Mitogenic stimulation of human lymphocytes mediated by a cell surface elastase

Area of Science:

• Immunology
• Molecular Biology
• Biochemistry

Background:

• A 45-kDa protein purified as a T-cell mitogen shares sequence similarity with human monocyte/neutrophil elastase inhibitor (EI).
• EI is a known substrate for elastase, prompting investigation into a potential cell surface elastase-like molecule as a binding protein for the 45-kDa mitogen.

Purpose of the Study:

• To determine if a cell surface elastase-like molecule acts as the binding protein for the 45-kDa mitogen.
• To investigate if this interaction mediates mitogenic signal transduction.

Main Methods:

• Flow cytofluorometry was used to quantify cell surface elastase expression on tumor-infiltrating lymphocytes (TILs).
• Mitogenic stimulation was induced using an anti-elastase antibody, both soluble and covalently linked to latex beads.
• Cell proliferation was measured by [3H]thymidine incorporation.

Main Results:

• TILs stained positively for elastase, with an inverse correlation between surface staining and proliferation.
• Covalently linking the anti-elastase antibody to latex beads induced a >4-fold increase in mitogenic stimulation.
• Soluble anti-elastase antibody did not increase [3H]thymidine incorporation.

Conclusions:

• Data support that clustering of an elastase-like molecule on the lymphocyte surface mediates T-cell mitogenesis.
• The binding protein for the 45-kDa mitogen, a serine protease inhibitor (serpin), appears to be a serine protease-like molecule.
• This suggests a novel mechanism for T-cell activation involving elastase-like molecules.