Delayed hypersensitivity to Staphylococcus aureus.

To the Editor.— Staphylococcal vaccines, autogenous and stock, have been widely used for many decades with results that have been, on the whole, disappointing. On the contrary, appropriate use of staphylococcal antigens in the hands of certain clinicians has been notably successful in many staphylococcal infections and in upper respiratory illnesses in which staphylococci are opportunistic invaders. The explanation of this puzzling conflict of observations has been given in part. 1 Antibacterial antibodies are simply not effective against Staphylococcus aureus in the sense that they are against pneumococci and Streptococcus pyogenes . This surprising fact is in consequence of the unique immunochemical properties of the surface of the staphylococcal cell. On the positive side we are learning, however, that delayed-type hypersensitivity to S aureus which is all but ubiquitous, affords a practical basis for evoking resistance not only against S aureus , but also against a variety of intracellular infectious agents, both