Polymyositis (PM) and dermatomyositis (DM) are the prototypical inflammatory diseases of skeletal muscle. In PM, CD8 ϩ T cells invade and destroy muscle fibers, whereas humoral effector mechanisms prevail in DM. We studied the expression of the cytotoxic mediator perforin in inflammatory cells in PM and DM muscle by semiquantitative PCR, immunohistochemistry and confocal laser microscopy. Similar levels of perforin mRNA were expressed in PM and DM, and abundant perforin-expressing CD3 ϩ CD8 ϩ and CD3 ϩ CD4 ϩ T cells were observed in both diseases. However, there was a striking difference in the intracellular localization of perforin. In DM, perforin was distributed randomly in the cytoplasm of the inflammatory T cells. In contrast, 43% of the CD8 ϩ T cells that contacted a muscle fiber in PM showed perforin located vectorially towards the target muscle fiber. The results suggest ( a ) that the random distribution of perforin in the cytoplasm of muscle-infiltrating T cells observed in DM reflects nonspecific activation, and ( b ) that the vectorial orientation observed only in PM reflects the specific recognition via the T cell receptor of an antigen on the muscle fiber surface, pointing to a perforin-and secretion-dependent mechanism of muscle fiber injury. ( J. Clin. Invest. 1996. 97:2905-2910.)

T-cells and monocytes are the first cells infiltrating the arterial intima during the early stages of atherogenesis. Recently our laboratory has provided evidence that T-cells isolated from atherosclerotic intima reacts against heat shock protein 60 (Hsp60). Transmigration of activated T-cells into the intima is mediated by adhesion molecules (ICAM-1; VCAM-1; ELAM-1) expressed on activated endothelial cells. Here we studied the potential of cytokines (TNF-alpha, IFN-gamma, IL-1). Escherichia coli lipopolysaccharide (LPS), native and oxidized low-density lipoprotein (LDL; oxLDL) and high temperature to induce adhesion molecules as well as Hsp60 and Hsp70 expression in human endothelial cells (EC). On Northern blots, a strong signal for ICAM-1, VCAM-1 and ELAM-1 was detected after 4 h, which thereafter declined, but did not reach the basal level of untreated control cells. Heat shock induced the expression of Hsp60 and Hsp70 but not of adhesion molecules. EC were cultivated in serum-free medium, which led to the expression of adhesion molecule transcripts. Addition of LDL or oxLDL to these ECs did not alter the expression of these transcripts. The production of adhesion molecule proteins was analysed by flow cytometry. In human venous endothelial cells (HVEC) and human arterial endothelial cells (HAEC) ICAM-1 and VCAM-1 production was permanently highly induced, whereas the high level of ELAM-1 production at 4 h disappeared after 24 h. Furthermore, only HAEC, but not HVEC, produced ICAM-1, VCAM-1 and ELAM-1 after stress by moderately and highly oxLDL. LDL and oxLDL did not induce the production of Hsp60 and Hsp70. The present study demonstrates the co-expression of Hsp60 and adhesion molecules in arterial and venous EC in response to cytokine and LPS exposure, and that oxLDL is an efficient inducer of adhesion molecules in arterial EC and not in venous EC. These features provide the prerequisites for a cellular immune reaction against Hsp60 expressed by stressed EC in the initial stages of atherosclerosis.

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Human myoblasts, cultured from muscle and purified to greater than 95%, were investigated for their capacity to act as facultative APC. The myoblasts reacted with antidesmin mAb and had the capacity to fuse into multinucleated myotubes in appropriate medium. The expression of HLA class I, HLA-DR, HLA-DP, HLA-DQ, intercellular adhesion molecule-1 (ICAM-1/CD54), lymphocyte function-associated (LFA) molecules LFA-1 (CD11a/CD18), LFA-2 (CD2), and LFA-3 (CD58) was investigated by FACS analysis before and after induction for various times with human rIFN-gamma, TNF-alpha, or both. Without cytokine induction, myoblasts expressed only HLA-class I and LFA-3. IFN-gamma alone or in combination with TNF-alpha induced the expression of HLA-DR and ICAM-1 reaching a plateau after 48 h, followed by HLA-DP and even later HLA-DQ. TNF-alpha alone induced only ICAM-1. The functional capacity of myoblasts to present Ag to CD4+ T cells was investigated using autologous T cell lines specific for tuberculin, tetanus toxoid, and human myelin basic protein. Noninduced myoblasts or myoblasts treated with TNF-alpha alone could not present any of these Ag to the T cells. However, myoblasts treated with IFN-gamma induced Ag-specific proliferation. In the presence of relevant Ag, myoblasts were killed by the T cells as observed by microscopy and measured by 51Cr release. Ag-specific T cell proliferation and myoblast killing was inhibited in the presence of anti-DR mAb. These results suggest that human myoblasts may act as facultative APC during local immune reactions in muscle.

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