Human soluble IL-6 receptor: its detection and enhanced release by HIV infection.
By using a fluorescence sandwich ELISA for the quantification of soluble human IL-6R, normal human PBMC were found to be induced to release IL-6R into culture supernatant by stimulation with PHA. Furthermore, certain promonocyte cell lines and human T-cell leukemia virus I (HTLV-I)-positive cell lines produced sIL-6R into culture supernatants constitutively. However, this was not found with HTLV-I negative T cell lines and Burkitt's B cell line. In addition, generation of supernatant IL-6R of the promonocyte cell line was significantly increased 27-fold after PMA treatment and sevenfold after infection with HIV. The released IL-6R molecules were characterized as an apparent m.w. of 50 to 55 kDa by both size-exclusion HPLC and immunoprecipitation of the soluble protein with IL-6R-specific mAb followed by SDS-PAGE analysis. Furthermore, increased levels of serum IL-6R were detected in blood donors seropositive for HIV. Moreover, the released IL-6R could bind efficiently to purified rIL-6 on solid phase and suppressed the proliferative responses of PBMC. These results suggest that the release of soluble IL-6R might be linked to regulatory functions of immune responses induced by IL-6 stimulation during normal and human retrovirus-infected cell growth and differentiation.
Honda
M
M
Laboratory of Immunology, National Institute of Health, Tokyo, Japan.
Yamamoto
S
S
Cheng
M
M
Yasukawa
K
K
Suzuki
H
H
Saito
T
T
Osugi
Y
Y
Tokunaga
T
T
Kishimoto
T
T
D004797:Enzyme-Linked Immunosorbent Assay; D015658:HIV Infections / Q000276:immunology*; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism*; D008213:Lymphocyte Activation; D008970:Molecular Weight; D011971:Receptors, Immunologic / Q000032:analysis* / Q000276:immunology / Q000378:metabolism; D019947:Receptors, Interleukin-6
D015850:Interleukin-6; D011971:Receptors, Immunologic; D019947:Receptors, Interleukin-6