THE DISTRIBUTION IN THE BLOOD AND LYMPH OF PNEUMOCOCCUS TYPE III INJECTED INTRAVENOUSLY IN RABBITS, AND THE EFFECT OF TREATMENT WITH SPECIFIC ANTISERUM ON THE INFECTION OF THE LYMPH

Experiments are described which show that in rabbits infected intravenously with virulent Type III pneumococci, these organisms are found not only in the thoracic duct lymph, as previously reported, but also in lymph from the cervical and leg lymphatics. The nonmotile bacteria must have crossed both vascular and lymphatic endothelium in reaching the lymph. Intracellular transportation by phagocytes is apparently not the means by which this is effected. The intravenous and intraperitoneal injection of large amounts of homologous type-specific antibody fails even after many hours to terminate or permanently reduce the pneumococcal infection of the lymph. The failure of antiserum to sterilize the lymph is discussed.

THE PASSAGE OF TYPE III RABBIT VIRULENT PNEUMOCOCCI FROM THE VASCULAR SYSTEM INTO JOINTS AND CERTAIN OTHER BODY CAVITIES

1. Within 24 hours following intravenous inoculation with rabbit virulent strains of pneumococcus Type III, most rabbits develop infections of one or both knees. The frequency of bilateral knee joint involvement increases as the duration of the disease is prolonged. 2. The spinal fluid, aqueous humor, and bladder urine remain sterile at a time when the knee joints contain pneumococci. Subsequently, however, they may be invaded. 3. The administration of a single dose of type specific horse immune serum, at a period when in all probability one or both knee joints contain organisms, appears to be ineffective in bringing about resolution of the infections process in these sites, even though horse serum constituents may be demonstrated serologically to be present within the joint cavities.

STUDIES ON NATURAL IMMUNITY TO PNEUMOCOCCUS TYPE III : IV. OBSERVATIONS ON A NON-TYPE SPECIFIC HUMORAL FACTOR INVOLVED IN RESISTANCE TO PNEUMOCOCCUS TYPE III

Since there is no evidence for the occurrence of type specific antibody in the normal rabbit and since, as we have shown, the Pneumococcus Type III whether avirulent or virulent is not removed from the blood stream or destroyed when the capsule is intact, the following factors which have been revealed in the course of our work appear to represent certain essential components, if not the complete mechanism, upon which the natural immunity of the rabbit against this organism depends. (a) The elevation of the body temperature after intravenous infection to 41°C. or thereabouts and its maintenance for varying periods. (b) The ability of the phagocytic cells, both fixed and mobile, to attack any cocci which have become vulnerable through the deterioration of capsular integrity. (c) The adjuvant effect of an antibody, reacting with the somatic C carbohydrate, which enhances the phagocytosis of such organisms as no longer possess a completely intact envelope. Conversely, the varying degrees of virulence for rabbits observed among Pneumococcus Type III strains are based upon: (a) differences in the ability of the organisms to multiply at the elevated temperatures encountered in the infected host. Strains markedly susceptible to the harmful influence of this factor fail to induce a generalized fatal infection. Not all "thermo-resistant" strains are highly virulent, however, and these may contrast sharply with regard to (b) size of the capsule and the ease with which it is impaired or completely lost. The capsules must be maintained intact for a sufficient time until multiplication of the organisms can proceed to such a degree that death of the host results. Avirulent strains even when capable of growth at 41°C. appear to be unable to satisfy this requirement. The differences in virulence of various strains apparently conditioned by these factors are not limited solely to the case of the rabbit, since for at least two strains similar differences in virulence have been shown to exist when the intravenous route of infection is employed in mice.

THE PASSAGE OF PROTEINS FROM THE VASCULAR SYSTEM INTO JOINTS AND CERTAIN OTHER BODY CAVITIES

1. Experiments designed to study, in the rabbit, the passage of foreign proteins from the blood stream into synovial fluid and to compare such passage with that taking place into the aqueous humor, spinal fluid, and urine are described. 2. Crystalline egg albumin and horse serum proteins regularly appeared in the knee joints within short periods of time following their intravenous injection. 3. These proteins also appeared promptly in the aqueous humor but in lower concentrations. In the spinal fluid they appeared only rarely and in minimal amounts. 4. Crystalline egg albumin was readily eliminated from the body via the urine. It was also removed rapidly from the knee joint and anterior chamber of the eye. 5. Horse serum proteins appeared only occasionally in the urine. Their concentration in the blood serum remained relatively high for several days. Their increased concentration in the joint fluids in the longer experiments indicates that the rate of entrance exceeded the rate of removal. 6. Foreign proteins of the type employed were all found in the joint fluids in higher concentrations than they were in the other body fluids examined. 7. The possible significance of this study with respect to normal joint physiology and to certain abnormal joint conditions has been commented upon.

