Interaction between C3 and IL-2; inhibition of C3b binding to CR1 by IL-2

Immunol Lett. 1989 May;21(2):131-7. doi: 10.1016/0165-2478(89)90049-7.

Abstract

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.

MeSH terms

  • Cell Line
  • Complement C3 / physiology*
  • Complement C3b / metabolism*
  • Concanavalin A / metabolism
  • Enzyme-Linked Immunosorbent Assay
  • Humans
  • Interleukin-2 / physiology*
  • Ligands
  • Receptors, Complement / metabolism*
  • Rosette Formation
  • Sepharose / metabolism
  • T-Lymphocytes, Helper-Inducer / metabolism

Substances

  • Complement C3
  • Interleukin-2
  • Ligands
  • Receptors, Complement
  • Concanavalin A
  • Complement C3b
  • Sepharose