Mechanisms of genetic control of immune responses

The mechanisms underlying Ir gene control of CMI were addressed by examining the DTH and Tprlf responses specific for the synthetic polymers GT, GAT, and GA. We show that BALB/c mice (GAT/GA responders, GT nonresponders) primed with GT fail to develop DTH and Tprlf responses specific for GT, GAT, or GA. GAT immunization resulted in DTH responses that could be elicited not only with GAT and GA but also with GT, demonstrating that GT-specific T_DH are present in nonresponder mice. GT-specific DTH was transferred with Thy-1⁺ Lyt-1⁺2^–, H-2 Irestricted, nylon wool nonadherent cells. GA-primed BALB/c mice developed GAT- and GA-, but not GT-apecific DTH responses, indicating that GA and GT do not cross-react at the T-cell level. The ability of GAT [but not a mixture of GA plus GT, or GT electrostatically complexed to the immunogenic carrier MBSA (GT-MBSA)] to induce GT-specific DTH suggested a requirement for covalent linkage of stimulatory GA and nonstimulatory GT determinants present on the GAT molecule. Similarly, GT-specific in vitro Tprlf responses could be demonstrated in GAT-primed mice exhibiting significant levels of GT-specific DTH but not in GT- or GT-MBSA-primed mice. Tolerization experiments also suggested that GT-specific Th were involved in the development of GT-specific DTH in GAT-primed mice. The GT nonresponsiveness of BALB/c mice for DTH and Tprlf responses could not be reversed by treatments designed to abrogate Ts activity (priming with GT-MBSA and CY injection), nor could GT-primed cells be shown to inhibit the development or elicitation of GT-specific CMI in GAT-primed mice during the afferent and/or efferent stages of DTH. Our results suggest that GT nonresponsiveness does not result from the absence of GT-specific T cells or preferential induction of Ts. The results are discussed in the context of hole-in-the-repertoire and antigen presentation (determinant selection) models of Ir gene control.Abbreviations used in this paper APC antigen-presenting cells - BSA bovine serum albumin - BSS Mishell-Dutton balanced salt solution - CFA complete Freund's adjuvant - CMI cell-mediated immunity - CY cyclophosphamide - DTH delayed-type hypersensitivity - GA poly(Glu⁶⁰Ala⁴⁰) - GAT poly (Glu⁶⁰Ala³⁰Tyr¹⁰) - GT poly(Glu⁵⁰Tyr⁵⁰) - GT-MBSA GT complexed to methylated bovine serum albumin - It immune response - LN lymph node - PPD purified protein derivative of tuberculin - TDH DTH T cells - Th helper T cells - Tprlf T-cell proliferation - Ts suppressor T cells - TsF T-cell suppressor factor(s)     

Detection of Sendai virus fusion with human erythrocytes by fluorescence photobleaching recovery

The subunit stoichiometry of the ATP synthetase (CF₁-CF₀) immunoprecipitated from Triton X-100 extracts of chloroplast thylakoid membranes was determined to be α₃, β₃, γ, δ, ? (CF₁) and I_0.3, II_0.6–0.9, III₄₍₆₎ (CF₀). Antibodies against the polypeptides α, β, γ, δ, I, II and ? combined specifically with the isolated subunits as analysed by the protein blotting method. Applying this technique, antibodies against the CF₁ subunits were found to form complexes with the corresponding polypeptides of thylakoids, whereas those against I (M_r 20 000) and II (M_r 17 000) combined with M_r 26 000 and M_r 24 500 membrane polypeptides, respectively. The M_r 26 000 polypeptide was identified as the major subunits of the light-harvesting chlorophyll a/b-protein (LHCP) complex and the M_r 24 500 component seems to be functionally connected with this complex. From the results it is concluded that the chloroplast ATP synthetase consists of the subunit of the α, β, γ, δ, ? and III (proteolipid only and that proteolytically altered LHCP polypeptides bind artifically to the protein complex during isolation.     

New Class of Streptomycin-Resistant Mutants Incompatible with supX Suppressor Mutations in Salmonella typhimurium

Streptomycin-resistant colonies of Salmonella typhimurium appearing in platings of supX suppressors of strain leu-500 are less variegated in size than are those derived from strain leu-500 counterparts. Several of the streptomycin-resistant leu-500 clones, furthermore, yield suppressors and revertants of the leu-500 auxotrophy at unusually low rates, suggesting that they provide a genetic background inimicable to supX suppression. Two such "suppression-restrictive" leu-500 streptomycin-resistant (str) mutants, designated strains M(1) and M(4), were characterized as to their ability to receive the trp-supX-cysB linkage region by transduction. Coentry of a donor supX deletion mutation with the selected trp(+) marker was not observed even though these sites display more than 10% linkage in control experiments. This was demonstrably the result of nonviability of the combined supX mutant, M(1) or M(4) streptomycin-resistant genotype, rather than the lack of suppression of the leu-500 imparted auxotrophy. Both M(1)- and M(4)-type resistance was accompanied by pleiotropic effects resembling those caused by strB (nonribosomal)- rather than strA (ribosomal)-type resistance, but both restrictive mutants had a high upper limit of resistance corresponding to that of strA-type mutants. Transduction analyses indicated that the str character of neither the M(1) nor the M(4) strain was linked to the strA or the strB gene. These mutations define a previously undescribed locus, which we propose to designate strC, apparently related to streptomycin uptake rather than its intracellular action. Mutation at this locus is evidently incompatible with the inactivation or removal of the supX site, suggesting a functional association between products of the genes.     

Effect of estradiol on splenic repopulation by endogenous and exogenous hemopoietic cells in irradiated mice

Estradiol treatment of irradiated mice during repopulation of their spleens by endogenous hemopoietic cells reduced the number of myelocytic colonies and increased the numbers of erythropoietic and undifferentiated colonies. The inhibitory effects of the hormone on myelopoiesis were not dependent on stimulation of erythropoiesis, since they occurred in the absence of erythropoiesis in mice made polycythemic by hypertransfusion. Treatment of bone marrow donors with estradiol reduced the ability of their marrow cells to form spleen colonies, particularly reducing the proportion of myelopoietic colonies relative to the total number of colonies of all types. Conversely erythropoietic colonies, though reduced in absolute number, were increased in relative number. Such treatment also decreased the volume and cell content of the marrow cavity through stimulation of endosteal bone formation. Estradiol treatment of lethally irradiated recipient mice did not detectably alter the total numbers or types of hemopoietic spleen colonies formed in these animals from transplanted marrow cells; however, without estradiol treatment, myelopoietic colonies were so few and erythropoietic colonies so numerous that the effects of the hormones may have been undetectable by the methods employed. The sex of the donor or recipient mouse did not affect the numbers or types of colonies formed, suggesting that endogenous levels of estradiol were too low to exert effects dectectable by the methods used. However, since our mice were only 8 weeks old, the data do not exclude the possibility that older female mice, with higher levels of estradiol, would have differed from males in relative numbers of myelopoietic as compared with erythropoietic colonies.