Modulation of antigen-induced T cell proliferation by alpha 2M-trypsin complexes

Area of Science:

• Immunology
• Biochemistry

Background:

• Alpha 2-macroglobulin (alpha 2M) is a major plasma proteinase inhibitor.
• Proteinase-alpha 2M complexes can modulate immune cell functions.

Purpose of the Study:

• To investigate the effect of proteinase-complexed alpha 2M on T cell proliferation.
• To elucidate the mechanism of interference in antigen-induced monocyte-T cell interactions (MTI).

Main Methods:

• Addition of alpha 2M-trypsin (alpha 2M X T) complexes to T cell and autologous monocyte cultures.
• Assessing T cell proliferation and monocyte antigen-presenting capacity.
• Using aprotinin to inhibit the enzyme activity within the complex.

Main Results:

• Alpha 2M X T dose-dependently inhibited T cell proliferation (up to 91%) without affecting free alpha 2M.
• Aprotinin reversed the inhibitory effect, indicating residual enzyme activity is responsible.
• Alpha 2M X T did not impair monocyte HLA-DR, -DP, -DQ expression or IL-1 release.

Conclusions:

• Proteinase-complexed alpha 2M, specifically alpha 2M X T, inhibits T cell proliferation during MTI.
• The inhibition is linked to the residual enzymatic activity of the complex, likely acting on T cells or their mediators.
• Alpha 2M X T does not appear to directly impair the antigen-presenting function of monocytes.