Ontogeny of the immune response as a basis of childhood disease

Effect of bacterial immunization on experimental reflux nephropathy

This study was designed to test the hypothesis that young animals with vesicoureteral reflux might be more vulnerable to renal parenchymal infection by bacteria to which they had not been previously exposed. Forty-four crossbred male piglets had surgical induction of vesicoureteral reflux at 2 weeks of age and introduction of urinary tract infection at 6 weeks. They were sacrificed at 12 weeks of age. Between the ages of 2 and 6 weeks, 22 piglets received subcutaneous injections of formalin-killed Escherichia coli in incomplete Freund's adjuvant as described. The remaining 22 piglets received incomplete Freund's adjuvant and vehicle alone. The antibody responses to antigenic challenge were weak to moderate. Immunized animals tended to have less renal scarring and better renal tubular uptake of dimercaptosuccinic acid, in addition to significantly lower serum creatinine values (p less than 0.001) and less mesangial cell proliferation in glomeruli (p = 0.05). We conclude that previous exposure to a specific bacterial strain and bacterial immunization have at least a mild protective effect on the development of reflux nephropathy.

Esophagitis associated with Candida infection in a neonate

A 14-day old infant with stomatitis due to Candida albicans presented with frequent emesis and was found to have esophagitis by barium esophagram. She responded promptly to oral Mycostatin suspension: her emesis subsided and the stomatitis resolved. Repeat esophagram on the seventh day of therapy showed complete resolution of the esophageal mucosal abnormalities. Although Candida stomatitis is common in infants, the incidence and appropriate therapy of Candida esophagitis as a complication in otherwise normal infants are unknown. This patient responded well to frequent therapy with an oral, nonabsorbable antifungal agent.

Degree of antibody-independent activation of the classical complement pathway by K1 Escherichia coli differs with O antigen type and correlates with virulence of meningitis in newborns

A total of 95 K1 Escherichia coli strains of the O (lipopolysaccharide) serotypes O1, O7, or O18 had been analyzed previously for the ability to cause bacteremia after colonizing the gut of newborn rats. In this study, these strains were tested for their resistance to the bactericidal activity of rat serum. All strains that had caused bacteremia in a high percentage of the inoculated rats were able to survive for several hours in 90% adult rat serum. With only a few exceptions, O7:K1 and O18:K1 strains were serum resistant and virulent, whereas O1:K1 strains were serum sensitive and avirulent. Serum sensitivity was due to the classical complement pathway. K1 strains of all three O serotypes were resistant to the alternative complement pathway. O7:K1 and O18:K1 cells were killed efficiently after the classical pathway was triggered by specific antilipopolysaccharide antibodies. However, killing of O1:K1 bacteria by the classical pathway system did not require antibodies. Isolated O1-lipopolysaccharide fixed complement more efficiently than did isolated O7- or O18-lipopolysaccharide, suggesting that the differences in the chemical structure of the O antigens are responsible for the observed differences in complement sensitivity. In combination with epidemiological data, the results indicate that antibody-independent classical pathway activation provides an important defense mechanism for newborns against certain gram-negative infections.

Antigen-specific plaque-forming cell response of human cord blood lymphocytes after in vitro stimulation by T cell-dependent antigens

Mononuclear cells isolated from human cord blood (CBL) of full-term neonates were stimulated in vitro with a dose range of T cell-dependent antigens, i.e. ovalbumin or sheep erythrocytes, and tested for the capacity to mount an antigen-specific plaque-forming cell (PFC) response. Both of the antigens used induced in CBL a PFC response with the same kinetics of PFC formation and of the same magnitude as found in cultures of adult peripheral blood lymphocytes (PBL). However, optimal PFC responses in CBL were obtained at a hundredfold lower concentration of the antigens compared with the optimal antigen doses for the induction of a PFC response in adult PBL. This phenomenon was further investigated with respect to the antigen dose dependency of the activation of neonatal B cells and neonatal regulatory T cells. The induction of a PFC response in CBL at antigen concentrations that were suboptimal for adult PBL showed a correlation with the particular antigen dose requirements for the activation of B cells and T helper cells in neonates. Furthermore, the findings suggest that the decrease of the PFC response in CBL stimulated with supraoptimal doses of antigen was not caused by the induction of unresponsiveness at the B cell level or by interference of pregnancy-associated substances with the PFC response, but was rather the result of the activation of antigen-specific T suppressor cells. Neonatal T suppressor cells were activated at antigen concentrations that generated T helper activity in the adult. Thus, although neonatal B cells possess the intrinsic capacity to mature into antigen-specific PFC, the conditions for effective activation of neonatal T cells regulating the B cell response differ from those for the activation of adult regulatory T cells.

Induction of bacteremia in newborn rats by Escherichia coli K1 is correlated with only certain O (lipopolysaccharide) antigen types

A total of 95 Escherichia coli strains (O1:K1, O7:K1, or O18:K1), obtained from different sources of human infections and from healthy individuals, were analyzed for the ability to cause bacteremia after colonizing the gut of newborn rats. Strains of all three serotypes were able to multiply extensively in the gut after oral inoculation and to translocate (in small numbers) to the mesenteric lymph nodes. With only few exceptions, O7:K1 and O18:K1 strains were able to cause bacteremia, while O1:K1 strains could not. Mixed-infection experiments revealed that the bacteria present in the blood during a case of bacteremia are in most cases the descendants of one cell that has multiplied extraintestinally after translocation to the mesenteric lymph nodes. It appears that virulent O7:K1 and O18:K1, but not avirulent O1:K1, bacteria are able to multiply directly in the bloodstream of the newborn rats. No correlation between virulence and the source of isolation of the different strains was observed. Disease isolates thus do not seem to differ from fecal isolates of the same serotype in special virulence properties. The differences in virulence among different O serotypes of K1 E. coli observed in the rat model were comparable to their relative frequency of isolation from meningitis in newborn children.

Reactivation of Epstein-Barr virus in pregnant women: social factors, and immune competence as determinants of lymphoproliferative diseases-a hypothesis

In normal pregnant women, reactivation of Epstein-Barr virus (EBV) frequently occurs. Cellular immune responses are apparently suppressed, but high titer EBV-specific antibodies of IgG class may compensate. The antibodies cross the placenta and protect the infant against primary infection for many months. Reactivation of EBV in pregnancy and oral excretion of virus by normal pregnant women could be one explanation why young children in large sibships (among families of low social classes) become infected early in life. Infants are likely infected by EBV from their pregnant mothers who shed virus in saliva. Moreover, the natural protection for several months in the perinatal period against Burkitt lymphoma and fatal EBV-induced lymphoproliferative diseases in congenitally immune deficient children is explained. The maturity and immunocompetence of the immune system at the time of primary infection by EBV and the size of the sibship seem to determine whether infectious mononucleosis occurs. Gammaglobulin derived from human cord blood may be a valuable source of viral-specific antibodies for serotherapy in immune deficient patients.

Children of female renal transplant recipients

Results of follow-up of 5 children, aged 4.5-9 years, who were born to kidney transplanted mothers are presented. Various immunological parameters were mainly within normal limits with the possible exception of 1 child who exhibited a granulocytopenia which normalized at about 5 years of age. Three children whose mothers were carriers of HBsAg during and after pregnancy have become antigen carriers and show slightly elevated levels of liver transferases. One child has a cardiac anomaly and signs of slight neurological dysfunction. In other respects the children are well and show normal psychomotor and somatic development. The rather sparse information from the literature regarding this group of children indicates a surprisingly low frequency of severe physical complications.