Inhibition of pathogenic effect of effector T cells by specific suppressor T cells during influenza virus infection in mice

Abstract

Mice infected with an aerosol of influenza type A virus, or immunized with purified UV-inactivated whole virus or with viral subunits, develop a transient delayed-type hypersensitivity (DTH) which peaks 5–7 days after immunization¹. The intensity of DTH is greatly enhanced and sustained when mice are pretreated with cyclophosphamide¹. The reaction is maximal 24 h after elicitation, has classical tuberculin-type histology and is transferable by immune H–2I region restricted Lyt-1⁺2⁻ T cells (T_d) but not by immune serum^1,2. These T_d cells not only fail to protect mice against influenza virus infection³, but increase the mortality rate due to influenzal pneumonia following challenge with homologous lethal virus^3,4. On the other hand, antigen-specific suppressor T (T_s) cells which inhibit DTH are readily generated during influenza virus infection, and are detectable for at least 40 days thereafter⁵. The ease with which they are induced and maintained during the infection may be of evolutionary advantage⁶. In support of this, we now report that these T_s cells can reverse the pathogenic effect of T_d cells thereby demonstrating a beneficial influence of T_s, cells in a viral disease.