We have investigated the suppressive effect of human natural killer (NK) cells on autologous B-cell proliferation. Removal of NK cells by anti-NK-cell monoclonal antibodies (CD16, Leu 11b; Leu 7) increased by 2-3-fold the proliferative response of purified B cells activated by anti-mu and B-cell growth factor (BCGF). The inhibitory effect of NK cells was observed using recombinant IL-2 or semi-purified BCGF-I as sources of BCGF. Moreover NK cells, highly purified by centrifugation on a Percoll discontinuous density gradient, suppressed the proliferative response of purified autologous B cells activated by anti-mu and BCGF. These results show a suppressive effect of human NK cells on B-cell proliferation in vitro.

Antibodies, Monoclonal↗

PubMedDate not supplied

Interleukin-6 is the central tumor growth factor in vitro and in vivo in multiple myeloma.

When bone-marrow cells from patients with multiple myeloma (MM) were seeded in short-term cultures, a spontaneous proliferation of the myeloma cells occurred for most of the patients with active disease and proliferating myeloma cells in vivo. In all cases, this spontaneous proliferation was inhibited by anti-IL-6 monoclonal antibodies (mabs). Moreover, myeloma cell lines, completely dependent upon exogenous IL-6 for their growth, could be reproducibly established by initially stimulating the myeloma cells with both IL-6 and GM-CSF. These results demonstrate that IL-6 is a major paracrine myeloma-cell growth factor in vitro. High serum IL-6 levels were observed in MM patients with active disease, especially patients with terminal disease. High IL-6 mRNA levels were found in bone-marrow cells of MM patients, mainly in myeloid and monocytic cells, in vivo. The myeloma cells did not express IL-6 mRNA. Injection of anti-IL-6 mabs to MM patients with terminal disease and extramedullary proliferation, completely blocked the myeloma-cell proliferation in vivo and completely inhibited the serum IL-6 bioactivity and the serum CRP levels. One patient with plasma cell leukemia and hypercalcemia was treated for two months with anti-IL-6 mabs and maintain in remission for 2 months without major side effects. Interestingly, the serum calcium levels also decreased in these patients. All these results show that IL-6 is the main cytokine responsible not only for the myeloma-cell proliferation in vivo, but presumably also for the large bone resorption processes observed in human MM.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

Epitope analysis of human IL-6 receptor gp80 molecule with monoclonal antibodies.

Gp80 human IL-6R was studied using 7 murine mAb (M37, M91, M113, M139, M164, M182 and M195) obtained after fusion of splenocytes of Balb/c mice immunised with a mixture of recombinant IL-6 receptor (rIL-6R) and cells from 2 cell lines expressing IL-6R. These were U266, which is IL-6 independent and XG-1 which is IL-6-dependent. In ELISA the 7 mAb reacted against the rIL-6R and against the natural soluble form found in plasma (nIL-6R), which both lack transmembrane and cytoplasmic domains. However, M195 reacted less with the natural than with the recombinant soluble IL-6R. Using FACS analysis, the 7 mAb were shown to bind to U266 cells but not to the Namalva cell line which is deprived of IL-6R. This showed that they all recognised the membrane form of the IL-6R. Three of the anti-IL-6R mAb reacted with rIL-6R by Western blotting. Four different epitopes of the molecule were identified, either by cross-blocking experiments of mAb binding to IL6R in ELISA or by the biosensor Biacore technology. A group of 4 mAb (M37, M113, M139 and M164) and another mAb (M195) identified 2 different epitopes involved in IL-6 binding. These antibodies were able to inhibit the binding of IL-6 to IL-6R and the proliferation of the IL-6-dependent XG-1 cell line. M91 and M182 recognized 2 other epitopes that were not involved in IL-6 binding. As expected, M91 did not inhibit XG-1 proliferation; in contrast, M182 interfered with the proliferative response of the XG-1 cell line.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