Expression of MHC II genes.

Innate and adaptive immunity are connected via antigen processing and presentation (APP), which results in the presentation of antigenic peptides to T cells in the complex with the major histocompatibility (MHC) determinants. MHC class II (MHC II) determinants present antigens to CD4+ T cells, which are the main regulators of the immune response. Their genes are transcribed from compact promoters that form first the MHC II enhanceosome, which contains DNA-bound activators and then the MHC II transcriptosome with the addition of the class II transactivator (CIITA). CIITA is the master regulator of MHC II transcription. It is expressed constitutively in dendritic cells (DC) and mature B cells and is inducible in most other cell types. Three isoforms of CIITA exist, depending on cell type and inducing signals. CIITA is regulated at the levels of transcription and post-translational modifications, which are still not very clear. Inappropriate immune responses are found in several diseases, including cancer and autoimmunity. Since CIITA regulates the expression of MHC II genes, it is involved directly in the regulation of the immune response. The knowledge of CIITA will facilitate the manipulation of the immune response and might contribute to the treatment of these diseases.

Reactivation of hepatitis B but not hepatitis C in patients with malignant lymphoma and immunosuppressive therapy. A prospective study in 305 patients.

BACKGROUNDS/AIMS: The aim of this prospective study was to determine the prevalence of hepatitis B (HBV) and hepatitis C viral (HCV) infection as well as to study the morbidity and mortality of viral reactivations in patients treated with corticosteroid containing chemotherapy. METHODOLOGY: From January 1991 to April 1996, 305 patients admitted for treatment of Hodgkin's disease and non-Hodgkin's lymphoma were tested for HBV, and 181 patients for HCV infection. They were followed-up regularly on a monthly basis with liver biochemistry and viral serology. RESULTS: The prevalence of HBs antigen and hepatitis C antibody was found to be 3.2% and 16% respectively. There were 9 reactivations of HBV among 8 HBs antigen positive patients (78%), one among 35 HBs antigen negative patients (2.8%) and none in HCV positive patients. In 83% of cases, reactivation was connected to chemotherapy and corticosteroids. The overall death rate of HBV reactivation was 37%; in severe hepatitis it was 60%. All fatal reactivations were in anti-HBe positive patients. CONCLUSIONS: The low prevalence of HCV failed to demonstrate an association between hepatitis C viral infection and lymphoma in Slovenia. Reactivation of HBV infection in HBsAg positive malignant lymphoma patients is a common and often fatal complication of treatment.