Rapid expulsion of Trichinella spiralis in suckling rats: mediation by monoclonal antibodies

Pups born to rats immunized with the excretory/secretory antigens (ESA) of Trichinella spiralis L1 larvae expressed rapid expulsion when challenged orally. Rat monoclonal antibodies specific for ESA were produced and tested for their specificity in Western blots, binding to intact larvae and protective capacity in suckling rats. Eight antibodies had apparently identical specificity in Western blots, each recognizing a polypeptide family that included three molecular weight species sized at 41,000-50,000 MW. These polypeptides formed a series of higher molecular weight aggregates that were also bound by the monoclonal antibodies. Four of eight antibodies were protective when serially transferred to suckling pups. Each protective antibody was able to bind to intact larvae. Antibodies of two subclasses, IgG1 and IgG2c, were strongly protective, delivering to pups the capacity to expel as much as 94% of the challenge dose.

Effect of dexamethasone on Fc gamma receptor expression in foetal and neonatal rat gut

When injected into 12-day-old suckling rats, dexamethasone caused a precocious disappearance of Fc gamma receptors from enterocytes of the proximal small intestine. However, dexamethasone appeared to be necessary for the maintenance or production of such receptors in foetal rat gut cultured in vitro.

Lacteal immunity to enteric cryptosporidiosis in mice: immune dams do not protect their suckling pups

The susceptibilities of passively immunized principal and nonimmunized control suckling mice to orogastric challenge with Cryptosporidium parvum oocysts were compared. Principals were suckled by dams that had recovered from C. parvum infection. Controls were suckled by dams reared free of C. parvum infection. Principals and controls were equally susceptible to challenge. Principals were susceptible even when their dams were hyperimmunized by oral and parenteral booster inoculations with C. parvum oocysts. Immune dams produced serum antibody against C. parvum, while nonimmune dams did not. Anti-cryptosporidia immunoglobulin G (IgG) and IgA were demonstrated in whey extracted from the stomachs of principals that had suckled immune dams but not in whey extracted from the stomachs of controls. It was concluded that passive lacteal immunity is not an efficient means of protection against cryptosporidiosis in mice. As in other coccidian infections, protective immunity against cryptosporidiosis may depend more on immune cells than on antibody.

Polymerized serum albumin beads possessing slow release properties for use in vaccines

Experimental vaccines have been made by co-polymerizing virus particles and virus subunits into rabbit serum albumin beads. When injected into rabbits these model vaccines induced specific humoral antibody production and mimicked vaccines prepared using Freund's incomplete adjuvant. No adverse reactions occurred in experimental rabbits and no antibodies reacting with polymerized rabbit serum albumin beads were found. Immunostimulation is attributed to a slow release of antigen coinciding with the gradual breakdown of bead structure.

Characterization of the immune mediator of rapid expulsion of Trichinella spiralis in suckling rats

In order to identify and characterize the mediator(s) of rapid expulsion, infant rats were passively immunized against oral challenge with 200 infectious Trichinella spiralis muscle larvae by oral or intraperitoneal (i.p.) administration of secretions or sera from infected rats. Milk whey from infected dams provided a modest level of protection when fed to pups. Immunoglobulins from T. spiralis-infected rat serum protected suckling pups when injected intravenously (i.v.) into lactating dams 2 days prior to pup challenge. Intraperitoneal injection of pups with serum immunoglobulins also enabled them to express rapid expulsion. The protective component of serum was precipitated with 40% (NH4)2SO4 and was not affected by heating to 56 degrees, although antibodies mediating passive cutaneous anaphylaxis were inactivated by both treatments. Oral transfer of biliary immunoglobulins collected from infected rats at various times during a primary infection provided no protection to pups. However, serum immunoglobulins from rats infected for 42 days or longer transferred rapid expulsion to pups. Absorption of protective serum immunoglobulins with subclass-specific reagents revealed that IgG1 played a significant role in protection.

