A significant proportion of previously activated human T cells undergo apoptosis when triggered through the CD3/T cell receptor complex, a process termed activation-induced cell death (AICD). Ligation of Fas on activated T cells by either Fas antibodies or recombinant human Fas-ligand (Fas-L) also results in cytolysis. We demonstrate that these two pathways of apoptosis are causally related. Stimulation of previously activated T cells resulted in the expression of Fas-L mRNA and lysis of Fas-positive target cells. Fas-L antagonists inhibited AICD of T cell clones and staphylococcus enterotoxin B (SEB)-specific T cell lines. The data indicate AICD in previously stimulated T cells is mediated by Fas/Fas-L interactions.

/pdf/fas-ligand-mediates-activation-induced-cell-death-in-human-t-iore646k8z.pdf

Fas ligand mediates activation-induced cell death in human T lymphocytes.

https://www.cell.com/cell/pdf/0092-8674(93)90457-2.pdf

Molecular regulation of apoptosis: Genetic controls on cell death

Heat shock proteins and the immune response

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(03)14075-5.pdf

Heat shock proteins as regulators of the immune response

Ankylosing spondylitis (AS) is a complex, potentially debilitating disease that is insidious in onset, progressing to radiological sacroiliitis over several years. Patients with symptomatic AS lose productivity owing to work disability and unemployment, have a substantial use of healthcare resources, and reduced quality of life. The pathogenesis of AS is poorly understood. However, immune mediated mechanisms involving human leucocyte antigen (HLA)-B27, inflammatory cellular infiltrates, cytokines (for example, tumour necrosis factor α and interleukin 10), and genetic and environmental factors are thought to have key roles. The detection of sacroiliitis by radiography, magnetic resonance imaging, or computed tomography in the presence of clinical manifestations is diagnostic for AS, although the presence of inflammatory back pain plus at least two other typical features of spondyloarthropathy (for example, enthesitis and uveitis) is highly predictive of early AS. Non-steroidal anti-inflammatory drugs (NSAIDs) effectively relieve inflammatory symptoms and are presently first line drug treatment. However, NSAID treatment has only a symptomatic effect and probably does not alter the disease course. For symptoms refractory to NSAIDs, second line treatments, including corticosteroids and various disease modifying antirheumatic drugs, are employed but are of limited benefit. Emerging biological therapies target the inflammatory processes underlying AS, and thus, may favourably alter the disease process, in addition to providing symptom relief.

https://ard.bmj.com/content/annrheumdis/61/suppl_3/iii8.full.pdf

Ankylosing spondylitis: an overview.

Bacterial Ag, especially those of mycobacteria, have been implicated in the pathogenesis of experimental inflammatory arthritis in rodents, while in man, reactive arthritis has a clear temporal relationship to infection with particular bacteria. To investigate the role of immune responses to bacterial Ag in inflammatory arthritis, we have examined the proliferative responses of paired synovial fluid and PBMC when stimulated with 1) suspensions of irradiated or heat-killed bacteria associated with reactive arthritis (ReA), 2) purified protein derivative, 3) a recombinant 65-kDa heat shock protein of Mycobacterium leprae. The 65-kDa Ag was stimulatory to synovial fluid mononuclear cells, but not PBMC, from patients with different arthropathies, including most of those with ReA, but also some with rheumatoid arthritis. Furthermore, the magnitude of these responses correlated more closely with responses to ReA-associated bacteria (such as Salmonella), than with responses to the mycobacterial Ag represented in purified protein derivative. These results suggest that the 65-kDa molecule, which is common to a wide range of bacteria, may be an important immunogen for the T cell-mediated immune responses within the joint in different clinically defined inflammatory arthropathies.

In vitro responses to a 65-kilodalton mycobacterial protein by synovial T cells from inflammatory arthritis patients.

