title: Augmentation and inhibition of delayed hypersensitivity by Staphylococcus aureus protein A.
abstract: The injection of Staphylococcus-aureus protein A into mice, previously exposed to an antigen (sheep red blood cells), is capable of augmenting or inhibiting a primary delayed hypersensitivity (DH) response. SPA enhances DH response to SRBC when given with a greater than optimal sensitizing dose of the antigen. At antigen doses optimal for eliciting DH to SRBC, SPA inhibited DH. A proposed mechanism for the action of Staphylococcus-aureus protein A is based upon the ability of the protein to function as a Fc cellular receptor, thus neutralizing the effect of antigen-antibody immune complexes on DH. The binding of protein A to the Fc portion of antigen-antibody immune complexes effectively prevents subsequent binding of these complexes to Fc cellular receptors, thus eliminating their participation as co-factors in inter-cellular immunological communication. The ability of protein A to both augment and inhibit DH suggests a role for relative concentrations of serum factors and/or cellular receptors in the regulation of a primary DH response.
mesh_terms: D000818:Animals; D000936:Antigen-Antibody Complex; D004912:Erythrocytes / Q000276:immunology; D006968:Hypersensitivity, Delayed / Q000276:immunology*; D051379:Mice; D008811:Mice, Inbred DBA; D011961:Receptors, Fc; D012756:Sheep; D013205:Staphylococcal Protein A / Q000008:administration & dosage / Q000276:immunology / Q000494:pharmacology*
chemical_list: D000936:Antigen-Antibody Complex; D011961:Receptors, Fc; D013205:Staphylococcal Protein A