Increase in the complement-content of fresh blood-serum

Abstract

Very soon after coagulation has occurred in blood withdrawn from the vessels, serum begins to be expressed. The amount, at first small, increases rapidly, and in a few hours, at room temperature, contraction of the clot is practically complete. Some observations made in the course of other work suggested that the composition of the serum first yielded differs from that of the serum expressed later, and a special investigation of the point led to the results recorded in this paper. The serum given off from the clot at varying intervals of time after bleeding was tested for its content in hæmolytic complement. This body was selected for examination, not only because it can conveniently be studied in the test-tube, but also because much greater quantitative accuracy of result can be obtained with it than with, for example, a bactericidal complement. In most of the experiments, the serum of rabbits was tested against the red blood-corpuscles of the ox, and the necessary immune-body was derived from the serum of rabbits immunised by repeated injections of these corpuscles. In some instances other combinations were used, as is stated later, but in every case the red cells used for injection and for examination were fresh, and had been freed from serum by being washed thrice in many times their bulk of isotomic salt solution. The experiments fall into two groups, according as the serum examined was from a normal animal or from an animal that had been previously immunised. 1. Normal Serum. The method adopted was as follows:—A rabbit was treated with injections of ox red blood-corpuscles, and when its serum had reached a sufficiently high titre, its blood was withdrawn and the serum obtained. This was then heated for half an hour at 56° C. to destroy the contained complement, and served as a stock of “immune-body” (by which name I shall refer to it in the rest of this paper). The neck of a normal rabbit having been shaved and sterilised, the large vessels of the neck were cut, and the issuing blood was caught in a sterile flask. As soon as coagulation had occurred, the clot was loosened from the sides of the flask by a sterile glass-rod. At varying intervals of time, samples of the separating serum were taken and rapidly centrifuged to free them from cells, and the supernatant fluid was then tested. Each sample was examined separately as soon as it was obtained, instead of waiting for the last sample and examining them all together. The latter method was used as a control in a few cases, but the interval between the taking of the first and last samples extended over several hours, during which time spontaneous deterioration or other change of the complement might easily occur in the earlier samples. Such a change does, in fact, occur, as will be shown later, and it was necessary to avoid this source of error.