Investigation of the mechanisms by which “enhancing” antiserum prevents induction of delayed hypersensitivity to protein antigens in mice

Abstract

Enhancing antibody (referred to here as “contrasensitizer”), produced in hyperimmunized mice and injected daily into normal mice during the first 5 days of their exposure to purified protein antigens in incomplete Freund adjuvant, prevents these mice from developing delayed (tuberculin-type) hypersensitivity by specifically blocking antigen-host cell interactions in the earliest stages of sensitization. An antigen inoculum is permanently inactivated by such a series of contrasensitizer injections; but treated mice are not made immunologically unresponsive, for they can respond normally to a second inoculation not neutralized by a second course of contrasensitizer injections. The inhibitory antibody, apparently a 7S gamma-1 globulin and not a precipitin, cannot prevent activation of an anamnestic response; but its administration can be delayed as much as 4 days after original antigen inoculation and still prevent primary induction of delayed hypersensitivity. Much less effectively, it also suppresses induction of Arthus hypersensitivity. In terms of retained inhibitory activity, it is estimated to have a half-life of only 10 to 12 hours.