Susceptibility of “Hybrid” Fibrins to Streptococcus Fibrinolysins. ∗

Abstract

Tillett and Garner 1 found that both of the human-rabbit heterologous fibrinogen-thrombin complexes are liquefied by the specific antihuman fibrinolysin formed or secreted by certain strains of S. hemolyticus, native rabbit fibrin being refractory to this specific bacterial lysin.

Quantitative differences, however, are demonstrable between the susceptibilities of the 2 Tillett-Garner hybrid fibrins. Fibrin formed by coagulating human-fibrinogen with rabbit-thrombin, for example, may require a 1:48 concentration of a given streptococcus filtrate to show demonstrable lysis. One-and-a-half times this lytic dose, or a 1:32 concentration, may be required for a similar lysis of fibrin formed by coagulating rabbit-fibrinogen with human-thrombin. Since native human fibrin is dissolved by a 1:64 concentration of this filtrate, the relative susceptibilities of the 2 Tillett-Garner hybrid fibrins may be expressed as 75% and 50% of that of normal human fibrin.

Adopting this same percentage method of recording our experimental data, the relative susceptibilities of about 100 other hybrid fibrins are summarized in Table I.

From this table it is seen that both human-fibrinogen and human-thrombin are carriers of the normal human susceptibility to the Tillett-Garner streptococcus fibrinolysin. With certain human-veterinary hybrid fibrins an almost complete loss of the human susceptibility is noted. Both rhesus-fibrinogen and rhesus-thrombin are approximately 10% human in streptolytic susceptibility.

With the discovery 2 that certain veterinary streptococci are specifically lytic for lower animal fibrins, the above hybrid fibrins were retested with 2 antiveterinary fibrinolyses. Data thus obtained are recorded in Table II.

In these tests, also, both the fibrinogen and thrombin of the susceptible animals (horse, swine) are species-specific in their relationships to streptofibrinolysins. There is here, also, an apparent denaturation of the susceptible component in certain hybrid fibrins. Three hybrid fibrins show fibrinolytic hypersusceptibility.