SUMMARY: The immunological basis for resistance of certain strains of to the bactericidal action of normal human serum was studied by investigating the potential role of factors which are known to interfere with each of the sequential steps that result in immune lysis of Gram-negative bacteria. Strains of were characterized as serum-sensitive (ser) or serum-resistant (ser) on the basis of their sensitivity to lysis by the sera of six normal individuals. Neither intrinsic resistance to the lytic action of activated human complement nor inaccessibility of the cell membrane to C5b accounted for serr. Outer membrane lipopolysaccharide (LPS) was the target antigen for lytic antibody in normal human sera. The gross chemical composition and molecular size of the LPS of the strains were heterogeneous and no consistent patterns of differences between those extracted from ser and from ser strains were found. Neither IgA nor IgG ‘blocking’ antibody in normal human serum was responsible for ser. We conclude that ser results from the absence from the LPS of the strains of antigenic loci for the lytic antibody in most normal human sera, or, expressed as a function of the host, the absence from the sera of most normal humans of lytic antibody directed against LPS antigenic loci for immune lysis.


Article metrics loading...

Loading full text...

Full text loading...


Most cited this month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error