The relationship of the streptococcal hemolysin which is recognized on incubation of RBC with streptococcal cells (cell-bound hemolysin, CBH), to RNA hemolysin, a representative of oxygen-stable hemolysin (streptolysin S) has been studied. A number of similarities have been found in the conditions for optimal production of each of these hemolysins, a requirement for cysteine, Mg++, and glucose; maximal production by streptococci in the stationary phase; similar curves of pH-dependence. In both systems, the production of hemolysin was inhibited by certain antibiotics, by ultraviolet irradiation, and by sonic disruption and was absent in the same streptococcal mutant strain. The hemolytic activity of both systems was inhibited by lecithin, trypan blue, and papain. Similarities were also found in relative susceptibilities to the two hemolytic systems of erythrocytes of a number of animal species. These data support a suggestion advanced in an earlier study that a streptococcal hemolytic moiety, which can be induced by, and carried on, a number of diverse agents to comprise the group of oxygen-stable hemolysins, serves, in its original attachment to a component of the streptococcal cell, to produce the hemolytic effect recognized as the cell-bound hemolysin.

In studies of the mechanism of lysis of red blood cells by washed streptococci with hemolytic activity (cell-bound hemolysin, CBH) no components released spontaneously by RBC or streptococci, or by interaction between these cells, could be found to induce the formation of soluble hemolysin by the streptococci. It was also found that separation of RBC from streptococci even by Millipore filter or a very thin layer of agar could prevent their hemolysis. By means of cellulose columns it was possible to separate RBC from streptococci after a short incubation. RBC thus separated from streptococci with which they had been incubated underwent hemolysis on subsequent incubation at 37°C. By varying the period of incubation prior to separation it was possible to demonstrate the transfer of increasing amounts of hemolysin from streptococci to RBC with increasing periods of incubation. A considerable part of this appeared to be at a constant rate. A theory is presented on the relationship between the streptococcal cell-bound hemolysin and the group of oxygen-stable streptococcal hemolysins, in terms of a transferable hemolytic moiety and binding sites for this moiety on the streptococcal cell, on various molecular species which can act as inducers of the oxygen-stable hemolysins, and on the RBC, with the affinity of the respective binding sites for the hemolytic moiety increasing in that order.