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- Title
Antigen-bound C3b and C4b enhance antigen-presenting cell function in activation of human T-cell clones.
- Authors
Arvieux, J.; Yssel, H.; Colomb, M. G.
- Abstract
The effect of complement fragments C3b and C4b, on the triggering of antigen-specific human T-cell clones by Epstein-Barr virus-transformed human lymphoblastoid 13 cells (LCL) when these fragments are covalently coupled to the antigen tetanus toxin (TT) is described. TT was chemically cross-linked to purified C3b [(TT-C3b)n], C4b [(TT-C4b)n] or bovine serum albumin [(TT-BSA)n] as a control. T-cell activation was quantified by tritiated thymidine incorporation and 51Cr release. (TT- C3b)n and ( TT-C4b)n induced proliferative responses comparable to (TT-BSA)n but at 18-25 and 4- 6 lower concentrations, respectively. This enhancing effect required the covalent cross-linking of the complement fragments to the antigen and involved intracellular processing of the latter by LCL. Antigen presentation was similarly enhanced when measuring the cytotoxic activity of a helper T-cell clone against LCL previously pulsed with (TT-C3b)n or (TT-C4b)n compared with (TT-BSA)n. Binding studies, carried out on LCL using TT radiolabelled with 125I before cross-linking, indicated that (TT-C3b)n and (TT-C4b)n gave three- to four-fold more binding than (TT-BSA)n. Addition of antibodies against CR! and CR2 or proteolytic removal of these complement receptors with trypsin inhibited by about 60% the enhancing effect of TT-bound C3b and C4b in both binding and functional assays. These results indicate that binding of C3b or C4b to antigen enhances antigen- specific proliferative and cytotoxic responses of T cells by targeting opsonized antigen onto complement receptors CR 1 and CR2 of LCL. The putative significance of these findings in terms of regulation of immune responses by complement is discussed.
- Subjects
ANTIGENS; CELL physiology; T cells; CLONE cells; IMMUNOGLOBULINS; CELL proliferation
- Publication
Immunology, 1988, Vol 65, Issue 2, p229
- ISSN
0019-2805
- Publication type
Article