Development of bactericidal properties against gram-negative organisms in the serum of young animals

THE FORMATION AND PROPERTIES OF POLIOVIRUS-NEUTRALIZING ANTIBODY. IV. NORMAL ANTIBODY AND EARLY IMMUNE ANTIBODY OF RABBIT ORIGIN: A COMPARISON OF BIOLOGICAL AND PHYSICOCHEMICAL PROPERTIES

Rabbit sera were found to possess neutralizing activity (normal antibody) to polioviruses and Coxsackie B viruses. This normal antibody showed high specificity in cross-neutralization and absorption tests. It was associated with heat-stable, mercaptan-sensitive, 19S γ₁-β-macroglobulins, which formed weak complexes with the viral antigen. In rare instances, sera with normal macroglobulin antibody, also contained very low activity which was due to 7S γ₂-globulins. The neutralization of poliovirus by normal 19S γ₁-β-antibody appeared to follow first order kinetics, and the thermodynamic parameters of this reaction were the same as those of serological reactions employing immune antibody. The electrophoretic mobility, sedimentation properties, sensitivity to mercaptan, thermostability, and avidity of normal and early (up to day 3) immune antibodies to poliovirus were similar, but differed in several respects from those of late immune antibodies. Thus, the available evidence suggested, that earlier reported differences between normal and immune antibodies reflected differences between antibodies of diverse physicochemical properties rather than between normal and immune antibodies per se. It is proposed that the normal macroglobulin antibody is associated with an immunological response to repeated stimulation with minute amounts of antigen.

Inhibitory effect of capsular antigen of Vibrio vulnificus on bactericidal activity of human serum

Opaque (Op) and translucent (Tr) colonial variants were isolated from Vibrio vulnificus strains. Op-type variants were more resistant than the isogenic Tr-type variants, but the survival rate of the Op-type variants varied with the strains. Antisera were prepared by immunizing rabbit with whole cells of Op and Tr variants of some strains, in which the difference of the sensitivity between Op and Tr cells was remarkable. Then agglutination tests with their living and heat-killed cells were carried out. The results suggested the presence of capsular antigen in Op cells and its absence in Tr cells, with the exception of the existence of a slight amount of capsular material in Tr variants of strain L-180. The thin capsular layer of Tr cells of strain L-180 was also demonstrated electron microscopically, but the layer was thinner than that of the isogenic Op cells. Results of determination of sugar content in the extracted capsular fraction also showed that Op to Tr transformation was due to loss of capsular antigen of the cells. These results confirmed the morphological studies previously reported which suggested the prevention of host defense system by the capsular material of the vibrio.

The use of gnotobiological models for the studies of immune mechanisms

Germfree (GF) animals are widely used for discrimination of natural mechanisms (genetically determined) from adaptive mechanisms of immunity induced by external antigens. GF rats fed at least for first 5 days after birth with artificial diet LNa, deficient in unsaturated fatty acids, were in contrast to those fed with K 50 diet deeply suppressed in humoral and cellular immune reactivities during their life. GF piglets, deprived from maternal colostrum (CF) as a source of passively transferred maternal antibody, immunized with preformed Ag/Ab complexes (HSA anti HSA) responded according to the composition of complexes (Ab excess, equivalence, Ag excess) by low or high dose tolerance or by secondary response. Similar pictures of response were obtained in groups of presensitized GF-CF piglets by immunization with different doses of antigen. It is concluded that 3 different types of response are the result of Ag/Ab complexes acting or formed on the lymphocyte membrane and exerting stimulatory or down-regulatory signals.

Immunological changes after long-term feeding of germfree piglets with protein isolates and yeast cell walls from Candida utilis as food additives

Germfree piglets were fed a diet supplemented with cell walls and a protein isolate from Candida utilis for 54 days. Besides morphological signs of activation of the lymphoid tissue which occurred primarily in the intestine of piglets which had been fed yeast cell walls, even an increased serum immunoglobulin level could be detected. In sera and intestinal content of piglets fed both with cell walls and isolated protein, specific antibodies capable of agglutinating yeasts were present. Even though a limited number of experimental animals was employed it can be concluded that the yeast material added to the diet elicited an immune response.

Differential complement resistance mediates virulence of Haemophilus influenzae type b

Studies were undertaken to gain insight into the virulence of type b in contrast to the other Haemophilus influenzae capsular types. A relationship was found between the comparative virulence of H. influenzae types in humans and their resistance to the bactericidal effect of antibody-free complement. Type b was most resistant to the bactericidal effect of complement. The other types could be divided into three groups based upon their susceptibility to complement; this grouping was also related to their structural similarities. No association between virulence and either the biotype, source of isolate, in vitro association with peripheral polymorphonuclear leukocytes, or the total amount of capsular polysaccharide was found. However, among the type b strains, higher levels of cell-associated polysaccharide were associated with increased resistance to complement. The relative virulence of the six H. influenzae types in the infant rat model was generally similar to that in humans. After intraperitoneal challenge, type b and type a strains had the lowest 50% effective doses for bacteremia, removed by several logs from the values of the other types. By intranasal challenge, type b strains produced higher rates and levels of bacteremia than did type a strains. High levels of natural bactericidal antibodies to types c and e were found in adult female rats; this finding alone could not account for the differences in virulence among the H. influenzae types in the infant rat model. We propose that the virulence of type b strains is due to their greater resistance to the bactericidal activity of serum complement alone. Resistance to type b disease requires serum antibody to induce the complement-mediated reaction.

