RESUMEN
Serial serum samples from patients with acute pancreatitis showed a significant increase in antibodies against methanol-chloroform-extracted lipid antigen from Mycoplasma pneumoniae when tested by complement fixation. The antibodies did not react with antigens prepared from other human mycoplasmas or from pancreatic tissue by lipid extraction. The antibodies were predominantly immunoglobulin M (IgM). No correlation with cold agglutinins or cardiolipid complement-fixing antibodies was found. The IgM antibody response seemed to be prolonged: after 3 to 4 weeks the antibodies were still in many cases exclusively IgM. Similar IgM responses were also found in certain cases of acute meningoencephalitis. We postulate that during the disease antigenic components identical or very similar to major determinants in the M. pneumoniae lipid antigen are revealed and elicit the IgM antibody response. Their resemblance to natural antibodies and their possible biological role is discussed.