Variations in resistance of red blood cells in sheep

Abstract

In the course of complement fixation work we have noticed that the specimens of blood cells obtained from different sheep under exactly similar conditions occasionally show marked differences in their susceptibility to laking by specific lytic serum. When this was first noticed we were using two sheep as a source of blood, and as the sheep whose cells were more highly resistant was one which had been bled repeatedly and profusely it was natural to attribute the increased resistance of the cells to this.

We determined to investigate this question and also to find out whether the increased resistance was a specific resistance to laking by amboceptor and complement or was a general resistance such as would be shown by an increased resistance to laking by hypotonic salt solution, and also whether the sera of different sheep show similar differences in their tonicity.

Three sheep were used:—

T—an apparently normal young male sheep, newly obtained from the dealer.

F—a sheep which had been kept in the laboratory for six months and had been bled repeatedly and on occasions profusely.

P—a sheep which had been confined for two and one half years, had been bled occasionally and had received immunizing injections of typhoid bacilli for a period of about eighteen months.

F was slightly and P decidedly anemic. The blood of all three was obtained on the same day and the cells were washed with great care to handle the blood of all three animals in precisely similar ways. All three were made up into 5 per cent suspension and tested with diminishing quantities of hemolytic amboceptor (rabbit serum) and a fixed dose of 10 per cent complement (guinea pig) with the following result:

It is seen that the new sheep, T, was the most resistant to laking, the frequently bled sheep, F, almost as resistant, and the typhoid injected sheep, P, least resistant.