Uptake of lymphocytes fed to suckling rats. An autoradiographic study of the transit of labeled cells through the neonatal gastric mucosa

To determine the potential for transfer of maternal lymphocytes to the newborn during suckling, radiolabeled cells were fed to rat neonates of different ages and autoradiographs prepared from tissue sections obtained from the stomach and small intestine. The entire stomach (including contents) and intestinal walls were observed using semiserial 3 micron methacrylate plastic sections. For these studies 100 X 10(6) [3H]uridine-labeled lymph node cells were fed to 1-4-day-old neonates using a smooth-tipped intubation needle. Some of the lactating female rats had been given radioisotope prior to delivery and "cold" babies were fostered to them to enhance the number of labeled cells in the neonatal digestive tract. Babies were killed at 1, 2, 4, 8, 24 and 48 h after feeding. The stomach contents showed a considerable number of labeled cells (32% at 1 h after feeding) and many of these cells were in close proximity to the epithelium. The gastric epithelium often exhibited gaps between adjacent epithelial cells similar to those we have previously reported in the lactating mammary epithelium, and labeled cells were observed in the immediate area of the gaps. Labeled cells were seen in the neonatal gastric epithelium, lamina propria, mesenteric attachments, in the wall and lumen of small gastric blood vessels and adjacent lymph nodes. Labeled cells were most abundant in the gastric wall at 1-2 h following feeding, indicating that transit through the epithelium occurred rapidly. Although labeled cells were seen in the lumen of the small intestine, none were observed in the tissues of the intestinal wall. When heat-killed labeled cells were fed, no labeled cells were seen in the tissues of the neonatal gastrointestinal tract. It is apparent from these studies that a portion of the leukocytes that are delivered to the neonate during suckling are able to transit the gastric epithelium and establish themselves in the neonate's tissues, presumably to aid in the protection of the immunologically naive infant.

F41 pili as protective antigens of enterotoxigenic Escherichia coli that produce F41, K99, or both pilus antigens

Pigs suckling dams that have been vaccinated with pilus antigen are protected against challenge with enterotoxigenic Escherichia coli (ETEC) strains that express the same pilus antigen. However, some ETEC strains express more than one pilus antigen. Pregnant swine were vaccinated either with E. coli HB101 that harbored a recombinant plasmid coding for F41 expression (F41+) or with the HB101 parent strain that carries the pHC79 vector (F41-). Suckling pigs born to vaccinated dams were challenged with ETEC that expressed either K99, F41, or both pilus antigens. Production of F41 in vivo was demonstrated by immunofluorescence assay of sections of ileum and by seroconversion against F41 antigen by pigs challenged with F41+ and K99+ F41+ ETEC strains. The F41+ vaccine protected against challenge with an F41+ ETEC strain. In contrast, F41+ vaccination did not protect against challenge with K99+ or K99+ F41+ ETEC strains. The F41- vaccine did not protect against challenge with any strain used. The results indicate that K99+ F41+ ETEC strains produce F41 antigen in the small intestine during disease and that F41+ vaccination can be a protective antigen if the challenge strain expresses only F41 antigen, but that F41+ vaccination may not protect against strains that produce both K99 and F41 antigens.

Cytotoxic activity of sera from diabetic BB rats against BB rat islet--a functional study

[3H] leucine incorporation into islet proteins, insulin secretion, hormone content (insulin, glucagon) and DNA synthesis were measured in cultured BB rat islets in a study to compare the effect of freshly prepared BB rat serum obtained from non-diabetic and newly diagnosed diabetic BB rats on islet functions. After exposure of isolated BB rat islet to a mixture of tissue culture medium and BB rat serum (1:1) for 24 hr, islet lysis was induced by 40% of the diabetic BB rat sera whereas the remaining 60% of diabetic BB rat sera tested did not influence islet functions as evidenced by insulin net production, glucose-induced insulin release and DNA synthesis measured in a subsequent culture period in TCM 199, 10 mmol/l glucose supplemented with 10% neonatal calf serum or short-term incubations. After exposure of islets to sera with anti-islet cytotoxicity the majority of islet cells were destroyed as indicated by a drastically reduced [3H] leucine incorporation into islet proteins and by a diminution of hormone and DNA content of islets. This toxicity against islets was overcome by heat treatment (58 degrees C, 30 min) of sera. The results indicate that heat-labile components in certain diabetic sera of BB rats can lyse the majority of islet cells in BB rat islets within 24 hr. Our assay may help to dissociate humoral and cellular components which cause the injury of beta cells and the onset of diabetes in BB rats.

