Affinity and distribution of subpopulations of antibody-producing cells in protein-restricted C57BL/6 mice.

To study the effect of protein restriction on the affinity of antibodies produced by plaque-forming cells (PFC), C57BL/6 mice were fed diets containing 4% (R4%), 8% (R8%), or 27% (N) casein for 2 (short-term) or 12 (long-term) weeks and immunized with dinitrophenyl (DNP) bovine gamma-globulin in complete Freund's adjuvant. Affinity was assessed by inhibition of plaque formation in the presence of free hapten. Anti-DNP PFC per 10(7) spleen cells were not diminished in short- and long-term R8% mice, and were increased in the former group at certain times after immunization. Affinity of indirect PFC was increased at Days 14 and 21 after immunization in short-term R8% mice and at Day 7 in R4% mice, and was similar in long-term R8% and N animals. No limitation in the heterogeneity of PFC affinities was observed in the restricted groups. Short-term restricted mice showed a rise of the high-affinity PFC subpopulation. The number of mice with hapten-augmentable PFC was diminished in the short-term R8% group at 7 days after immunization and in long-term restricted mice at 14 days, suggesting depressed levels of auto-anti-idiotypic antibodies in protein restriction.

Polyclonal B-cell response to stimulation with Escherichia coli lipopolysaccharide in dietary protein restriction.

The polyclonal B-cell response to Escherichia coli lipopolysaccharide was studied in C57BL/6 mice maintained after weaning on either a moderate protein-restricted diet with 8% casein or a normal diet. After in vitro or in vivo stimulation with the endotoxin, autoreactive and anti-hapten antibody-producing cells were quantitated by direct plaque assay, using bromelain-treated mouse erythrocytes and trinitrophenylated sheep erythrocytes as targets. Larger numbers of plaque-forming cells were generated in cultures of spleen cells from dietary-restricted than from normal mice stimulated with various doses of lipopolysaccharide. The number of background plaque-forming cells was also higher in nonstimulated spleen cell cultures from restricted animals. After injection of lipopolysaccharide in vivo, the number of cells producing antibodies to bromelain-treated mouse erythrocytes per 10(7) spleen cells was significantly increased in dietary-deficient mice. The results are discussed in relation to the different sensitivities of lymphocyte populations to protein deficiency and to the possible presence of high levels of endogenous polyclonal B-cell activators in the restricted mice.

Enhancement of the in vitro antibody response in dietary protein restriction. Failure in the regulation of antibody synthesis.

We have studied the antibody response in vitro of spleen cells from C57BL/6 mice kept on a protein deficient (D) or a normal diet (N). Short or long term protein restriction initiated after weaning led to increased plaque forming cell (PFC) responses to sheep red blood cells (SRBC), TNP-ficoll and TNP lipopolysaccharide. The influence of dietary restriction on the suppression of the antibody response to SRBC was studied in mixed cultures of antigen sensitized and fresh, non-immune cells from either D or N donors. Addition of pre-sensitized D or N cells to non-immune N spleen cells in a 1:1000 ratio resulted in marked suppression of the PFC response whereas co-cultures of pre-sensitized cells and non-immune D spleen cells did not result in significant suppression. Similarly, non-immune T cells from DF mice exerted a lower suppressor effect than non-immune T cells from N mice. Either dietary restriction or low dose cyclophosphamide treatment of the donors of non-immune spleen cells determined a similar reduction in suppression. It is suggested that nutritional deficiency selectively depletes short-lived suppressor effector lymphocytes which are activated in the presence of antigen-stimulated inducer cells.

Influence of protein restriction on lymphoid cell populations characterized by the binding of peanut agglutinin.

