PROTEIN-A OF STAPHYLOCOCCUS-AUREUS IS MITOGENIC FOR IGG-BEARING, BUT ALSO FOR A SUB-POPULATION OF IGM-BEARING AND-OR IGD-BEARING HUMAN-LYMPHOCYTES

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  • 1 January 1980
    • journal article
    • research article
    • Vol. 39  (3) , 417-425
Abstract
The nature of lymphocyte subsets activated by soluble and insoluble protein A (SpA) was investigated by testing the ability of human tonsil populations to form rosettes with human red blood cells coated with SpA (SpA-HRBC) and to respond in vitro to SpA, SpA coupled to Sepharose beads (SpA-Seph) and Staphylococcus aureus strain Cowan I (StaCw). Purified human T [thymus-derived] cells, which were unable to form rosettes with SpA-HRBC, were not activated by SpA-Seph or StaCw, whereas B[bone marrow-derived]-cell enriched suspensions, where the number of lymphocytes forming rosettes with SpA-HRBC was significantly increased in comparison with that found in unfractionated populations, showed DNA synthesis equal to or greater than unseparated lymphocytes. Soluble SpA was unable to activate highly purified B lymphocytes in 3 day cultures and induced higher DNA synthesis in unseparated than in purified human T cells. Tonsil cell suspensions depleted in cells forming rosettes with SpA-HRBC synthesized significantly less DNA in the presence of SpA-Seph and lost the ability to respond to StaCw. Depletion in Ig[immunoglobulin]G-bearing or IgM- and/or IgD-bearing cells induced a reduction in the response of lymphocytes to SpA-Seph and StaCw. Depletion in IgM- and/or IgD-bearing cells induced a more marked decrease in the response to StaCw than depletion in IgG-bearing lymphocytes, while the decrease of the response to SpA-Seph, induced by depletion in IgM- and/or IgD-bearing cells, was lower than that induced by depletion in IgG-bearing lymphocytes. Soluble SpA-induced proliferation was not significantly affected by depletion of cells forming rosettes with SpA-HRBC or of IgG-bear1ng or IgM- and/or IgD-bearing lymphocytes. The mitogenicity of SpA-Seph and StaCw is apparently due to selective binding of insoluble SpA to components present on the membrane of IgG-bearing or IgM- and/or IgD-bearing lymphocytes. The potentiation of T cell response to soluble SpA, induced by the presence in culture of non-T cells, is apparently not due to B lymphocytes which are able to form rosettes with SpA-HRBC and to respond to SpA itself when it is presented to the cells on an insoluble matrix.