Peroral immunization of germfree piglets: appearance of antibody-forming cells and antibodies of different isotypes

Precolostral germfree piglets were perorally immunized with sheep erythrocytes daily, beginning on the 5th day of life. At different intervals the numbers of IgM, IgG and IgA antibody-forming cells were estimated in the spleens, lymph nodes and intestinal mucosa by the haemolytic plaque method. In the beginning of the response IgM antibody-forming cells were detected in intestinal mucosa and mesenteric lymph nodes. IgA plaque-forming cells appeared later and were predominant during the whole period in all organs tested. In all lymphatic organs tested the appearance of IgG antibody-producing cells followed that of IgA plaque-forming cells. The development of immunoglobulins and antibody of different isotypes in intestinal contents and sera was compared with the cellular kinetics found in these young animals after local stimulation.

Environmental origin of natural antibodies to teichoic acid

In an effort to determine the origin of natural antibodies to teichoic acid, rats were fed a sterile liquid diet free of detectable teichoic acid and virtually free of gram-positive bacteria. Both germ-free and conventional Sprague-Dawley rats raised on this diet failed to produce antibodies to polyglycerophosphate, whereas 100% of their counterparts fed the usual teichoic acid-containing diet did produce these antibodies. The intestinal flora was similar in both groups of animals. When the test animals were immunized intraperitoneally or orally with gram-positive bacteria, 100% displayed immunocompetency by producing significant levels of antibody. These results demonstrate the environmental nature of the antigenic stimulus for these antibodies and suggest the importance of food as the major source of stimulation. The experimental model described here furnishes a valuable tool for studies of immunologic responses where a single known specificity and a controlled system would be advantageous.

Variability of the immunological state of germfree colostrum-deprived Minnesota miniature piglets

Minnesota miniature piglets obtained by hysterectomy and deprived of colostrum were examined for the presence of immunoglobulin by immunoelectrophoresis, double-gel diffusion, and radial immunodiffusion techniques with specific anti-immunoglobulin chain sera. A large amount of variability existed between different litters of piglets and between different piglets within the same litter, ranging from no detectable immunoglobulin in the serum to very high immunoglobulin levels approaching that of the adult pig. All known classes of porcine immunoglobulin including immunoglobulin G, immunoglobulin M, and immunoglobulin A could be found in the sera from litters where there was extensive placental damage. This contaminating immunoglobulin was shown to have antibody activity to actinophage MSP-2 even when present in very low concentrations. The low level contamination with immunoglobulin G, which was the most frequently encountered type of contaminant, was demonstrated to be similar to sow immunoglobulin G both antigenically and in its molecular size. The data demonstrates that individual piglets must be tested for immunoglobulin content rather than being assumed to be immunologically "virgin" and emphasizes the need for an intact placenta barrier to obtain piglets free from maternal immunoglobulin and devoid of antigenic stimulation.

Complement-mediated bactericidal system: evidence for a new pathway of complement action

The early components of human complement (C1, C4, and C2) plus certain serum euglobulins will kill pathogenic strains of Shigella sonnei. Serum from patients with hereditary C3 deficiencies and specific antiserums to C3, C5, and C6 were utilized to demonstrate the absence of requirements for late-acting complement components in this unusual bactericidal system.

The in vitro and in vivo effects of carrageenin on humoral and cellular factors of natural resistance

The inhibitory effect of carrageenin, a sulfated algal polygalactose, on humoral factors of natural resistance is discussed. In dependence on dose and time, the influence of non-specific and specific bacteriolysis, on the in vitro and in vivo opsonic activity and on the course of infection was studied.

Influence of the intestinal flora on the development of immune reactions in infants

Breast-fed and artifically fed infants are in contact with the O antigen of Escherichia coli from the first days after birth. From the mother, the infant obtains antibodies against nonpathogenic E. coli strains in low titer, and the infant begins to form its own antibodies during the 2nd month of life. The transition is known to be continuous even though the transferred antibodies could not be differentiated from the infant's own antibodies. Contact with endotoxin caused sensitization which was detected by the skin test at about 2.5 months, and thereafter the skin test data correlated with the presence of serum antibodies against endotoxin. The newborn infant can be colonized with a different E. coli serotype; such an antigenic stimulus evokes the formation of antibodies sooner and at a significantly higher titer than (i) the level of maternal antibodies transferred or (ii) the infant's antibodies normally formed later on against other random E. coli serotypes.