Cells binding peanut agglutinin (PNA) were studied in the thymus, spleen, and mesenteric lymph nodes from mice placed in the post weaning period on protein-restricted diets containing 8% (R8%) and 4% (R4%) casein. The proportion of PNA+ thymocytes and the absolute number of total and PNA+ cells in the thymus were significantly diminished in R8% and R4% mice. Larger proportion of PNA+ thymocytes showed weaker fluorescence in R8% and R4% than in normally fed (N) animals. Recovery of PNA+ thymocytes was observed in R8% but not in R4% mice at 8 weeks. The number of total and PNA+ cells was significantly diminished although the proportion of PNA+ cells was not modified in the peripheral lymphoid organs of R8% and R4% mice. Results indicate that protein restriction preferentially affected the immature cortical PNA+ cells in the thymus whereas cell depletion in the peripheral lymphoid organs occurred at the expense of both the PNA+ and PNA- subpopulations.

Influence of the oral administration of excess copper on the immune response.

We have studied the influence of the oral administration of excess copper (Cu) on the immune response. With this aim, mice maintained on standard laboratory diet received 50, 100, 200, or 300 ppm of Cu as copper sulfate in the drinking water during 3 to 10 weeks. Inhibition of the proliferative response to concanavalin A was observed in mice exposed to 100 ppm of Cu for 8 weeks and to 200 ppm of Cu for either 3 or 8 weeks. Conversely, a significant increase in the proliferative response to Escherichia coli lipopolysaccharide (LPS) was observed in mice exposed to 50 or 100 ppm of Cu for 3 weeks. However, the response to LPS was also significantly inhibited following prolonged Cu administration. In contrast, mice exposed to low or high Cu doses during short or long periods showed increased production of autoantibodies directed to bromelain-treated mouse erythrocytes. The DTH response to sheep red blood cells was not modified following short-term administration of 100 ppm of Cu, but was depressed after prolonged exposure to this dose of the metal. Significant inhibition of the DTH response was observed in mice exposed to 300 ppm of Cu for 5 or 10 weeks. Thus, oral administration of excess Cu altered the immune response in a fashion related to the dose and duration of treatment.

Calorie restriction modifies the delayed-type hypersensitivity response to the hapten trinitrobenzenesulfonic acid and to hapten-modified syngeneic spleen cells.

We have studied the influence of different degrees of calorie restriction on the induction and the regulation of the delayed type hypersensitivity (DTH) response to trinitrobenzenesulfonic acid (TNBS) and TNBS-modified spleen cells (TNBS-SC), injected by the sc or the iv route. Immediately after weaning, BALB/c mice were placed on restricted diets for either 2 or 4 weeks and then the DTH response was induced. The results showed that a 37.5% restriction in the food supply significantly depressed the level of the DTH response induced by the sc injection of TNBS-SC. In contrast, a 25% restriction in the food supply was insufficient to depress the response. Calorie restriction did not modify the inhibitory influence of an iv injection of TNBS-SC on the DTH response. However, iv presensitization with free hapten or the simultaneous injection of TNBS-SC by the iv and the sc routes did not significantly depress the DTH response in calorie-restricted mice, indicating a defect in the inhibitory regulation of the DTH response in these dietary groups.

Mitogenic effect of zinc on lymphocytes from strains of mice that are either high or low-responder to T-cell mitogens.

We have studied the in vitro mitogenic effect of ZnCl2 in cultures of lymphocytes from Balb/c or C57BL/6 mice which are high-responder or low-responder to T-cell mitogens respectively. Zn induced proliferation of spleen cells from Balb/c mice cultured without 2-ME. Higher levels of proliferation were observed in cultures with 2-ME. In contrast, Zn only induced proliferation of spleen cells from C57BL/6 mice in the presence of 2-ME. No response to Zn was observed in cultures without 2-ME, of spleen cells from either Balb/c or C57BL/6 mice depleted of plastic adherent cells. However, in cultures with 2-ME, Zn induced proliferation of non-adherent as well as plastic adherent cells from either strain of mice. In cultures without 2-ME, Zn induced proliferation of thymocytes from Balb/c mice, whereas did not show constant mitogenic effect on thymocytes from C57BL/6 mice. In contrast, Zn determined higher levels of proliferation of thymocytes from either strain of mice when cultured with 2-ME. Zn had earlier and stronger mitogenic effect on mature thymocytes of either strain of mice than in total thymocytes, both in cultures with or without 2-ME. However, Zn did not induced proliferation in cultures of immature thymocytes of either strain of mice.

