Antibody activities of immunoglobulins in anti-leptospiral horse sera.

Antileptospiral sera from hyperimmunized horses were fractionated by gel filtration on Sephadex G-200 or by starch block electrophoresis. The fractions were examined quantitatively for leptospiricidal, agglutinating and complement fixing activities. The leptospiricidal activity was higher in the 78 globulin fraction than in the 19S globulin fraction, while the agglutinating activity was shared by both the fractions being higher in the 19S fraction. Complement fixing activity was found evenly in both the fractions. Leptospiricidal and complement fixing activities were higher in gamma-globulin than in T-globulin, while the agglutinating activity was comparable in the two globulin fractions. That is, the agglutinating activity may not always behave along with the leptospiricidal activity. The results were discussed in connection with the therapeutic antiserum product for human use.