Immune responsiveness in offspring of adoptively immunized mothers

The rate of appearance of cells forming 19S hemolytic antibody (PFC) in the spleens of F1 newborn mice after adoptive anti-paternal immunization of fetuses, newborns and/or their mothers during pregnancy has been studied. An increase in the number of PFC was found at the age of 6 to 11 days in offspring of adoptively immunized mothers. These newborns, even when foster nursed by untreated mothers, still had a significantly higher number of PFC in comparison to the controls. In contrast, adoptive immunization of the newborns themselves resulted in a decrease of PFC during the second week after birth. Several possible explanations for the obtained results are discussed including the putative transplacental passage of immunocompetent cells.

Passively acquired immunity in the newborn of a marsupial (Monodelphis domestica)

A colony of fully pedigreed Monodelphis domestica has been used to investigate the maternal-fetal relationship in this unique marsupial species. To determine how immunity is transferred from mothers to young in M. domestica, we hyperimmunized females with sheep red blood cells (SRBC) before and during gestation. Offspring from these females were collected at various times after birth, and saline extracts of the neonates were assayed for hemolysins against SRBC. Antibodies were present in extracts of newborn that had been allowed to suckle their mothers; none were detected in extracts of infants that were not allowed to suckle. Antibodies were present in the milk of immunized mothers, but were not detected in the milk of nonimmunized mothers. The titer of antibodies in the extracts of newborns generally increased proportionately to the time that the newborn had been allowed to suckle. We conclude that the transfer of passive immunity from mothers of M. domestica to their offspring occurs primarily via the milk.

Immune response in sows given transmissible gastroenteritis virus or canine coronavirus

Twelve pregnant sows were inoculated oral-nasally 8 weeks before farrowing with attenuated transmissible gastroenteritis virus (TGEV), tissue culture-adapted canine coronavirus (CCV), or fluids from mock-infected culture (controls). A 2nd dose of the same inoculum, one-half oral-nasally and one-half intramammarily, was given 6 weeks later. Neutralizing antibodies for TGEV and CCV were demonstrated in sera, colostrum, and milk whey from the virus-vaccinated sows. Homologous geometric mean neutralizing titers were generally 4-fold higher than were heterologous titers. After challenge exposure of the nursing pigs with virulent TGEV, average morbidity and mortality for the pigs were 81% and 34% (mortality range = 11% to 63%), respectively, in the TGEV-vaccinated group; 83% and 39% (mortality range = 15% to 83%), respectively, in the CCV-vaccinated group; and 97% and 84% (mortality range = 78% to 100%), respectively, in the controls. Seemingly, sera from swine exposed to CCV could test serologically positive for TGEV-neutralizing antibody, and TGEV and CCV share at least 1 common neutralizing determinant that may be involved in protection.

A double-protease-resistant variant of transmissible gastroenteritis virus and its ability to induce lactogenic immunity

A virus resistant to 2 major intestinal proteases (trypsin and alpha-chymotrypsin) was derived from the attenuated Purdue strain of transmissible gastroenteritis virus. Its enzymatic stability was confirmed, in vitro, by exposure to proteolytic enzymes and to porcine intestinal fluids. Vaccination of 5 seronegative pregnant sows with the variant virus by a series of 2 oral and 1 IM inoculations resulted in high titers of neutralizing antibody in serum and colostrum. The mean antibody titer in milk whey decreased 44-fold within 1 week after parturition. At 3 days of age, the 40 pigs delivered by these sows were challenge exposed orally with virulent transmissible gastroenteritis virus. Pigs nursing the 5 vaccinated sows underwent a relatively mild clinical course of illness. The average mortality of these 40 pigs was 33%. Thirty-six pigs which had been raised by 4 nonvaccinated sows had a more severe illness, greater daily weight loss, and higher mortality (92%).

Effect of immunoneutralization of thyrotrophin-releasing hormone on the release of thyrotrophin and prolactin during suckling or in response to electrical stimulation of the hypothalamus in the anaesthetized rat

The aim of the present study was to use the technique of immunoneutralization with anti-thyrotrophin-releasing hormone (anti-TRH) serum to investigate the role of TRH in mediating the TSH and prolactin responses to electrical stimulation of the hypothalamus and the prolactin response to suckling in lactating rats. Electrical stimulation of either the median eminence or paraventricular nuclei of male or female rats anaesthetized with urethane resulted in significant increases in the plasma concentrations of both TSH and prolactin. Injection of sheep anti-TRH serum blocked the rise in plasma TSH concentration in response to stimulation of either brain area, but did not block the increase in plasma prolactin concentration. In anaesthetized, lactating female rats, the suckling stimulus produced a significant increase in the plasma prolactin concentration, but did not alter the plasma TSH concentration. Injection of anti-TRH serum, but not control non-immune or anti-bovine serum albumin, significantly decreased the basal release of TSH but did not abolish the prolactin response to suckling. These results show that TRH is the principal mediator of the neural control of TSH release in the rat, but is not crucial for the release of prolactin in response to either hypothalamic stimulation or suckling.

