T lymphocytes from autoimmune thrombocytopenic purpura show a defective activation and proliferation after cytoplasmic membrane and intracytoplasmic mitogenic signals

Comparison of megadose methylprednisolone versus conventional dose prednisolone in hematologic disorders

Glucocorticoids (GCs) are known for their clinically useful effects in immunologic and inflammatory disorders. Although there is a huge volume of knowledge concerning the cellular and molecular effects of GCs, statements regarding their effects in multiple diseases at variable doses are not clear-cut owing to pharmacogenetic differences. The main actions of GCs in hematologic disorders have been related to their differentiation-inducing and apoptosis-inducing effects, but modification of several steps of the hematopoietic and/or immune pathway has also been reported. In our clinic, mega-dose methylprednisolone (MDMP) has been successfully used for treatment of different hematologic diseases, such as leukemias, bone marrow failure in aplastic anemia, hypoplastic anemia, myelodysplastic syndrome, neutropenia, autoimmune diseases, and in some congenital hereditary diseases. Both clinical and experimental studies in our department revealed that MDMP was more effective than conventional dose steroids. It is interesting that MDMP can be curative in some congenital hereditary diseases such as Diamond-Blackfan syndrome. However, more research is required to clarify their roles in biology, physiology, and molecular genetics.

Constitutive impaired TCR/CD3-mediated activation of T cells in IDDM patients co-exist with normal co-stimulation pathways

IDDM is a T cell-mediated autoimmune disease which is paradoxically associated with T cell functional deficiencies. The proliferative response of PBMC under CD3-, Vbeta2-, Vbeta8- and Vbeta7-stimulation was investigated in IDDM and NIDDM patients, non-diabetic first-degree relatives and control subjects. Despite normal surface expression of the TCR/CD3 complex, the TCR/CD3-mediated proliferation of PBMC from IDDM patients was significantly impaired compared to control subjects (P<0.05). This defect was specific for the autoimmune disease, constitutive and not linked to the class II MHC genotype, to metabolic disturbances or to presence of specific autoantibodies. Inefficient activation of T cells was not related to a lower capacity of CD28 to transduce co-stimulative signals because proliferative responses under CD2/CD28 stimulations were similar in IDDM and control groups. The IL-2/IL-2 receptor system was functional because unstimulated PBMC proliferated in response to increasing amounts of IL-2. Nevertheless, despite normal expression of CD25, addition of IL-2 did not normalize the proliferative defect linked to IDDM. In conclusion, excluding a faulty co-stimulation pathway, these results are in favour of a constitutive defect in the CD3/TCR transduction machinery, increasing sensitivity to apoptosis or anergy in T cells from IDDM patients.

Analysis of transmembrane signalling and T cell defects associated with idiopathic thrombocytopenic purpura (ITP)

Adult chronic idiopathic thrombocytopenic purpura (ITP) is an autoimmune disease characterized by production of autoreactive antibodies to platelet antigens. It is now becoming clear that autoantibody production, in general, is regulated by T helper (Th) cells. Several recent studies have examined potential defects in T cell function in this disease and have demonstrated that patients with ITP possess abnormal lymphocyte activation and Th1/Th2-mediated cytokine production. Although the underlying cause(s) of aberrant T cell function in this disease are not known, studies from other models of autoimmune disease indicate that defects in T cell transmembrane signalling can be causally linked to abnormal T cell activation and cytokine production. This review will present some of the major T cell signalling pathways and discuss how altered T cell signalling may be linked to autoimmunity with an emphasis on ITP. Recent preliminary findings of a potential defect in the signal transduction apparatus in lymphocytes from three patients with ITP will also be presented.

Role of the T cell receptor in idiopathic thrombocytopenic purpura (ITP)

During the past few decades a number of studies has described T cell defects and attempted to elucidate their role in the pathogenesis of idiopathic thrombocytopenic purpura (ITP). Some studies implicate T cells as potential initiators of autoantibody production in ITP. However, only a few of these have studied the role that the T cell receptor may play in the pathogenesis of ITP. In a variety of autoimmune syndromes interest has focused on the alpha- and beta-chains of the T cell receptor. Deviations from the normal T cell receptor gene usage have been reported in rheumatoid arthritis, systemic lupus erythaematosus and multiple sclerosis. Usually, these studies have shown a restricted heterogeneity of T cell receptor variable gene usage. The studies on the T cell receptor in ITP have included a limited number of patients, which makes it difficult to evaluate the significance of the role that the T cell receptor may play in the pathogenesis of ITP. Further studies are warranted.

Abnormal gamma IFN and alpha TNF secretion in purified CD2+ cells from autoimmune thrombocytopenic purpura (ATP) patients: their implication in the clinical course of the disease

Gamma inferferon (gamma IFN), alpha tumor necrosis factor (alpha TNF), and interleukin 6 (IL-60) are cytokines produced by a wide variety of cells, including T lymphocytes and NK cells. These cytokines affect B-cell proliferation and differentiation into immunoglobulin secreting cells. In addition, gamma IFN and alpha TNF also enhance the function of macrophages, upregulating the expression of their IgG receptors. Abnormalities in the production of these cytokines may be involved in the clinical course of autoimmune thrombocytopenic purpura (ATP). This paper describes the production of these cytokines in PHA-stimulated peripheral blood CD2+ cells from ATP patients. Both gamma IFN and alpha TNF were significantly increased in PHA-stimulated CD2+ cells from therapy-dependent ATP patients (platelet counts < 50,000/microliter), as compared to ATP patients with stable disease (sustained platelet counts < 50,000/microliter without need treatment) (P < 0.05). No significant differences were found in gamma IFN production by PHA-stimulated CD2+ cells between therapy-dependent ATP patients and healthy controls (P < 0.05). However, the production of alpha TNF by PHA-stimulated CD2+ cells from therapy-dependent ATP patients was significantly higher compared to that found in healthy controls (P < 0.05). There were no significant differences in IL-6 production by PHA-stimulated CD2+ cells from ATP patients and healthy controls (P < 0.05). These findings demonstrate abnormal gamma IFN and alpha TNF secretion in purified CD2 cells from ATP patients. The clinical severity of the disease is associated with the altered secretion of these lymphokines by CD2 cells.

Persistent lymphocytosis of natural killer cells in autoimmune thrombocytopenic purpura (ATP) patients after splenectomy

We report three patients with primary autoimmune thrombocytopenic purpura (ATP) who developed an absolute lymphocytosis (lymphocyte count > 5 x 10(9)/l) after splenectomy and with a lymphocyte count between 5.4 and 8.9 x 10(9)/l. An immunophenotype study showed that the peripheral blood lymphocytosis was a persistent NK cell expansion (CD2+, CD56+, CD3-), and was characterized by a typical large granular lymphocytes (LGL) morphology. Two of these three ATP patients were refractory to splenectomy.