26 research outputs found
In Vitro Induction of Specific T Cells Able to Help in the Generation of Delayed-Type Hypersensitivity by Thymus-Dependent and Type-II 'Thymus-Independent' Antigens
Hypothesis: Immunological Help is Reciprocally Delivered between Different Subpopulations of Lymphocytes
Immunological Tolerance to the Thymus-Independent Antigen Dextran can be Abrogated by Thymus-Dependent Dextran Conjugates: Evidence against Clonal Deletion as the Mechanism of Tolerance Induction
An in vivo comparison of bacillus CalmetteâGuĂ©rin (BCG) and cytokine-secreting BCG vaccines
A recombinant bacillus CalmetteâGuĂ©rin (BCG) vaccine has been developed, which constitutively secretes interleukin (IL)-2. Groups of deer were immunized with either normal BCG (Pasteur 1173 P2 strain) or recombinant BCG (rBCG/IL-2) and their immune responses were monitored over 3 months. Animals gained weight over this period and showed no signs of adverse reactions to either vaccine. Lymphocyte transformation responses did not differ significantly between the two groups. No antibody that was specific for BCG was detected in any animal. Intradermal skin-test responses to BCG antigens showed that the rBCG/IL-2 induced a smaller delayed-type hypersensitivity response than the normal BCG. Cytokine transcription was determined by reverse transcriptionâpolymerase chain reaction (RTâPCR). While IL-2 and interferon-Îł (IFN-Îł) levels did not differ significantly between the two groups, the level of IL-4 was found to be lower in the group given rBCG/IL-2. This resulted in a strong interferon-Îł:IL-4 ratio, suggesting a skewing of the immune response towards a Type 1 response. The rate at which the vaccine was eliminated from the host was the same regardless of whether BCG or rBCG was used. At autopsy (3 months after vaccination) 99·99% of the organisms had been eliminated. The small number of organisms isolated from the draining lymph node of animals given rBCG/IL-2 were grown in antibiotic-containing media. They were shown to still contain the shuttle plasmid and to secrete biologically active IL-2, indicating that the plasmid was stably maintained despite the host's immune response and in the absence of antibiotic selection