Maternally derived immunity in young mice to infection with Trypanosoma brucei and its potentiation by Berenil chemotherapy

Young mice which were allowed to suckle, from birth, a mother infected with Trypanosoma brucei, or a mother whose infection had been cured before parturition with Berenil chemotherapy, were themselves immune to homologous trypanosome challenge. This immunity extended until approximately 25 days of age, and was transmitted in the colostrum/milk of the mother. Mice born of infected mothers, but transferred at birth to normal foster mothers, were susceptible to trypanosome infection. Drug prophylaxis in normal newborn mice was also effective for approximately 25 days, but in mice which, in addition, received colostral antibody from the mother, combined immunochemoprophylaxis protected the offspring for 40-50 days. Since the combination of protective strategies continued to resist challenge beyond the stage when, on its own, each component's efficacy had decayed, it may be of practical value as an approach to improved disease control under certain field conditions where trypanosomiasis prevails.

Enzyme-linked immunosorbent assay for the measurement of immunoglobulin G concentrations in porcine plasma and colostrum

An enzyme-linked immunosorbent assay is described for the estimation of porcine immunoglobulin G in either colostrum or plasma samples. The inter-assay coefficient of variation was 9.1 per cent and the intraassay coefficient of variation was 7.2 per cent. The repeatability or intra-class correlation coefficient of the assay was 0.9. The assay proved to be a sensitive, inexpensive and rapid method for assessing the immune status of pigs.

Adoptive transfer studies demonstrating the antiviral effect of natural killer cells in vivo

We carried out adoptive transfer studies to determine the role of natural killer (NK) cells in resistance to murine cytomegalovirus (MCMV) and lymphocytic choriomeningitis virus (LCMV). We transferred leukocytes from adult mice into suckling mice 1 d before injecting them with virus. Resistance was measured by enhancement of survival and reduction of virus multiplication in the spleens of recipient mice. The phenotype of the cell population capable of mediating resistance to MCMV was that of a nylon wool-nonadherent, asialo GM1+, NK 1.2+, Ly-5+, Thy-1-, Ia-, low density lymphocyte; this is the phenotype of an NK cell. Cloned NK cells, but not cloned T cells, provided resistance to MCMV in suckling mice. Cloned NK cells also provided resistance to MCMV in irradiated adult mice, and antibody to asialo GM1, which depletes NK cell activity in vivo, enhanced the synthesis of MCMV in athymic nude mice. Neither adult leukocytes nor cloned NK cells influenced LCMV synthesis in suckling mice. We conclude that a general property of NK cells may be to provide natural resistance to virus infections, and that NK cells can protect mice from MCMV but not from LCMV.

Functional and ultrastructural evaluation of neutrophils from foals and lactating and nonlactating mares

Neutrophils from 4 pony foals, 3 lactating pony mares, and 3 nonlactating mares were evaluated ultrastructurally and by in vitro function tests. Neutrophils from foals had significantly (P = 0.05) less random migration than neutrophils from mares; values in tests for iodination and Staphylococcus aureus ingestion were also lower with foal neutrophils. Neutrophils from lactating mares had lower responses to iodination, antibody-dependent cell-mediated cytotoxicity, and random migration tests than did neutrophils from nonlactating mares. Ultrastructurally, granule concentration did not differ significantly among groups. A slight decrease in primary granules and a corresponding increase in granules with a flocculent matrix indicates partial spontaneous neutrophil degranulation in foals and lactating mares.

Persistence of passively acquired antibodies to hemagglutinating encephalomyelitis virus in swine

The persistence of passively acquired antibodies to hemagglutinating encephalomyelitis virus (HEV) was determined in 4 pigs in each of the litters of 10 sows. At time of delivery by the sows, the colostrum and serum samples (from the 10 sows) had hemagglutination-inhibiting antibodies to HEV. All of the pigs also had hemagglutination-inhibiting antibodies to HEV at 2 days of age. The level of circulating antibodies to HEV decreased at a nonlinear rate and persisted for about 4 to 18 (mean 10.5) weeks in the circulation of pigs. All 40 pigs were seronegative at 20 weeks of age.

