Studies on equine immunoglobulins. I. The antigenic structure of horse IgG, its fragments and subunits.

The paper is a scientific study on the characteristics of the immunoglobulins (specifically IgG) in horses. It uncovers and discusses the five distinct antigenic specificities related to these immunoglobulins.

Equine Immunoglobulin analysis

• The study uses Immunodiffusion analysis; a technique used to analyze the antigenic structure of horse IgG-globulins via their reaction with certain antibodies produced in rabbits against horse IgG.
• Through this filtration technique, five antigenic specificities associated with these equine antigens were identified: Fc1, Fc2, L, Lsp, and Fabsp.

Antigenic Specificity of IgG, its fragments, and subunits

• The study reports that reactivity with anti-Fc1 is shown by both F′c and Fc fragments, while only Fc fragment depicts reactivity to anti-Fc2.
• The absorption of anti-Fab serum with an L chain Fc fragment provides a reagent (anti-Fabsp) that precipitates specifically with Fab fragment,IgG-globulin, or reduced and alkylated IgG.
• Upon exposure to detergent, the treated horse IgG becomes unresponsive to anti-Fabsp, but its reactivity with anti-L or anti-Fc reagents remains constant. However, its reactivity is restorable post the removal of detergent.

Specificities of Horse L chain

• The antisera (blood serum containing antibodies) to horse L chain showed two types of specificities. One is anti-L which is directed against L chain factors of IgG and Fab fragment.
• The other type of specificity is termed anti-Lsp and is directed against determinants present on purified, reduced, and alkylated horse L chains. Anti-Lsp does not react with either native IgG or Fab fragment but does react with free L chains, and IgG-globulins that have been treated with urea, detergent, or heat.