On the influence of the reaction,and of desiccation,upon opsonins

The non-specific antiopsonic property of certain neutral salts and of lactic acid has been studied by Hektoen and his co-laborers, but the relation of the reaction to the opsonic activity of serum has so far escaped attention. The results of my experiments show that opsonins are most active in neutral reaction. For this the serums of the dog, ox, pig and rabbit were employed. Lacmoid was used as an indicator. The technic was essentially the same as Wright's. Human leucocytes and staphylococcus aureus were used and the time of incubation was thirty minutes, at 37°C. An alkalinity of the fluid exceeding 1/20 normal KOH prevented the occurrence of opsonization. An acidity of 1/30 normal HCl was sufficient to stop the opsonic function of the serum. Neutralization of the excessive alkalinity or acidity caused reappearance of opsonic activity. On the other hand, an alkalinity or an acidity approaching that of the normal alkali or acid produced a condition of irreversibility of the inactivation. The opsonic index estimated in the usual alkaline reaction of normal serum is far lower than that in a neutral medium.

The high stability of opsonins against desiccation and the high thermostability of dried opsonins are very striking. Almost no reduction of opsonic strength is experienced after a serum is completely dried at 23°C. within a few hours. In dry state opsonins are well preserved even after two years. Dried serums of crotalus, ox and horse gave positive results in this regard. The temperatures of 100°, 120°, 135° and 150° I do not destroy opsonins in the dry state. At 150°C. the serum becomes difficult to dissolve, but opsonins may still be detected in it.