Influence of dietary protein restriction on the delayed-type hypersensitivity response to sheep red blood cells in mice.

Delayed-type hypersensitivity responses to sheep erythrocytes were studied in inbred C57BL/6 and outbred NMRI mice fed either protein-deficient diets containing 8% and 4% casein or a normal diet with 27% casein. Following sensitization with optimal doses of antigen, the magnitude of the response was similar in mice fed the 8% protein and the normal diet. Large numbers of sheep red blood cells which suppressed the delayed hypersensitivity response in normal mice, failed to inhibit this response in animals fed the 8% casein diet. However, the titres of serum haemagglutinins were similar in mice of either dietary group immunized with high doses of antigen. Sensitized spleen cells from deficient mice kept on the 8% casein diet, had lower suppressor capacity than those from normal mice upon transfer into syngeneic hosts. Delayed-type hypersensitivity was significantly depressed in mice fed the 4% protein diet whereas the titres of serum antibodies to sheep erythrocytes were not diminished.

Nonspecific immunodepression and protective immunity in mice infected with Leishmania mexicana.

C57BL/6 mice infected with Leishmania mexicana showed depression of the in vitro immunoglobulin M-plaque-forming cell response to sheep erythrocytes. Immunodepression was present 3 weeks after inoculation and was maximal at 11 weeks. Thereafter, there was a gradual return to normal immunoresponsiveness correlated with the resolution of lesions. At the time of maximal immunodepression, spleen cells from infected mice diminished the plaque-forming cell response to sheep erythrocytes of normal spleen cells. On the other hand, specific responses, as exemplified by protective immunity to a challenge infection and delayed hypersensitivity responses to parasite antigens, were apparently unaffected. These responses were both present in mice bearing primary lesions and were maximal in recovered mice. The significance of these findings is discussed in relation to a current hypothesis on parasite-induced immunodepression.

Zinc administration restores the impaired immune response observed in mice receiving excess copper by oral route.

To study if treatment with zinc (Zn) was able to restore to normal levels the depressed immune response determined by oral administration of excess copper (Cu), groups of mice receiving 100 ppm or 200 ppm of Cu in the drinking water for 8 weeks, were injected ip once a week with Zn (1.14 mg/kg of body weight), throughout the experimental period. Administration of Zn restored to normal levels the proliferative response to mitogens and the antibody response to sheep red blood cells in the group of mice receiving 100 ppm of Cu in the drinking water. Similarly, the treatment with Zn significantly enhanced the depressed proliferative response to mitogens and the antibody response to sheep red blood cells of mice receiving 200 ppm of Cu in the drinking water. By contrast, increment in Zn supply was not able to modify the high production of auto-antibodies observed in animals receiving excess Cu. The results suggest that the impairment of the immune response observed in animals receiving excess Cu could be in part due to antagonistic interactions between this cation and Zn.

Effect of growth phase and parental cell survival in river water on plasmid transfer between Escherichia coli strains.

We evaluated the transfer to and from Escherichia coli of endogenously isolated plasmid material from the River Butrón during the growth of three donor strains and two recipient strains as well as after the survival of these parental cells in river water. Transfer frequency varied greatly during the growth of donor cells, with minimum values in the exponential phase; frequency remained constant, however, during the growth of recipient strains. After survival in river water, donor cells lost their ability for plasmid transfer before any other physiological variations in the cells caused by environmental stress were detected. Under the same conditions and during equal periods, however, no variation in the ability of recipient cells to receive and express plasmid material was observed.

Conjugal transfer of R plasmids to and from Enterobacteriaceae isolated from sewage.

The potential of the transfer of natural plasmids between sewage strains has been studied. In vitro transfer was conducted at 37 degrees C in tryptone soya broth and sterile raw sewage as mating media. In situ transfer was carried out in sterile raw sewage within membrane diffusion chambers at 10.6 degrees C. When the recipient was a laboratory strain of Escherichia coli K-12, the in situ frequency values were significantly lower (P less than 0.001) than those obtained in vitro for the same mating pair. When the laboratory recipient was replaced with recipients from the same sewage source, frequency values decreased progressively from the optimum conditions to the most adverse. However, in situ frequency values were higher than those for the same donors mated with a laboratory recipient.

