Interaction between C3 and IL-2; inhibition of C3b binding to CR1 by IL-2.
We previously reported that C3 has a role in the enhancement of the IL-2 dependent proliferation of helper T cells. Because the IL-2R has a structural homology with the complement proteins, such as CR1 and CR2, we studied the possible ligand crossreactions on CR1 and IL-2-receptor, and the direct interaction between C3 and IL-2. While C3 has an enhancing effect on the IL-2 dependent proliferation of HT-2, a CR1-positive mouse T-cell line, the growth of the CTLL-16 line (CR1-negative) is not affected by C3. It has been proven that neither the insolubilized C3 nor the soluble C3b-like C3 react with the IL-2 binding epitope of the IL-2 receptor. However, using human RBC we have demonstrated that the binding of aggregated C3 to CR1 is inhibited by rIL-2, in a dose-dependent manner. When RBC were incubated with rIL-2 and FITC-labelled Fab-anti-CR1 simultaneously, there was no inhibition in the fluorescence intensity. As detected by ELISA, rIL-2 was bound to the same extent by insolubilized C3, C3b, and C3c, while C3d coat had lower binding capacity. The receptor-binding epitope of IL-2 is intact in the complex of complement proteins and rIL-2, as demonstrated by the binding of DMS1, a monoclonal antibody reacting with the receptor site of IL-2. It is strongly suggested that C3b may play a role in the growth of CR1 positive T cells.
Bartók
I
I
Department of Immunology, L. Eötvös University, Göd, Hungary.
Erdei
A
A
Mouzaki
A
A
Osawa
H
H
Szölösi
J
J
Eigentler
A
A
Diamantstein
T
T
Dierich
M P
MP
Gergely
J
J
D002460:Cell Line; D003176:Complement C3 / Q000502:physiology*; D003179:Complement C3b / Q000378:metabolism*; D003208:Concanavalin A / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007376:Interleukin-2 / Q000502:physiology*; D008024:Ligands; D011951:Receptors, Complement / Q000378:metabolism*; D012397:Rosette Formation; D012685:Sepharose / Q000378:metabolism; D006377:T-Lymphocytes, Helper-Inducer / Q000378:metabolism
D003176:Complement C3; D007376:Interleukin-2; D008024:Ligands; D011951:Receptors, Complement; D003208:Concanavalin A; D003179:Complement C3b; D012685:Sepharose