Horse IgG- and ostrich IgY-F(ab’)₂ groups have different affinities for mice erythrocytes and lymphocytes. Implications for avian immunoglobulin therapeutic usefulness.

This study used high-resolution fluorescence microscopy to observe the interaction of various immunoglobulins from horses and ostriches with mouse cell membranes, finding that ostrich IgY may potentially promote adaptive immunity more than horse IgG, which could affect its therapeutic uses.

Research Methodology

• This study had researchers using delicate and precise fluorescence microscopy to examine the interaction between ostrich immunoglobulin (IgY), horse immunoglobulin (IgG), and the F(ab’)₂ fraction of horse IgG with the plasma membranes of lymphocytes and erythrocytes in mice.
• The immunoglobulins were tagged with fluorescein isothiocyanate (FITC), a fluorescent dye, to allow for their tracking and observation under the microscope.

Findings and Observations

• The researchers observed that there was an interaction between IgY and the lymphocyte plasma membrane, but this did not lead to endocytosis (the process where cells absorb proteins).
• In contrast, less IgG and its F(ab’)₂ fraction seemed to bind to the lymphocytes, and this binding was followed by endocytosis, resulting in a widespread cytoplasmic fluorescence in-most lymphocytes exposed to FITC-IgG or FITC-F(ab’)₂.
• The study found no similar cytoplasmic fluorescence in lymphocytes exposed to FITC-IgY, suggesting that endocytosis did not occur with the ostrich immunoglobulin.
• The team also observed differences in the reactions of erythrocytes (red blood cells) exposed to horse and ostrich immunoglobulins. The erythrocytes became intensely fluorescent for at least five hours when exposed to horse Igs, representing an interaction between the substances. However, the researchers saw no labeling or fluorescence when they exposed the erythrocytes to FITC-IgY.

Implications of the Research

• The findings suggest that ostrich IgY may stimulate adaptive immunity more than horse IgG in mammals, which could have important implications for therapeutic applications.
• The fact that adaptive immunity against IgY could be harmful poses a challenge for its intravenous therapeutic use in humans and other mammals. The body’s immune response might react negatively to IgY, reducing its effectiveness as a therapeutic agent.