Improved detection of virus-specific IgM antibodies. Elimination of non-specific IgM binding.

A non-specific reaction between human IgM and cytoplasmic structures of virus infected cells can often be observed if MgM antibodies to virus antigens are detected by indirect immunofluorescence or by immuno enzyme assays. Formaldehyde selectively inactivates the cytoplasmic receptors for human IgM without affecting the virus structural proteins. Alternatively, receptor-free antigens can be obtained by isolation of nuclei from virus infected cells. Due to reduced background, a more specific and more sensitive detection of IgM antibodies to Epstein-Barr virus, cytomegalovirus or central European encephalitis virus is possible.