The Action of Ammonia on Complement. The Fourth Component

Abstract

Small quantities of NH3 have a destructive action on complement, removing a factor hitherto unrecorded. This component and the 3 others previously recognized must all be present for complete complement activity. Hemolysis of sensitized red cells only takes place, therefore, in presence of 2 heat-labile protein components and 2 relatively heat-stable components. The 4th factor is relatively heat-stable and is associated with the albumin fraction. Ammonia-inactivated serum can thus be reactivated by addition of heated serum or by heated or unheated albumin fraction. The 4th component is not identical with the 3rd, which is removed by yeast or zymin, for the 2 are associated with different fractions after splitting of complement by dilute acids. Serum inactivated by zymin will reactivate ammonia-inactivated serum. Other alkalis have no similar specific action. Ammonium salts act only when the serum is previously adjusted to alkaline p h, optimums being above P h 8-0 and below p H 10.0. Thus, free NH3 is necessary for the inactivation process. The velocity at 37[degree] is at least 4 times that at 0[degree]. The new component is non-dialyzable and not destroyed by heating at 56[degree] for 1/2 hour, but it is readily destroyed at 66[degree]. It is destroyed by dilute acids and alkalis at 37[degree].