Biological function and distribution of human interleukin-12 receptor beta chain.
We previously described the cloning of a cDNA encoding an interleukin-12 receptor (IL-12R) subunit, designated beta, that bound IL-12 with low affinity when expressed in COS cells. We now report that a pair of monoclonal antibodies (mAb), 2B10 and 2.4E6, directed against different epitopes on the IL-12R beta chain, when used in combination, strongly inhibited IL-12-induced proliferation of activated T cells, IL-12-induced secretion of interferon-gamma by resting peripheral blood mononuclear cells (PBMC), and IL-12-mediated lymphokine-activated killer cell activation. The mAb had no effect on lymphoblast proliferation induced by IL-2, -4, or -7. Thus, the IL-12R beta chain appears to be an essential component of the functional IL-12R on both T and natural killer (NK) cells. We previously observed that high affinity IL-12R were expressed on activated T and NK cells, but not B cells. Studies using flow cytometry and reverse transcription-polymerase chain reaction analysis showed that IL-12R beta chain was expressed on several human T, NK, and (surprisingly) B cell lines, but not on non-lymphohematopoietic cell lines. The Kit225/K6 (T cell) and SKW6.4 (B cell) lines were found to express the greatest amounts of IL-12R beta chain (800-2500 sites/cell); however, Kit225/K6 but not SKW6.4 cells bound IL-12. Similar to SKW6.4 B cells, activated tonsillar B lymphocytes expressed IL-12R beta chain but, consistent with previous results, did not display detectable IL-12 binding. Likewise, up to 72% of resting PBMC from normal volunteer donors expressed IL-12R beta, but did not bind measurable amounts of IL-12. These results indicate that expression of IL-12R beta is essential, but not sufficient, for expression of functional IL-12R. We speculate that expression of functional, high-affinity IL-12R may require the presence of a second subunit that is more restricted in its expression than IL-12R beta.
Wu
C Y
CY
Department of Inflammation/Autoimmune Diseases, Hoffmann-La Roche Inc., Nutley, USA.
Warrier
R R
RR
Carvajal
D M
DM
Chua
A O
AO
Minetti
L J
LJ
Chizzonite
R
R
Mongini
P K
PK
Stern
A S
AS
Gubler
U
U
Presky
D H
DH
Gately
M K
MK
D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001402:B-Lymphocytes / Q000276:immunology; D001483:Base Sequence; D001665:Binding Sites / Q000276:immunology; D001667:Binding, Competitive / Q000276:immunology; D002460:Cell Line; D002469:Cell Separation; D006801:Humans; D018664:Interleukin-12 / Q000737:chemistry / Q000378:metabolism*; D007963:Leukocytes, Mononuclear / Q000737:chemistry* / Q000276:immunology; D008213:Lymphocyte Activation; D008969:Molecular Sequence Data; D014066:Palatine Tonsil / Q000166:cytology; D018123:Receptors, Interleukin / Q000276:immunology / Q000378:metabolism* / Q000502:physiology*; D053707:Receptors, Interleukin-12
D000911:Antibodies, Monoclonal; D018123:Receptors, Interleukin; D053707:Receptors, Interleukin-12; D018664:Interleukin-12