A crude filtrate from a culture of Clostridium perfringens, type A, was fractionated by a heavy metal-alcohol technique, and some degree of concentration of biologically active factors was achieved. Both the crude material and the fractions obtained were characterized in terms of their alpha toxin, theta toxin, hyaluronidase, and collagenase activities.

The filtrate and fractions were tested for their effect on the peripheral circulation of the rat, using the epinephrine threshold technique. The crude material and several fractions caused a sharp increase in epinephrine sensitivity of the capillary bed of the meso-appendix of the rat; fraction R3B1 giving an 86-fold increase in sensitivity. This reaction could be inhibited by specific antitoxic serums but not by normal serum. The "circulation factor" was shown to be heat-labile and appears to be independent of either the alpha or theta toxins. Bilateral nephrectomy greatly reduced, but did not abolish, the effect of the toxin, while the threshold response to epinephrine was not materially changed following bilateral adrenalectomy.

The crude filtrate and several fractions were shown to inhibit the phagocytosis of heat-killed B. anthracis to the extent of 40 to 50 per cent. Fraction R3C2 was devoid of all biological properties studied here, except phagocytosis inhibition, suggesting that the factor responsible for this activity is distinct from the "classical" toxins and the "circulation factor." Moreover, a 1:5000 dilution of an antiserum prepared against this fraction would completely neutralize the phagocytosis inhibition factor but failed to inhibit any of the other toxic activities.

Since cardiovascular collapse and absence of phagocytosis are two significant clinical findings in gas gangrene, the possible roles of the "circulation" and "phagocytosis inhibition" factors in the pathogenesis of this disease are discussed.

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