Alpha-fetoprotein on human peripheral blood lymphocytes does not block complement-dependent lymphocytotoxicity

Area of Science:

• Immunology
• Hepatology
• Cell Biology

Background:

• Alpha-fetoprotein (AFP) is a protein primarily associated with hepatocellular carcinoma (HCC) and fetal development.
• The interaction of AFP with immune cells, particularly lymphocytes, is not fully understood.
• Understanding AFP's cellular interactions is crucial for comprehending its role in HCC pathogenesis and immune evasion.

Purpose of the Study:

• To investigate the binding of alpha-fetoprotein (AFP) to human peripheral blood lymphocytes.
• To determine the effect of temperature on AFP-lymphocyte interaction.
• To assess whether AFP binding interferes with lymphocyte surface antibody recognition.

Main Methods:

• Direct immunofluorescence assay was employed to detect AFP binding on T and B lymphocytes.
• Lymphocytes were incubated with purified AFP or AFP-positive hepatocellular carcinoma (HCC) sera at different temperatures (4°C and 37°C).
• The effect of AFP binding on the activity of cytotoxic antibodies against HLA determinants was evaluated.

Main Results:

• AFP demonstrated binding to 10-20% of T lymphocytes and 5-10% of B lymphocytes at 4°C.
• At 37°C, membrane-bound AFP was significantly internalized or shed, resulting in positive fluorescence on less than 3% of cells.
• Continuous presence of AFP did not impede the action of cytotoxic antibodies targeting lymphocyte HLA determinants.

Conclusions:

• AFP exhibits temperature-dependent binding to human peripheral blood lymphocytes.
• Lymphocyte surface binding of AFP is transient and susceptible to internalization or shedding at physiological temperatures.
• Hepatocellular carcinoma-derived AFP does not inhibit antibody-mediated cytotoxicity against HLA antigens on lymphocytes.