Gene expression analysis in sarcoidosis

Sarcoidosis is a systemic granulomatous inflammatory disease for which no single cause is known. There are reports about a trigger mechanism by different bacteria and viruses, such as Mycobacteria, but their role in this disease is still unclear. The disease is characterized by an immune reaction of delayed type (type IV). A genetic basis for the disease has been looked for in all previous investigations, but just focusing on single genes, such as major histocompatibility molecules, or inflammatory mediators, like interleukins and cytokines. Sarcoidosis like other immune or autoimmune diseases, however, most probably is not caused by a single gene, but by a deregulated network of genes. In a pilot study we have investigated bronchoalveolar lavage cells from sarcoidosis patients, stimulated by dead M. avium by gene expression profiling. By comparing these results with similarly handled lavage cells from tuberculosis (TB) and extrinsic allergic alveolitis (EAA) patients we have found four genes exclusively upregulated in sarcoidosis, namely B-myb, FABP4 and two ESTs. Besides these many other genes were upregulated in sarcoidosis, but also TB and EAA, such as c-akt, Tcl-1, Trail-receptor, and thymosin- alpha. From these preliminary results we speculate that in sarcoidosis there might be an constant upregulation of genes, causing a prolonged proliferation of lymphocytes (B-myb), and a preselection of T-lymphocytes (c-akt, Tcl- 1). In addition the apoptotic pathway is downregulated. We will try to establish the knowledge of the time sequence of up- and downregulated genes, classifying them as early, intermediate, and late response genes. We will generate a gene library for sarcoidosis, quantify and define the origin of those genes responsible for the immune reaction with respect to subsets of lymphocytes (helper and suppressor) and macrophages, and demonstrate the protein translation in the respective cell populations. To elucidate the role of Mycobacteria, gene expression from stimulated cells will be compared with unstimulated cells. In addition we will compare gene expression of sarcoidosis patients from different ethnic populations. Finally we will clarify the interaction of relevant genes by means of small interfering RNA.