This web page was produced as an assignment for an undergraduate course at Davidson College.
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Humoral Immunity of MRSA
Humoral immunity is the "antibody-mediated specific immunity made in a humoral immune response. Humoral immunity can be transferred to unimmunized recipients by using immune serum containing specific antibody" ( Immunobiology, 6/e; Garland Science, 2005). The extracellular spaces of the human body, where many infectious bacteria multiply, are protected by the humoral immune response. In this response, antibodies are produced by B cells and they cause destruction of extracellular microorganims and stop the spread of infection intracellularly. These antibodies secreted by B cells bind to antigens on the cell surfaces of invading pathogens, which in turn flags the for destruction by killer cells.
Protein A is a cell wall surface protein found on S. aureus bacteria. This protein binds to the FC fragment of antibody molecules between the second and third constant regions of the heavy-chain polypeptides This is a response of the bacterium to the destructive potential of the Fc portion because the addition of protein A prevents the Fc region from working. In serum, the S. aureus bacteria will bind IgG molecules in the wrong orientation on their surface which disrupts opsonization and phagocytosis.
The morbidity of MRSA infection may be dependent upon the status of host immunity, especially humoral immunity, which is believed to play a significant role against staphylococcal infection ( http://jac.oxfordjournals.org/cgi/content/full/44/6/767), thus showing the importance of the humoral immune response in fighting off infection by MRSA.
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