Molecular Method Directly Identifies Antigens

A novel method for identifying antigens is based on the isolation of T cells present in samples of affected tissues obtained from patients with autoimmune diseases.

The genetic blueprints for the specific antigen-binding T-cell receptors (TCRs) produced by these cells, have been transferred into a cultured cell line that grows well in the laboratory and contains a version of the gene for the Green Fluorescent Protein (GFP) that is specifically expressed if a TCR is activated.

Scientists at the Ludwig Maximilians University (Munich, Germany) collaborated with a team from the Max Planck Institute for Neurobiology (Munich, Germany) to develop the new method that can identify the antigens that initiate immune reactions and may help to prevent misdirected attacks in the future. They used genetic engineering techniques, to generate cells that emit green fluorescent light when stimulated by the binding of a cognate antigen.

The T-cells are incubated with a collection of some 100 million peptides, which are short amino acid sequences like those normally recognized by TCRs. If even a single peptide represented in the library is recognized by a specific TCR, the corresponding cell synthesizes GFP and it can be detected by its green fluorescence, allowing the bound antigen to be identified. The method thus provides a relatively simple way of identifying single autoimmune antigens from huge numbers of possible suspects.

An initial test carried out using cells specific for a known influenza antigen confirmed the efficacy of the method. The investigators were able unequivocally to select out and identify the correct antigen from all the other peptides used in the test. The technique is so rapid and so sensitive that several million antigens can be analyzed in a matter of hours. This opens up a wide range of possible applications, ranging from the analysis of the reactive antigens responsible for autoimmune diseases like multiple sclerosis or psoriasis to the identification of new tumor or viral antigens. The practical potential is so significant that the method is the subject of a patent application. The study was published online on April 8, 2012, in the journal Nature Medicine.

Related Links:
Ludwig Maximilians University
Max Planck Institute for Neurobiology