The recognition specificity of a murine helper T cell for hemagglutinin of influenza virus A/PR/8/34.

A T cell line was established in long-term tissue culture from spleen cells of BALB/c mice immunized with influenza virus PR8 (A/PR/8/34(H1N1)) by continuous restimulation with PR8 virus and syngeneic x-irradiated spleen cells. This T cell line and clones derived from it have now been propagated for over 1 yr "in vitro". The T cell line and the clones, upon stimulation with Con A in the absence of antigen and irradiated spleen cells, as upon stimulation in the presence of antigen and adherent cells, produce T cell growth factors, B cell replication and maturation factors, and colony-stimulating factors, as tested by restimulation of proliferation of a clone of cytolytic murine T cells, of lipopolysaccharide-activated B cell blasts, and by macrophage/granulocyte colony formation of murine bone marrow cells, respectively. The T cell line and the clones help syngeneic B cells in the presence of syngeneic irradiated spleen cells and PR8 virus to proliferate and mature into clones of cells secreting virus-specific antibodies. In the presence of PR8 virus and of a bystander antigen, such as sheep red cells, B cells specific for this bystander antigen are also induced. Adoptive transfer of the T cells i.v. into syngeneic nu/nu BALB/c mice enable the recipient mice to produce, upon challenge with PR8, virus-specific antibodies and to clear virus infection of the lung. The virus-specific T cell line and the clones are restricted by H-2 antigens of the d-haplotype, probably by Iad, and recognize a determinant on the hemagglutinin (HA) molecule of PR8 virus. Fifty to 100 fmol of virus-associated or free HA suffice for stimulation as measured by proliferation assays. The stimulating determinant is present on the HA of all natural virus isolates of the H1 subtype, is absent from virus isolates of the H2 and H3 subtypes, and is abolished if glutamic acid at position 115 of the HA1 polypeptide of PR8 is replaced by lysine.