Inhibitory activity of cranberry juice on adherence of type 1 and type P fimbriated Escherichia coli to eucaryotic cells.

Inhibition of bacterial adherence to bladder cells has been assumed to account for the beneficial action ascribed to cranberry juice and cranberry juice cocktail in the prevention of urinary tract infections (A. E. Sobota, J. Urol. 131:1013-1016, 1984). We have examined the effect of the cocktail and juice on the adherence of Escherichia coli expressing surface lectins of defined sugar specificity to yeasts, tissue culture cells, erythrocytes, and mouse peritoneal macrophages. Cranberry juice cocktail inhibited the adherence of urinary isolates expressing type 1 fimbriae (mannose specific) and P fimbriae [specific for alpha-D-Gal(1----4)-beta-D-Gal] but had no effect on a diarrheal isolate expressing a CFA/I adhesin. The cocktail also inhibited yeast agglutination by purified type 1 fimbriae. The inhibitory activity for type 1 fimbriated E. coli was dialyzable and could be ascribed to the fructose present in the cocktail; this sugar was about 1/10 as active as methyl alpha-D-mannoside in inhibiting the adherence of type 1 fimbriated bacteria. The inhibitory activity for the P fimbriated bacteria was nondialyzable and was detected only after preincubation of the bacteria with the cocktail. Cranberry juice, orange juice, and pineapple juice also inhibited adherence of type 1 fimbriated E. coli, most likely because of their fructose content. However, the two latter juices did not inhibit the P fimbriated bacteria. We conclude that cranberry juice contains at least two inhibitors of lectin-mediated adherence of uropathogens to eucaryotic cells. Further studies are required to establish whether these inhibitors play a role in vivo.

Detection and enumeration of viable but non-culturable transconjugants of Escherichia coli during the survival of recipient cells in river water.

Viable but non-culturable transconjugant cells were detected by a modification of the direct viable count (DVC) method. This modification involved the addition of parental antimicrobial markers (kanamycin and streptomycin) to the elongation medium in order to promote selective elongation of the transconjugant cells. Presence of viable, other than culturable, transconjugants was demonstrated in matings with parental cells from TSB culture as well as with recipient cells from survival in river water (under illuminated and non-illuminated systems). In matings with a recipient strain from illuminated systems, culturable transconjugants were not detected after the third day of recipient cell survival. In spite of this, viable transconjugants were detected in numbers that exceeded 10(5) cells ml-1. These results clearly show that a fraction of non-culturable recipient cells is able to receive and express plasmids by conjugation processes and form viable but non-culturable transconjugant cells.

In vitro antibody synthesis by peripheral blood mononuclear cells from patients with sickle cell disease.

To study the capacity of peripheral blood mononuclear cells (PBMC) from patients with sickle cell disease to synthesize antibodies in vitro, the levels of IgM, IgG, and IgA were quantitated in supernatants of cultured PBMC from a group of asymptomatic adults with sickle cell disease and from normal controls. The rates of spontaneous synthesis of IgM were similar in nonstimulated cultures of PBMC from patients and controls, whereas the amounts of IgG and IgA produced spontaneously by nonstimulated lymphocytes from the patients were significantly greater than those from controls. Similar levels of IgM, IgG, and IgA were detected in the supernatants of cultures stimulated with pokeweed mitogen from patients and controls. Thus, the capacity of PBMC to respond in vitro to pokeweed mitogen was preserved in the patients. The enhanced spontaneous synthesis of IgG and IgA suggests the presence of chronic polyclonal activation of B cells and/or defective regulation of the production of antibodies.

Antibodies to dietary antigen in serum from patients with sickle cell anemia.

