Leucocyte migration inhibition assay from clotted plasma droplets

Area of Science:

• Immunology
• Cellular Immunology
• Diagnostic Assays

Background:

• Leucocyte migration inhibition factor (LIF) is a key cytokine in cell-mediated immunity.
• Conventional capillary tube methods for LIF assays are established but can be labor-intensive and require significant blood volume.
• Optimizing LIF assay techniques is crucial for accurate immunodiagnostics.

Purpose of the Study:

• To compare the efficacy and practicality of a novel clotted plasma droplet LIF assay against the conventional capillary tube method.
• To evaluate the sensitivity, technical simplicity, and blood requirements of the plasma droplet assay.
• To determine the optimal conditions for performing the plasma droplet LIF assay, including antigen type, serum supplementation, and blood storage.

Main Methods:

• Comparison of a clotted plasma droplet LIF assay with the conventional capillary tube method.
• Assessment of assay sensitivity using both particulate (BCG) and soluble (PPD) antigens.
• Evaluation of different serum supplements (horse, human, foetal calf) in the culture medium.
• Investigation of blood sample stability using defibrinated and EDTA anti-coagulated blood under varying storage times (up to 24 hours).

Main Results:

• The plasma droplet LIF assay demonstrated comparable results to the capillary tube method but with enhanced sensitivity and technical simplicity.
• Reduced blood volume is required for the plasma droplet assay.
• The plasma droplet method is effective with both particulate and soluble antigens when supplemented with horse or human serum; foetal calf serum precluded inhibition with soluble antigens.
• Defibrinated blood yielded clear results and maintained detectable LIF activity for up to 24 hours.
• EDTA anti-coagulated blood was less stable, with decreasing migration inhibition after 3 hours and unsuitability for assays after 24 hours.

Conclusions:

• The clotted plasma droplet LIF assay is a more sensitive, simpler, and blood-sparing alternative to the conventional capillary tube method.
• Successful implementation of the plasma droplet assay requires appropriate serum supplementation and consideration of blood anticoagulant and storage duration.
• This optimized assay holds promise for improved immunodiagnostic applications, particularly with stable sample formats like defibrinated blood.