THE EMIGRATION OF PNEUMOCOCCI TYPE III FROM THE BLOOD INTO THE THORACIC DUCT LYMPH OF RABBITS, AND THE SURVIVAL OF THESE ORGANISMS IN THE LYMPH FOLLOWING INTRAVENOUS INJECTION OF SPECIFIC ANTISERUM

1. Rabbits injected intravenously with a large dose of a virulent Type III Pneumococcus develop a bacteremia, and within an hour organisms may be cultivated from the thoracic duct lymph. The rapidity with which entrance into the lymph occurs appears to be correlated with the size of the dose injected. 2. The organisms may become more numerous in the lymph than in the blood. 3. If homologous or heterologous antisera are injected, the blood may be sterilized, but though the organisms may be lessened in the lymph, sterilization at least within 4 hours is not secured, and in the intact animal living organisms must continue to enter the blood with the thoracic duct lymph. 4. In infected rabbits after intravenous injection of considerable quantities of antisera containing moderate amounts of agglutinin, no antibody appears in the thoracic duct lymph although the presence of horse serum may be detected. The injection of a very large quantity of antiserum containing a high titre of agglutinin is followed by the penetration of antibody into the lymph. This, however, has failed to sterilize the lymph or to permanently affect the rate of multiplication of the pneumococci.

STUDIES ON NATURAL IMMUNITY TO PNEUMOCOCCUS TYPE III : I. THE CAPACITY OF STRAINS OF PNEUMOCOCCUS TYPE III TO GROW AT 41 degrees C. AND THEIR VIRULENCE FOR RABBITS

1. A correlation appears to exist between the failure of certain strains of Pneumococcus Type III to grow at 41°C. and their lack of virulence for rabbits. 2. It is likely that the capacity to grow at 41°C.—an attribute constantly but not exclusively associated with strains of Pneumococcus Type III virulent for rabbits—is a prerequisite, but not the sole factor, in determining their virulence for these animals.

STUDIES ON NATURAL IMMUNITY TO PNEUMOCOCCUS TYPE III : II. CERTAIN DISTINGUISHING PROPERTIES OF TWO STRAINS OF PNEUMOCOCCUS TYPE III VARYING IN THEIR VIRULENCE FOR RABBITS, AND THE REAPPEARANCE OF THESE PROPERTIES FOLLOWING R-->S RECONVERSION OF THEIR RESPECTIVE ROUGH DERIVATIVES

The results which have been presented show that under the conditions of artificial cultivation at 37°C. definite differences exist between two smooth strains of Pneumococcus Type III both of which are highly virulent for mice by the intraperitoneal route, but which may be sharply distinguished in their virulence for rabbits. These differences consist in the size of the fully developed intact capsule and the interval of time required for its loss. The somewhat smaller capsule of the avirulent strain, well formed and easily demonstrable during the early period of growth, diminishes quickly, while the large capsule of the strain virulent for rabbits is retained for a considerably longer period. Closely correlated with the time at which this reduction of capsule occurs is the appearance of changes in the surface properties of the bacteria which are revealed by a shifting of the range of acid agglutination, susceptibility to clumping in anti-R serum and ingestion by normal adult human polymorphonuclear leucocytes and serum. Since it has been shown that these alterations as growth continues, result in a loss of characteristics which distinguish the strictly type specific, fully capsulated pneumococcus and ultimately lead to a state temporarily approximating that of the completely avirulent R form, and since under the experimental conditions they are inaugurated sooner, advance more rapidly and are more complete in the rabbit avirulent organism, we believe that they may partly account for difference in rabbit virulence of the two strains. In the following paper an attempt has therefore been made to correlate this behavior in vitro with the events attendant upon inoculation into the animal body. The studies of Clark and Ruehl (16), Henrici (17), Bayne-Jones and Adolph (18) and others have demonstrated a marked increase in the size of the bacterial cell associated with the early phases of growth. These authors have dealt chiefly with noncapsulated rod forms and even Clark and Ruehl who included cultures of various cocci do not make reference to variations in capsule size. Recently Seastone (19) has called attention to the large volume occupied by young capsulated streptococci. Similarly we have found that increase and decrease of Pneumococcus Type III volume appears to be due largely to the formation of capsule in young cultures and its subsequent loss as the organisms age. Because of the relatively great proportion of capsule in comparison with soma, a greater disparity exists between the volume of young and old pneumococci than that found by those who have studied bacteria lacking this structure. Of interest in connection with our observations are those of Preisz (20) on the nature of the capsules of virulent anthrax bacilli and strains attenuated by cultivation at 42.5°C. The latter produced soft, rapidly dissolving capsules while such structures in the former were characteristically firm and were retained by the bacilli for longer periods. This worker also noted in confirmation of the earlier work of others, that the capsules of B. anthracis are lost during the course of growth in serum media and in the subcutaneous tissues of the susceptible mouse. We have demonstrated that the R variants derived under the same conditions from the two smooth strains of Pneumococcus Type III reveal certain characteristics by which they may be distinguished from each other in respect to cell and colony morphology, growth in broth, as well as growth at 41°C. (cf. Paper I). By employing the method of Griffith, these two R variants have been induced to revert to the S form. Following the injection into mice of the various possible combinations of living R variant and the killed S organisms of either rabbit virulent or avirulent strain, as well as very large numbers of the R variant alone, S forms emerged which in their various attributes, notably that of virulence for rabbits, resembled the original smooth strain from which the particular R variant involved was dissociated. The function of the smooth killed organisms in the process of transformation appeared to be only that of a stimulus toward reversion to the S. They apparently play no rôle in determining the virulence or the growth properties of the resulting S form. These observations indicate that the factors involved in virulence are conditioned by stable physiological properties peculiar to the individual strain and that although temporarily inactive during the R state, they are again resumed unaltered upon the transition to the S form. They serve also to reemphasize the fact, apparent from several studies but perhaps not sufficiently realized, that the R variants of the pneumococcus, even though obtained under the same conditions from the same type but from different strains, may vary definitely in their various attributes. Finally, they strongly suggest that the degree of virulence of a given strain of a bacterial species may be determined not only by its ability to multiply in the environment of the host and to synthesize certain substances of definite chemical and antigenic properties, but also by the capacity to elaborate these in greater or lesser degree and under the conditions of parasitism within the animal body to maintain them in contact with the soma of the cell in such state that they afford an efficient barrier to the defensive mechanisms of the host.

