Antibodies recognizing CD24 LAP epitope on human T cells enhance CD28 and IL-2 T cell proliferation

Area of Science:

• Immunology
• Molecular Biology
• Cell Biology

Background:

• Membrane expression of CD24 on activated T lymphocytes requires further elucidation.
• Previous studies noted intracellular and cell-surface CD24 sialic acid-dependent epitopes on activated peripheral blood mononuclear cells, but not the core protein on human T cells.

Purpose of the Study:

• To investigate the expression and function of CD24, specifically its sialic and leucine-alanine-proline (LAP) epitopes, in human T cell subsets.
• To determine the role of CD24 LAP epitopes in T cell activation and proliferation.

Main Methods:

• Analysis of anti-CD24 monoclonal antibody binding to sialic and LAP epitopes on resting and activated normal T lymphocytes.
• Assessment of CD24 epitope expression in interleukin-2 dependent cultures.
• Evaluation of the effect of anti-LAP antibodies on T cell responses to anti-CD3/CD28 stimulation and recombinant IL-2.

Main Results:

• Both CD24 LAP and sialic epitopes were detected on activated CD4+ and CD8+ T cells.
• CD24 sialic epitopes showed stable expression in IL-2 cultures, while LAP epitope expression was transient.
• Anti-LAP antibodies significantly enhanced T cell proliferation in response to anti-CD3/CD28 stimulation and IL-2.

Conclusions:

• CD24, particularly the LAP epitope, is expressed on activated human T cells and plays a role in modulating T cell responses.
• The transient expression of the CD24 LAP epitope suggests a dynamic regulatory function.
• Similarities between human CD24 LAP and murine heat-stable antigen suggest CD24 may act as a signaling molecule in human T cells.