evaluate the possible recruitment of B cells, generally thought to be unresponsive, some co-culture experiments were performed in which 10(4) normal lymphocytes and 10(5) CLL whole PBL or RFC-depleted cell populations were stimulated with mitogens. An amplified response of the CLL lymphocytes was obtained in all co-cultures, and this effect was more evident when specific T cell stimulants were used; autologous CLL T lymphocytes, on the contrary, failed to display such a 'synergic' effect. These results indicate that normal lymphocytes are able to recruit a large number of CLL lymphocytes in the mitogenic response; furthermore, the fact that in co-cultures of CLL T-depleted fractions a better response was obtained with T cell mitogens suggests that the definition of CLL as a clonal expansion of unresponsive 'B' lymphocytes may be inadequate.