Therapeutic immunology最新文献

The rejection of a vascularized xenograft between phylogenetically distant species is a result of natural antibody binding to the graft endothelium and the activation of complement. The subsequent dysfunction of endothelial cell physiology results in the loss of vascular integrity and ultimately the failure of the graft. Strategies aimed at preventing the initial steps of antibody binding and complement activation have successfully prevented hyperacute rejection in experimental models resulting in a significant prolongation of xenograft survival. The rapidly increasing understanding of the mechanisms of xenograft rejection, and the potential ability to counter these mechanisms using recent advances in molecular biology, immunology, and vascular biology, provide encouragement that discordant xenotransplantation may prove clinically applicable.

Recent reports demonstrating that the lethal effects of radiation on tumour cells can be augmented by tumour necrosis factor-alpha (TNF-alpha) prompted us to investigate whether this premise holds true for the LS174T human colon adenocarcinoma cell line. Three different techniques were used to assess cell damage: 3H-thymidine (3H-TdR) uptake, clonogenic survival, and vital dye exclusion. In these assays human recombinant TNF-alpha treatment was administered before single-dose-gamma-radiation at 4, 6, 8, or 10 Gy. Oxygen radical formation by the tumour cells in the presence of TNF-alpha and radiation, alone and in combination, was also investigated. TNF-alpha and radiation, when used as single modalities, decreased LS174T cell viability with time. However, treatment with TNF-alpha before irradiation resulted in highly significant reductions in 3H-TdR uptake and decreased clonogenic survival compared to their counterparts receiving only radiation. Our data show that these two measurements of tumour-cell damage correlate well. No difference was noted in vital dye exclusion when comparisons were made between TNF-alpha+radiation and radiation alone. This latter finding may be partly due to the fact that although apoptotic cells are 'dead', they generally do not become more permeable to normally excluded macromolecules. Chemiluminescence measurements indicate that the radiation-enhancing mechanism of TNF-alpha may be related to oxygen radical production by the LS174T cells. Taken together our results suggest that TNF-alpha may be useful as an adjunctive modality in the radiotherapy of colon cancer.

Single-chain antibody molecules were expressed from modified eukaryotic expression vectors as individual protein domains encoded on interchangeable cDNA cassettes. Two different single-chain antibody derivatives were constructed by linking individual light- and heavy-chain variable domains. The first was specific for the L6 tumour-associated antigen and the second was specific for human CD3. Each single-chain variable domain was genetically fused with an Fc 'tag' and expressed as a fusion protein in a COS cell transient transfection system. These single-chain antibody derivatives demonstrated specific binding to cells expressing appropriate antigen and bound with affinities similar to native antibody. The CD3 single chain molecule mediated stronger activation of PLC gamma 1 and similar levels of T-cell proliferation compared with native antibody. A bispecific Fv single-chain cassette was created by fusing the expression cassettes encoding the binding domains for L6 and CD3 single-chain molecules using oligonucleotide primers encoding a short 27-residue 'helical' peptide linker. The CD3-L6 variable domains were fused to the Fc tag and expressed in COS cells. The CD3-L6FvIg bispecific fusion protein mediated adhesion between T cells and L6-positive tumour cells, and stimulated potent T-cell proliferation and cytotoxicity against tumour cells expressing the L6 antigen.

Athymic (Swiss nude) and euthymic (DBA) tumour-bearing mice were injected intravenously with various vaccinia virus (Copenhagen strain) recombinants. Several days after inoculation, tumour cells were found to be well infected with infective vaccinia particles, while organs such as liver, spleen, brain and bone marrow showed barely detectable levels or no signs at all of virus infection. Injection of tumour bearing mice with recombinant VV harbouring the cDNA for either huIL-2 or muIL-6 resulted in detectable lymphokine in the sera of injected animals. Injection of tumour-bearing nude mice with VV-IL-6, but not with VV-IL-2, resulted in significant reduction in growth rate of the tumour, and in some cases, complete rejection of the tumour. Tumour-bearing euthymic mice responded differently. Intravenous injection of VV-IL-2, but not VV-IL-6 resulted in reduced growth rate of 50% of tumours and complete rejection of 17% of tumours.

Recent advances in elucidating the activation and regulation of the autoimmune processes have provided new approaches for selective immunotherapy. Three different strategies are described: autoantigen-based therapy utilizing immunospecifically designed macromolecules and peptides, T-suppressor lines and clones, as well as antibodies specific to the antigen-MHC complex. These modalities, the efficacy of which has been demonstrated for experimental allergic encephalomyelitis, may be adapted to other experimental as well as human autoimmune diseases.