Abstract
It has long been known that virulent strains of pneumococci or other bacteria are not readily ingested by leucocytes and that avirulent strains are generally ingested readily. It has also been established that the presence of acids, alkalies, salts and other reagents modify the velocity or the extensiveness of phagocytic reactions.
In studies on the parallel relations between virulence, electro-phoretic potential difference (P. D.), agglutinability and other characteristics of bacteria, strains of pneumococci of different virulence for white mice were examined in considerable detail. 1 The pneumococci designated A are virulent Type I organisms. The strains B and C are variants of A which were derived by Blake and Trask by growing strain A in the presence of specific anti-serum. The minimum fatal doses for white mice are: 0.5 × 10-7 cc. for A; 0.5 × 10-3 cc. for B; and 0.5+ cc. for C. The P. D. is highest on A and lowest on C.
The experiments reported here were undertaken to determine the extent to which A, B and C strains of pneumococci are taken up by phagocytes under conditions which were designed to decrease or increase the P. D. It has been established 1 that the virulence for white mice is altered in a parallel manner when the P. D. is increased or decreased.
It has been found that in the presence of normal rabbit serum or of immune horse serum, the sequence of decreasing phagocytic indices is: C, R, A. For the opsonic indices, the series is: A = E > C. The enhancement of phagocytosis by the presence of inheated or heated immune serum is approximately proportional to the concentration of the serum.
It has been found' that the sequence of the relative magnitudes of the P. D. values for the A, B and C strains is inverted by frequent washings with water from A > B > C to C > 13 > A. It was found, correspondingly, that the sequence of the phagocytic indices was also inverted.
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