Nonidentity of Lyt phenotypes and the radiosensitivity of early and late producers of macrophage migration inhibitory factor in reaction to H-2 complex antigens

MIF production induced at different times after intravenous immunization of mice with irradiated allogeneic splenic cells showed different sensitivity to the treatment with anti-Lyt-antibodies and to gamma-irradiation. The "early" MIF producers induced several hours after alloimmunization were sensitive to irradiation at a dose of 500 rad and to the treatment with anti-Lyt-1- and anti-Lyt-2-antibodies and complement, while the "late" MIF producers which appeared 21 days after alloimmunization were resistant to irradiation at doses of 500 and 1500 rad and to the treatment with anti-Lyt-2-antibodies but sensitive to anti-Lyt-1-antibodies. It is supposed that the "early" MIF producers of the Lyt-1+2+ phenotype are immature precursors of T cells which, in contradistinction to the "late" MIF producers of the Lyt-1+2+ phenotype, are activated and produce MIF without proliferation after a twofold contact with antigen.