Beschreibung:
<jats:title>Summary</jats:title><jats:p>A64kDa lipoprotein (LP 64) haemagglutinin (pI 4.9–5.0) was isolated from the membrane of <jats:italic>Mycoplasma gallisepticum.</jats:italic> Triton X‐114 phase partitioning has demonstrated that the hydrophobic nature of this haemagglutinin is due to a lipid portion of the molecule. Autoradiography of [<jats:sup>3</jats:sup>H]‐palmitate‐labelled <jats:italic>M. gallisepticum</jats:italic> revealed the presence of several additional lipoproteins. Immunoelectron microscopy demonstrated the localization of LP 64 to the base of the terminal structure. Densitometric scans of stained polyacrylamide gels of <jats:italic>M. gallisepticum</jats:italic> showed that LP 64 constitutes 1.7% of the total protein. Scans of immunoblots of <jats:italic>M. gallisepticum</jats:italic> indicate that LP 64 is highly immunogenic in chickens, accounting for 7.4% of the total serum IgG response at four weeks post‐infection. A quantitative value for the IgG response to LP 64, relative to the percentage of total protein (the Relative Immunogenicity Index) was 4.4. LP 64 is conserved among several strains of <jats:italic>M. gallisepticum</jats:italic>, but its presence could not be detected in <jats:italic>Mycoplasma synoviae.</jats:italic> Antiserum raised to electroeluted LP 64 reacted specifically with this lipoprotein when assessed on either one‐or two‐dimensional immunoblots of <jats:italic>M. gallisepticum.</jats:italic> This antiserum, as well as Fab fragments, inhibited haemagglutination of chicken erythrocytes and inhibited the attachment of <jats:sup>14</jats:sup>Clabelled <jats:italic>M. gallisepticum</jats:italic> to chicken tracheal epithelium <jats:italic>in vitro</jats:italic> by 62%.</jats:p>