Increase of cytokine production by pulmonary artery endothelial cells induced by supernatants from monocytes stimulated with autoantibodies against U1-ribonucleoprotein.
OBJECTIVE
To clarify the pathogenetic role of autoantibodies against U1-RNP (ribonucleoprotein) (anti-U1-RNP) in mixed connective tissue disease (MCTD), we examined whether supernatants of monocytes which were stimulated with anti-U1-RNP could induce the production of proinflammatory cytokines by human pulmonary artery endothelial cells (HPAECs).


METHODS
Monocytes from MCTD patients (n = 11) and normal volunteers (n = 11) were stimulated with purified antibodies against U1-RNP or double-stranded DNA and their supernatants were added to cultures of HPAECs. Cell-associated cytokines were assayed by an enzyme-linked immunosorbent assay.


RESULTS
The supernatants of anti-U1-RNP-stimulated MCTD monocytes significantly up-regulated the cell-associated production of IL-1 alpha (p < 0.01) and IL-6 (p < 0.01) by HPAECs compared with their production by normal IgG-stimulated MCTD monocytes, whereas the cell-associated production of IL-1 beta and TNF-alpha by HPAECs was not up-regulated. The supernatants of anti-U1-RNP-stimulated monocytes from normal volunteers similarly up-regulated the cell-associated production by HPAECs of IL-1 alpha (p < 0.01) and IL-6 (p < 0.01), but not of IL-1 beta and TNF-alpha. Supernatants of monocytes stimulated with the F(ab')2 preparation of anti-U1-RNP antibodies enhanced the amounts of both Il-1 alpha and IL-6 associated with HPAECs almost as effectively as those stimulated with intact autoantibody molecules. Inhibition experiments employing specific anti-cytokine antibodies of anti-U1-RNP-stimulated monocyte supernatants suggested that soluble factors, including cytokines, in monocyte supernatants could enhance the cytokine association with HPAECs.


CONCLUSIONS
Up-regulation by anti-U1-RNP autoantibodies of proinflammatory cytokines associated with vascular endothelial cells may play a role in the immunopathological processes leading to proliferative vasculopathy, a characteristic of MCTD.
Okawa-Takatsuji
M
M
Division of Clinical Immunology, International Medical Center of Japan, Tokyo, Japan. okawat@ri.imcj.go.jp
Aotsuka
S
S
Uwatoko
S
S
Kinoshita
M
M
Sumiya
M
M
D001323:Autoantibodies / Q000494:pharmacology*; D002478:Cells, Cultured; D017077:Culture Media, Conditioned; D016207:Cytokines / Q000096:biosynthesis*; D004730:Endothelium, Vascular / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D008947:Mixed Connective Tissue Disease / Q000097:blood*; D009000:Monocytes / Q000187:drug effects / Q000502:physiology*; D011651:Pulmonary Artery / Q000378:metabolism*; D017412:Ribonucleoprotein, U1 Small Nuclear / Q000276:immunology*; D015854:Up-Regulation
D001323:Autoantibodies; D017077:Culture Media, Conditioned; D016207:Cytokines; D017412:Ribonucleoprotein, U1 Small Nuclear