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Protein A-like activity and streptococcal cross-reactions

D Kingston

    Clinical and Experimental Immunology
    |October 1, 1981
    PubMed

    Insights

    Group A streptococci lack protein A-like activity, challenging previous findings of cross-reactions with mammalian tissues. This study clarifies that bacterial cell walls did not cause the observed non-specific antibody absorption in earlier research.

    Area of Science:

    • Immunology
    • Microbiology
    • Biochemistry

    Background:

    • Previous studies suggested antigenic cross-reactivity between group A streptococci and mammalian tissues, potentially due to protein A-like activity.
    • This protein A-like activity was hypothesized to cause non-specific binding of antibodies, confounding experimental results.

    Purpose of the Study:

    • To re-evaluate the presence of protein A-like activity in group A streptococci strains previously implicated in cross-reactivity studies.
    • To determine if this activity was responsible for the non-specific absorption of human IgG observed in earlier research.

    Main Methods:

    • Utilized the mixed reverse passive antiglobulin reaction (MRPAH) assay.
    • Tested strains of group A streptococci and a control strain of Staphylococcus aureus for the absorption of purified human IgG Fc portion.

    Main Results:

    • Group A streptococci strains showed only trace levels of protein A-like activity.
    • The control Staphylococcus aureus strain exhibited strong positive results for protein A-like activity.
    • The previously observed non-specific absorption was not attributable to protein A-like material in the streptococcal strains.

    Conclusions:

    • The protein A-like activity in group A streptococci is minimal and unlikely to be the cause of previously reported antigenic cross-reactions.
    • Earlier findings suggesting cross-reactivity due to this activity require re-evaluation.
    • The study clarifies the role of bacterial components in non-specific antibody binding in immunological assays.

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