Immunochemical Analysis of Mycoplasma Pneumoniae

Summary A lipid fraction extracted from Mycoplasma pneumoniae with chloroform‐methanol contained the major part of the serological activity associated with whole cell preparations in complement fixation (CF) tests with homologous human and rabbit antisera. Like whole cell antigens of M. pneumoniae , the lipid fraction also reacted with bovine sera containing antibody to M. mycoides and with rabbit antiserum against Streptococcus MG. In addition to this major lipid fraction from M. pneumoniae , there was apparently another component which came out in the potassium chloride washings of the lipid extract, in an ethanol soluble, acetone insoluble (Dafaalla B) fraction and in a warm aqueous phenol extract. These fractions all reacted more strongly with rabbit and bovine M. mycoides sera than with homologous rabbit antisera to M. pneumoniae . The cross‐reacting component has not yet been characterised; extracts were of low activity compared with the lipid extract and improved extraction methods are required. In contrast to M. pneumoniae , the chloroform‐methanol soluble fraction of M. mycoides had limited serological activity with homologous rabbit and bovine sera. Its major serological activity appeared in the potassium chloride washings of the lipid extract and in the warm phenol extract made after preliminary chloroform‐methanol extraction of the cells. Like the partly purified galactans previously described, the crude phenol extract reacted with certain human sera with antibody to M. pneumoniae . The heterogenetic reaction of the M. pneumoniae chloroform‐methanol fraction with Streptococcus MG antiserum could not be attributed to contamination of the organisms with medium constituents. The corresponding component in Streptococcus MG has still to be isolated and identified. The relation of the cross‐reaction to the formation of Streptococcus MG agglutinins in patients infected with M. pneumoniae has still to he elucidated.