Adjuvant arthritis in rats is induced by a T cell clone specific for amino acids 180-188 of the mycobacterial 65-kD heat-shock protein, and synovial T cell responses to this same Ag have been noted in human arthritis. We have isolated 65-kD Ag-specific T cell clones from synovial fluid mononuclear cells of a patient with acute arthritis, which, unlike the corresponding PBMC, showed a marked proliferative response to the 65-kD Ag. Using synthetic peptides corresponding to the whole sequence of the 65-kD Ag, all the clones were shown to recognize an epitope present in the first NH2-terminal peptide (amino acids 1-15), with no response to the adjacent peptide (amino acids 6-22) or to any other peptide. The complete dominance of this epitope in the response to the 65-kD Ag was shown by documenting responses to the peptide in PBMC obtained after recovery from the arthritis. This epitope, like that recognized by the rat arthritogenic T cell clone, is in a portion of the 65-kD sequence that is not conserved between bacteria and eukaryotes, so that in this case, joint inflammation could not be attributed to bacteria-induced T cell clones cross-reacting with the self 65-kD Ag.

https://rupress.org/jem/article-pdf/171/3/831/1100107/831.pdf

Recognition of a mycobacteria-specific epitope in the 65-kD heat-shock protein by synovial fluid-derived T cell clones.

Reactive arthritis (ReA) is believed to be "triggered' by infection with certain bacteria. When the proliferative responses of mononuclear cells (MC) obtained from the synovial fluid (SF) of ReA patients were examined, it was found that they responded maximally to the specific organism responsible for the preceding infection. The response was shown to be due to Class II MHC-restricted T cells by inhibition experiments using cyclosporin A and monoclonal antibodies. Significant SFMC responses to additional organisms associated with ReA were also recorded; since there was no serological evidence of preceding infection by these organisms, this finding suggests that these bacteria share common T cell-recognized antigenic epitopes. The corresponding responses by peripheral blood mononuclear cells (PBMC) were much lower and often barely detectable, whereas their responses to PHA were consistently higher than those of SFMC. These results, combined with evidence that bacterial antigens localize in the joint, indicate that a bacteria-specific, T-cell-mediated response may play a central role in the pathogenesis of ReA.

Synovial T lymphocyte recognition of organisms that trigger reactive arthritis.

Synovial fluid (SF) mononuclear cells from patients with reactive arthritis (ReA) proliferate in vitro when challenged with ReA-associated bacteria, the maximal response being for the organism causing the triggering infection. We report the results of a study of the antigenic specificity of synovial T lymphocytes from an HLA–B27 positive ReA patient whose SF mononuclear cells responded preferentially to Yersinia antigens. This is the first report of the isolation of Yersinia-specific T cell clones from synovial membrane (obtained by closed-needle synovial biopsy). We present a detailed analysis of these clones, together with others obtained from the SF.

Isolation of Yersinia-specific T cell clones from the synovial membrane and synovial fluid of a patient with reactive arthritis.

We and others have previously shown that synovial fluid (SF) mononuclear cells (MC) from patients with both reactive arthritis and other inflammatory arthritides proliferate in vitro in response to bacteria clinically associated with the triggering of reactive arthritis. In all cases, such SFMC responses are greater than the corresponding peripheral blood (PB) MC responses, often markedly so, and the mechanism for this is unclear. We have investigated this phenomenon by comparing the relative abilities of irradiated non-T cells derived from PB and SF to support autologous T cell responses to ReA-associated bacteria. Seven patients whose SFMC had been shown previously to respond to bacteria were studied. We demonstrate antigen-specific responses of PB T cells to bacteria in the presence of SF non-T cells which are in marked contrast to the minimal responses of either unfractionated PBMC or PB T cells reconstituted with PB non-T cells. We also show that PB, but not SF T cells respond strongly to autologous SF non-T cells in the absence of antigen or mitogen. These findings demonstrate that SF antigen-presenting cells (APC) are potent activators of PB T cells. We conclude that the contrasting responses of SFMC and PBMC to bacterial antigens may be accounted for at least in part by an enhanced ability of SF APC to support T cell proliferative responses.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2249.1990.tb05177.x

J. S. H. Gaston

Papers

In vitro responses to a 65-kilodalton mycobacterial protein by synovial T cells from inflammatory arthritis patients.

Recognition of a mycobacteria-specific epitope in the 65-kD heat-shock protein by synovial fluid-derived T cell clones.

Synovial T lymphocyte recognition of organisms that trigger reactive arthritis.

Isolation of Yersinia-specific T cell clones from the synovial membrane and synovial fluid of a patient with reactive arthritis.

Synovial fluid antigen-presenting cells unmask peripheral blood T cell responses to bacterial antigens in inflammatory arthritis.