The levels of antibodies of the IgG, IgA and IgM isotypes reacting against ovoalbumin (OVA), gliadin (GL) and cow's milk proteins (CMP), were determined by ELISA in sera from a group of adult patients with sickle cell anemia (SCA) bearing homozygous Ss hemoglobinopathy and from matched health donors. Only patients with steady-state disease were included in the study. Increased amounts of IgG and IgA reacting with OVA, GL and CMP were observed in the group of patients as compared with the controls. In contrast, the levels of IgM antibodies against each of the three dietary antigens were similar in patients and controls. Increased levels of IgG and IgA antibodies against dietary antigens in SCA may result from enhanced permeability of the gut mucosa to macromolecules of dietary origin as a consequence of microinfarctions, chronic polyclonal B cell activation and/or diminished inhibitory control of antibody synthesis.

Immunogenetics of atopic asthma: association of DRB1*1101 DQA1*0501 DQB1*0301 haplotype with Dermatophagoides spp.-sensitive asthma in a sample of the Venezuelan population.

BACKGROUND: Genes linked to the major histocompatibility complex (MHC), have been implicated in atopic asthma. Asthma is highly prevalent in the Venezuelan population (estimated at 20%) and genetic markers are needed to identify populations at risk and plan intervention strategies. OBJECTIVE: To study the influence of the MHC class I and class II genes in the susceptibility to atopic asthma. METHODS: MHC-class I HLA-A, -C, -B and MHC-class II HLA-DR, -DQ, -DP gene haplotype frequencies were determined in 135 Venezuelan mestizos, 71 belong to 20 atopic asthmatic families and 64 unrelated controls. The index cases were 20 atopic asthmatics with positive skin-prick tests and specific serum immunoglobulin E (IgE) for Dermatophagoides pteronyssinus (Der p) and Dermatophagoides farinae (Der f). To ascertain the genes associated with susceptibility to atopy and/or asthma, two control groups were studied, 41 non-atopic subjects with skin-prick negative test, and undetectable levels of specific IgE and 23 non-asthmatic atopic subjects with detectable specific IgE to Der p and Der f. A linkage analysis was performed in those families with two or more atopic siblings (with or without asthma). RESULTS: MHC-class I genes analysis showed that HLA-Cw7 was absent in the asthmatic patients studied, whereas the frequency of this allele was 14.3% in non-atopic controls (P = 0.0 17, PC = 0.19) and 20.8% in the atopic controls (P = 0.0066, PC = 0.07). MHC-class II gene analysis showed a significant increase of the HLA-DRB1*11 in the asthmatic patients compared with non-atopic controls (allele frequencies of 25.6 vs 4.4% P = 0.0017, PC = 0.02). There were no significant differences among asthmatic and atopic controls in the frequency of HLA-DRB1*11 (25.6 vs 17.4%). In contrast, the HLA-DRB1*1101+ haplotypes were significantly higher in asthmatics compared with atopic and non-atopic controls (19.6% vs 2.2% vs 2.3%, PC<0.05). The HLA-DRB1*1101, DQA1*0501, DQB1*0301 haplotype was found significantly increased in the patients vs non-atopic controls (15.4 vs 1.1%, PC< 0.01). The serum levels of specific IgE were detectable in both atopic asthmatics and atopic controls; however, it was higher in atopic asthmatics vs atopic controls Der p (median, 58.7 vs 2.7 kU/L, P<0.001) and Der f (median, 46.9 vs 2.7 kU/L, P<0.001). No linkage between MHC genes and mite-atopy could be documented on informative families with two or more atopic siblings. CONCLUSIONS: We have identified an association between the haplotype HLA-DRB1*1101, DQA1*0501, DQB1*0301 and atopic asthma that confers susceptibility to develop mite-sensitive asthma to atopics (relative risk, RR 8.2), and to non-atopic controls (RR = 15.8) that carry this haplotype. Conversely, the allele HLA-Cw7 was absent in the asthmatics studied and had higher frequencies in the atopic (RR = 0.05) and non-atopic (RR = 0.08) controls. Thus, it may have a protective role for developing atopic asthma in the population studied.