The complement receptor 3, CR3 (CD11b/CD18), on T lymphocytes: activation-dependent up-regulation and regulatory...

Area of Science:

• Immunology
• Cell Biology

Background:

• Complement receptor 3 (CR3; CD11b/CD18) is primarily found on leukocytes like NK cells, monocytes, and neutrophils.
• While T cells typically express low levels of CD11b, particularly CD8+ cells, its expression can be modulated.

Purpose of the Study:

• To investigate the expression and functional role of CR3 (CD11b/CD18) on T lymphocytes.
• To determine if CR3 expression on T cells is activation-dependent and influences T cell proliferation and cytokine release.

Main Methods:

• Flow cytometry was used to analyze CD11b expression on peripheral T lymphocytes and T cell lines.
• T cell proliferation and IL-2 release were measured following stimulation with anti-CD3/IL-2 or mononuclear cells/mitogen, with and without CR3-targeting antibodies or ligands.

Main Results:

• CD11b expression was significantly upregulated on both CD4+ and CD8+ T cells upon stimulation, reaching up to 28% in peripheral T cells and 90% in T cell lines.
• The majority of CD11b+ T cells also expressed CD56.
• Inhibition of CR3 function using antibodies or ligands suppressed anti-CD3-induced T cell proliferation and IL-2 release, whereas CR3-negative T cell lines were unaffected.

Conclusions:

• T cell expression of CR3 is activation-dependent.
• CR3 plays a regulatory role in T cell proliferation and IL-2 production, highlighting its functional significance in T cell responses.