Effects of Radiation on Living Organisms Radiosensitivity of Immune Responses and Mechanisms of Project Title: Immune Reactions 16, Technical Progress in FY 1973: RX-03-O0]-(b) (Conc'd.) of toxoid and specific mouse immunoglobulins (IgG). Test mice were sacrificed for tissues and serum 5, 10, 15, 20, 30, 40, 60 minutes and 2, 3, and 6 hours later. tetanus toxin, Serum antibody levels were determined by neutralization of The free-amino acid (H-3-histidine) level was counted in the sera and the tritium-labeled antitoxin precipitated in slight antigen excess with concentrated tetanus toxoid, The antigen-antibody precipitates were washed three times in cold saline and solubilized with Bio-Solv formula BBS-3 (Beckman) for liquid scintillation counting, The rate of incorporation of H-3-histidine into antibody is being evaluated together with an autoradiographic and histologic study of tne Lymphoid tissues, A series of six experiments with 1,260 mice were carried out concerning the anaphylactogenic properties of complexed antigen. The varioug*‘complexes were prepared in vitro with tetanus toxoid with either isologous mouse anti- toxin, specific mouse IgG, or human tetanus immunoglobulin (H-IgG). Actively immunized mice, normal and irradiated, were challenged 6-8 days post-radiation by i.v. and s,c. injections of the complexes and/or tetanus toxoid only. Challenge with antigen only was far more effective in eliciting severe and facal anaphylaxis than with complexed antigen. When complexes were formed in slight and large antibody excess and injected, fatal anaphylactic shock was not observed. Normally, symptoms of anaphylaxis appear in 5-7 minutes in irradiated mice, When complexes were injected in large antibody excess, the usual symptoms of anaphylactic shock were delayed about 30 minutes, an observation for which there is no explanation. Studies continued in attempts to account for the highly immunogenic properties of complexed antigens as compared with the same dose of antigens injected alone. The enzymes horseradish peroxidase (HRP) and calf mucosa alkaline phosphatase (APH) were used as test antigens. Both HRP and APH in complex with respective specific antibody elicited enhanced primary antibody responses in mice. Several experiments were carried out using HRP and fluid tetanus toxoid (FIT) in complex with specific immunoglobulin subunits. Porter's methods were used to prepare fragments of specific rabbit IgG to form complexes with the various Fab antibody fragments hoping to learn if the whole or only parts of the molecule will elicit an enhanced antibody response when combined with specifie antigen. A new study was started concerning the comparative hematological and immu pressive side effects of chloramphenicol (CAP) and a closely relagie- chemical, chiamphenicol (TAP) in mice. appr have Although TAP is not an © f drug in the United States, more than 15 million people in Europe treated with TAP without the appearance of any known cases of aplastic On the other hand, the rather high incidence of CAP-induced anemia (APA). In preliminary experiments, both CAP and TAP APA has been well-documented, (See Continuation Sheet) 1119212 RX-179