Enhancing effect of protein A on the interaction between opsonized corneocytes and neutrophils in staphylococcal...

Formation of subcorneal pustules characterizes skin lesions infected by Staphylococcus aureus. To elucidate the mechanism underlying the subcorneal pustule formation as well as that of anti-bacterial host defence, we studied the effect of staphylococcal protein A on the interaction between the stratum corneum (SC) and neutrophils. We found that protein A significantly promoted opsonized SC-induced chemiluminescence (CL) in neutrophils. This was specific to SC because no enhancement was observed with opsonized zymosan. It took place even with the serum obtained from a patient with agammaglobulinemia, ruling out the possibility of the involvement of Fc-receptors of neutrophils in this phenomenon. Microscopic observation of such SC revealed an increase in the number of neutrophils adhering to the surface of the protein A-coated corneocytes. Ultrastructural observation showed a distinct deformation of the neutrophils adhering to the surface of the corneocytes, suggesting that they are in an activated state. Such an enhanced interaction between protein A-attached SC and neutrophils seems to play an important role in the host defence mechanism against the invading S. aureus and in the production of the characteristic pustules by the neutrophil-mediated damage of the surrounding epidermal tissue.