Signaling through the EBV/C3d receptor (CR2, CD21) in human B lymphocytes: activation of phosphatidylinositol 3-kinase via a CD19-independent pathway.

We herein analyzed the regulation of phosphatidylinositol 3-kinase (PI 3-kinase) activity by CR2 activated on B lymphocyte cell surface. We demonstrated that CR2 activation triggered in vivo PI 3-kinase activity and interaction of PI 3-kinase p85 subunit with a tyrosine-phosphorylated p95 component. The specificity of PI 3-kinase activity was controlled using wortmannin and LY294002.

Tyrosine phosphorylation in peripheral lymphocytes from patients with systemic lupus erythematosus.

A comparative study of tyrosine phosphorylation was performed on peripheral blood lymphocytes from systemic lupus erythematosus (SLE) patients and from healthy donors. Freshly isolated SLE lymphocytes presented an elevated tyrosine phosphorylation level when compared to healthy donors lymphocytes (p = 0.005).

Pep34, a synthetic peptide whose sequence corresponds to the intracytoplasmic domain of the Epstein-Barr virus receptor (CR2, CD21), regulates human B lymphocyte proliferation triggered through CR2.

CR2 is involved in regulation of human B lymphocyte proliferation by interacting, through distinct domains, with extracellular, cell surface or intracellular components. Contribution of CR2 intracytoplasmic domain in CR2 regulatory functions remains unclear. Thus, we used pep34, a 34 amino acid synthetic peptide whose sequence corresponds to CR2 intracytoplasmic domain.

Epstein-Barr virus/C3d receptor (CR2, CD21) activated by its extracellular ligands regulates pp105 phosphorylation through two distinct pathways.

We previously demonstrated that human C3d or pep16, a 16-amino acid synthetic peptide derived from human C3d, induced in vivo and in vitro tyrosine phosphorylation of pp105, an intracellular component found only in human cells that express CR2 at their surface. To determine the contribution of CR2 molecules to this enzymatic regulation, we first analyzed whether activation of CR2 by other extracellular CR2 ligands could trigger such regulation in cell extracts. Subsequently, we used cell extracts of either CR2-positive cells depleted in CR2 molecules by absorption with anti-CR2 antibodies or CR2-negative cells transfected with CR2 cDNA.