Isolation, ultrastructure and antigenicity ofMycoplasma gallisepticummembranes

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Abstract
Summary: The cell membrane ofMycoplasma gallisepticumwas isolated by lysing the cells with digitonin. Chemical and density-gradient analyses and electron microscopy showed the isolated membranes to be relatively free of cytoplasmic contaminants. The density of the membranes exceeded that of other mycoplasma membranes, indicating a higher protein content. Small vesicular extensions seen in the sectioned membranes were interpreted as empty blebs.The isolated membranes, but not the cytoplasmic fraction, elicited in chickens the production of growth-inhibiting, agglutinating and haemagglutination-inhibition antibodies toM. gallisepticumin titres resembling those obtained by injection of whole cells. The peak of the serological response varied with the serological test employed. The rapid slide-agglutination test became positive as early as 3 days after the first injection of only 50 μg. of membrane protein. The haemagglutination-inhibition antibody titre reached its peak at about 10 days after the first injection, while that of the growth-inhibiting antibodies was reached only at about 25 days. The addition of adjuvant to the membrane antigen did not improve the production of the growth-inhibiting antibodies in chickens, but it produced some improvement in rabbits. Our results support the thesis that the chief immunogens ofM. gallisepticumreside in the cell membrane of this organism.