Objective of study: Idiopathic thrombocytopenia purpura (ITP) is an autoimmune disorder characterized by the production of antibodies against antigens on the membranes of platelets. ITP is classified into two forms, chronic ITP, typically an adult disease persisting for years and acute ITP, a childhood disorder usually occuring within weeks after a viral infection. A standard therapy for ITP employed in recent years has been the intravenous immunoglobulin G (IVIG) administration. Although there is indirect evidence that certain autoimmune disorders may be due to genetical traits of individuals or families, there is not much direct evidence for the genes' involvement in the development of this type of diseases. In our study we tested whether there is a misfunction of certain cytokine genes which may contribute to the development of this disorder.

Methods: Peripheral blood samples were collected from patients(5 children and 2 adults) with ITP before and after IVIG treatment as well as from healthy individuals. Leukocytes were used for RNA isolation directly or after in vitro culture with or without the mitogens phytohaemagglutinin (PHA) and phorbol 12-myristate 13-acetate (PMA). The expression of the genes was studied by RT-PCR.

Results: Of the cytokines tested so far, IL-la, -1β, -6 and IL-8 mRNAs were constitutively synthesized in all patients before and after treatment, while IL-3 mRNA was absent in all ITP cases studied. Children with ITP, before IVIG treatment showed IL-2 mRNA expression after in vitro stimulation with PHA/PMA in contrast to children with ITP after treatment that expressed IL-2 constitutively. In adult patients IL-2 mRNA synthesis was also constitutive. IL-13 mRNA was not expressed in ex-vivo cells but only after stimulation with PHA/PMA in all cases studied. The fact that, ubnormally, certain cytokine genes were constitutively active in ITP patients, led us to examine the expression of genes involved in apoptosis such as FAS and BCL-2 in order to determine whether this constitutive cytokine expression activates an internal death program to eliminate the autoreactive cell clones. We found that in children with untreated ITP only the BCL-2 gene was expressed while in adults and in children after treatment both BCL-2 and FAS genes were expressed. In conclusion, there is a positive correlation between IL-2 expression and apoptosis in ITP.