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LT May, K Patel, D Garcia, MI Ndubuisi, S Ferrone, A Mittelman, A Mackiewicz and PB Sehgal
Department of Microbiology and Immunology, New York Medical College,
Valhalla 10595.
In a phase 1 study of recombinant interleukin-6 (rIL-6) in patients with
advanced solid tumors (n = 15), we discovered that the endogenous IL-6
levels, in pretreatment plasma or serum samples, were distributed into two
groups. One set of patients (designated "type 1"; n = 9) was characterized
by low plasma IL-6 levels (48 to 1,700 pg/mL) as measured using
enzyme-linked immunosorbent assays (ELISA) for IL-6. In the second set of
patients (designated "type 2"; n = 6), IL-6 ELISAs showed high levels of
plasma IL-6 (50 to 600 ng/mL). Neither group had detectable B9 hybridoma
cell growth factor activity associated with the IL-6 in their pretreatment
plasma or serum. Plasma C-reactive protein (CRP) levels were markedly
elevated in type II patients suggesting that the circulating IL-6 was
biologically active in vivo. In both groups of patients there was a small
but significant increase in B9 activity in the plasma within three hours
after rIL-6 administration (n = 5). Gel filtration profiles showed that
circulating IL-6 in type 1 patients, 15 to 120 minutes after rIL-6
administration was of approximate mass 20 to 40 kD, whereas in type 2
patients, the IL-6 before and after exogenous rIL-6 administration was
indistinguishable and was of an approximate mass of 200 kD. IL-6
immunoaffinity purification of the 200 kD complexes showed these to contain
multiple isoforms of IL-6 (14 to 31 kD) and the soluble IL-6 receptor
(sIL-6R; 50 to 55 kD). A distinguishing clinical history was that all of
the type 2 patients had been actively immunized with an anti-idiotypic
monoclonal antibody (MoAb) (MK2-23) 3 to 12 months before initiation of
this study for advanced melanoma. An analysis of the plasma IL-6 content in
other melanoma patients (n = 16) during antiidiotypic MoAb immunization
indicated that marked (up to 600 ng/mL) and sustained (several months)
elevations of circulating "chaperoned" IL-6 were induced by active
immunization regimens.
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| Copyright © 1994 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||