The cathepsin B inhibitor, z-FA-FMK, inhibits human T cell proliferation in vitro and modulates host response to pneumococcal infection in vivo |
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Authors: | Lawrence Clare P Kadioglu Aras Yang Ai-Li Coward William R Chow Sek C |
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Affiliation: | Medical Research Council Toxicology Unit, University of Leicester, Leicester, United Kingdom. |
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Abstract: | The cathepsin B inhibitor, benzyloxycarbonyl-phenyl-alanyl-fluoromethylketone (z-FA-FMK) at nontoxic doses was found to be immunosuppressive and repressed human T cell proliferation induced by mitogens and IL-2 in vitro. We showed that z-FA-FMK suppresses the secretion of IL-2 and IFN-gamma as well as the expression of IL-2R alpha-chain (CD25) in activated T cells, whereas the expression of the early activated T cell marker, CD69, was unaffected. Furthermore, z-FA-FMK blocks NF-kappaB activation, inhibits T cell blast formation, and prevents cells from entering and leaving the cell cycle. z-FA-FMK inhibits the processing of caspase-8 and caspase-3 to their respective subunits in resting T cells stimulated through the Ag receptor, but has no effect on the activation of these caspases during Fas-induced apoptosis in proliferating T cells. When administered in vivo, z-FA-FMK significantly increased pneumococcal growth in both lungs and blood, compared with controls, in a mouse model of intranasal pneumococcal infection. Because host response to bronchopneumonia in mice is T cell dependent, our collective results demonstrated that z-FA-FMK is immunosuppressive in vitro and in vivo. |
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