STUDIES ON NATURAL IMMUNITY TO PNEUMOCOCCUS TYPE III : III. CORRELATION OF THE BEHAVIOR IN VIVO OF PNEUMOCOCCI TYPE III VARYING IN THEIR VIRULENCE FOR RABBITS WITH CERTAIN DIFFERENCES OBSERVED IN VITRO

AMONG THE EXPERIMENTAL FINDINGS REPORTED IN THIS PAPER TO WHICH WE WISH TO GIVE PARTICULAR EMPHASIS ARE THE FOLLOWING: 1. The results which follow the intravenous injection into rabbits of two strains of Pneumococcus Type III of different degrees of virulence vary with the state of the capsule. Thus when this structure is completely developed both remain in the blood. A culture of either strain begins to become susceptible to the blood-clearing mechanism contemporaneously with the onset of capsular degeneration and the initiation of other concomitant changes at the surface of the organism (cf Paper II), which occur much earlier with the less virulent strain. 2. When, in either case, removal from the blood stream occurs, this is effected by the phagocytic cells of the body. There is no suggestion that a new or unknown mechanism is involved. The greatest share of the burden is borne by the fixed phagocytic cells of the liver and spleen, and to a less extent by those of the lung and bone marrow. Nevertheless, it has been demonstrated that the polymorphonuclear leucocytes may also participate. 3. Phagocytosis by the leucocytes of the normal animal either in intro or in vivo has been observed only at such a time as the capsule has become impaired. Ingestion of the organisms by the fixed tissue cells appears also to be effective only under the same condition and is accordingly observed with much younger cultures of the less virulent strain. 4. Following their removal from the blood and their accumulation within the fixed phagocytes of the organs, destruction of most of the cocci proceeds within 2 to 4 hours. Both strains are destroyed provided they are in the state favorable to phagocytic attack. 5. Evidence has been presented which indicates that just as in vitro, so in a local area of inflammation within the body, aging with attendant capsular loss and increasing susceptibility to phagocytosis may take place. 6. With organisms from either strain a variable period of lag follows their injection into the blood stream, even when they are introduced in a state of active multiplication and complete encapsulation. 7. Differences in virulence for rabbits of two strains of Pneumococcus Type III do not imply that this animal possesses a defensive mechanism which is absent in other species, since it has been possible to demonstrate similar differences when the organisms are injected intravenously into mice. This fact indicates that the factors determining the degree of virulence of these strains are to be sought in the organisms themselves, rather than in the kind of host.

Susceptibility of chicks to experimental infections with Neisseria gonorrhoeae

Chicks were given intracerebral inoculations of Neisseria gonorrhoeae of colony types 1 or 2 one to two days after hatching. Small numbers ofN. gonorrhoeae initiated lethal infection provided that the body temperature of the animals was not maintained at levels harmful to the microbes per se. The disease process, which appeared to be localized intracranially rather than disseminated by bacteremia, merits further investigation as a model for the study of pathogenetic and immunologic mechanisms in gonococcal infection.