| Popis: |
To explore novel aspects of the regulation of MHC class II gene and protein expression I adopted three lines of investigation. 1. Using modern microarray technology to expression profile B cell lines with non-functional CIITA and comparing them to control lines I identified a number of novel candidate genes for CIITA regulation. Of these candidates, the low affinity receptor for IgE (CD23) was shown to be co-regulated with MHC class II in CIITA positive and negative transfectants by both real-time PCR and FACS staining. Evidence from other laboratories points to molecular association between CD23 and MHC class II proteins. The induction of CD23 expression by CIITA further implicates the function of this molecule in MHC class II antigen presentation in B cells. My data confirm suggestions that CIITA has a wider role controlling a group of non-MHC encoded genes that are relevant to MHC class II antigen presentation. 2. In malignant B cells stimulation with Il4 and via CD40 is known to increase their efficiency at inducing CD4+ T cell responses. In primary leukaemia cells and a cell line stimulated in this way an increase in surface CLIP expression and a downregulation of total HLA-DM, but not MHC class II or HLA-DO, was seen. These data establish independent modulation of HLA-DM as a route by which B cells may modulate their peptide repertoire. 3. When immature dendritic cells are stimulated to become mature specialised antigen presenting cells expression of classical MHC class II, and HLA-DM genes is extinguished. I present immunoprecipitation and confocal microscopy date indicating that HLA-DO is expressed in both mature and immature dendritic cells at a low level and by real-time PCR that HLA-DOB shows differential expression from other class II genes. Antigen presenting cells appear to utilise independent modulation of HLA-DM and HLA-DO in order to fine tune the repertoire of peptides they present to T cells. |
