Abstract
An intravenous injection of immune serum causes an abrupt disappearance of the bacteria from the circulating blood of animals having a bacteremia or a septicemia. This is due to an immediate agglutination of the bacteria and to an accumulation of the bacterial clumps in the lungs, liver, spleen, etc. The clumps of bacteria are phagocyted and destroyed mainly by the polymorphonuclear leucocytes which accumulate in the internal organs following an intravenous injection of foreign protein substances. The septicemia or bacteremia does not recur as long as the immune serum is kept in the blood in a sufficient concentration.
These phenomena occur very typically following intravenous administration of specific immune sera in rabbits infected with pneumococci or Shiga dysentery bacilli. If the rabbits are actively immune to these bacteria, the same phenomena follow an intravenous injection of the bacteria. If the immune animals are given sufficient quantities of the bacte ia, death may be caused by intoxication in the absence of a septicemia.
In natural immunity the above described phenomena follow immediately upon an intravenous injection of the bacteria. Rabbits have a comparatively high natural immunity to many bacteria, of which the following have been studied in this respect: typhoid bacilli, colon bacilli, dysentery bacilli of the Flexner group, Staphylococcus aureus and albus, non-virulent bacilli of the mucosus capsulatus group, and non-virulent influenza bacilli. All of these are agglutinated, phagocyted, and destroyed in normal rabbits as pneumococci are in immune rabbits and none of them causes a true septicemia in these animals.
Rabbits exhibit little or no resistance towards a virulent strain of Bacillus avisepticus while dogs are not affected by a subtoxic dose. These bacteria are not agglutinated in the circulation of rabbits and soon begin to multiply and produce a fatal septicemia.
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