The occurrence of antipneumococcus substances in the blood serum in lobar pneumonia.

Abstract

With a method 1 previously described for carrying on growthinhibition tests with the pneumococcus, it was shown that a mixture of serum and leucocytes from naturally resistant animals (cats or dogs) was capable of inhibiting the growth of pneumococci in considerable numbers, whereas a serum-leucocyte mixture from a susceptible animal (rabbit) was found to have no such action. It was possible, however, to passively confer growth-inhibitory and pneumoccidal powers on serum-leucocyte mixtures of the latter animal by adding a very small quantity of a homologous antipneumococcus serum. By comparing different immune sera the degree of growth inhibition thus obtained paralleled closely their protective action for mice. In a subsequent investigation on experimental pneumococcus infection, it was found that recovery was invariably accompanied by the development in the serum of the infected animals of immune substances, which could be demonstrated by the occurrence of pneumococcus growth-inhibition when such serum was added to rabbit serum-leucocyte mixtures. On the other hand, the serum of animals dying from the experimental disease failed to show such immune changes at any time during the course of the infection. This led to the present study of the occurrence of these antipneumococcus substances in the blood serum of patients with lobar pneumonia.

The method employed was briefly as folliows: Specimens of patient's serum were obtained from blood taken by vena-puncture on various days o'f the illness, and kept in a refrigerator until used. The several serum samples, inactivated beforehand, were tested by adding progressive dilutions of them to normal rabbit serum-leucocyte mixtures, which were in turn seeded with a constant small number of pneumococci. The strains of pneumococci used were either those isolated from the patient yiekling the test serum or a homologous stock strain.