Evidence of Local Protection Against Infection with Type I Pneumococcus. ∗

Abstract

The production of local protection or “local immunity” to micro-organismal infection was first fully described by Wassermann and Citron 1 and interpreted by them as an “Umstimmung” or “retuning” of the local cells. This phenomenon has subsequently been observed but differently explained, especially by Besredka, 2 Gay, 3 and Opie. 4

Bull and McKee 5 and recently Walsh and Cannon 6 demonstrated in rabbits a definite specific resistance of the upper respiratory tract to pneumococcal infection subsequent to specific local intranasal instillation. These observers point out that although the rabbit host seems protected in general, evidences of mouse-protective substances are not demonstrable. Gay and Rhodes, 7 on the other hand, found that only the derm was resistant to the streptococcus following experimental erysipelas whereas infection was produced by other routes of inoculation. Extensive literature in this field is afforded by Pacheco 8 and Gay. 9

We employed both hairy and hairless white mice, and Type I pneumococcus A5-51R obtained through the courtesy of Dr. Kenneth L. Burdon and grown on blood-agar slants. When a saline suspension of the pneumococcus killed with 0.4% formalin was injected intraäbdominally on each of 5 days during a period of one week, the animals then survived for 5 to 6 days subsequent to an intraäbdominal injection of living pneumococci that was fatal to controls over night. In seeking a useful ratio of protecting factors to lethal dose it was found that .05 cc of saline suspension of a 24-hour growth, containing approximately one-half billion microorganisms per cc, killed mice within 24 to 48 hours when injected intraäbdominally, thus representing one minimal lethal dose. A similar dose injected subcutaneously killed in 36 to 72 hours.