Alteration of antibody-mediated responses of suckling mice to T-cell-dependent and independent antigens by maternal marginal zinc deficiency: restoration of responsivity by nutritional repletion

To further characterize the effects of marginal zinc deficiency on the development of the immune system of the suckling A/J mouse, dams were fed marginal (1.6 micrograms Zn/g), intake restricted (30 micrograms Zn/g) or adequate (30 micrograms Zn/g) levels of dietary zinc days 5-17 postpartum. Marginal levels of zinc had little effect on the body weight of dams; however, their pups were only 71-75% the weight of control pups. In response to two T-cell independent (TI) antigens pups of low zinc dams could produce only 49 and 44% as many antibody-producing cells per spleen as control pups. Pups of restricted-fed dams produced about 60% as many cells as controls for each TI antigen. The avidities of the plaques produced by pups of restricted and control dams in response to TI antigens were nearly the same but were 5.5 times higher than the relative avidities of the antibodies produced by pups of low zinc dams. The responses of the deficient pups to sheep red blood cells (SRBC), a T-dependent (TD) antigen, were 25-30% of response of control and 56-75% of that of restricted pups depending on whether direct (IgM) or indirect (IgG) plaques were enumerated. The data demonstrate that marginal deficiencies in zinc during lactation greatly reduce the ability of suckling pups to mount antibody-mediated responses and suggest that the kinds of lymphocyte subsets found in deficient pups are altered. However, antibody-mediated response capacity was normal in the deficient pups following a short period of zinc supplementation.

Rotavirus associated diarrhoea in nursing piglets and detection of antibody against rotavirus in colostrum, milk and serum

A blocking method of ELISA for the detection and quantification of antibody against porcine rotavirus in serum, colostrum and milk has been compared with a plaque reduction test. The results obtained with the two techniques correlated (Fig. 1). Antibody against rotavirus was demonstrated in 384 serum samples representing 25 swine farms, indicating a widely spread and dense distribution of the infection with porcine rotavirus among Danish swine. The antibody contents in milk samples from 7 gilts and sows from 2 farms with a previously diagnosed problem with rotavirus associated diarrhoe showed a rapid decline during the first few days of the lactation periods (Fig. 1). An increase in the contents of rotavirus specific antibody was observed from day 15 in the milk samples from one of the gilts. The excretion of rotavirus with feces from the 7 litters of piglets were followed through the suckling period. Rotavirus war found in all litters but one and the virus was excreted in periods ranging from 4 to 9 days.

Demonstration that milk cells invade the suckling neonatal mouse

Mouse milk cells were stained with rhodamine or fluorescein isothiocyanate and fed to young suckling mice. By visual examination of serial sections and by flow cytofluorometry, we were able to demonstrate directly the presence of these cells in peripheral tissues. It was estimated that at least 0.1% of the fed cells might infiltrate the young mouse, which is initially immunologically defenseless. This is in accordance with evidence from many sources for activity of maternally-derived lymphoid cells in young rodents.

Early nutritional experiments: effects on the humoral and cellular immune responses in mice

Studies were carried out to determine the effect of varying intake during the suckling period on the immune responses of mice. Female mice were bred in litters of 4, 9 or 20 pups. Litters of nine pups were considered control groups. Overfeeding (litters of 4) during this period did not change the serum protein profile nor the humoral and cellular immunity of the weanling mice, as judged by their plaque-forming cell responses to SRBC and lymphocyte stimulation in vitro by Con A or LPS. Conversely, mice bred in large litters showed, at weaning, decreased serum levels of albumin and alpha-globulins but did not exhibit marked alterations of their immune responses, although they were in a severe state of protein-energy deficiency. After weaning, feeding a normal diet ad libitum normalized all the altered parameters tested in the malnourished mice. However, when malnutrition was followed by intermittent feeding, the studied immunological functions were significantly affected: the humoral, as well as the cell-mediated immune responses were depressed. These observed alterations were not related to changes in the levels of serum corticosterone or zinc. Our findings suggested that differences in the length of dietary deficiency rather than its severity may explain some of the conflicts in reports on functional immune tests in protein-energy malnutrition.

Effect of maternal dietary zinc on growth and mitogenic responsiveness in suckling mice

The effects of varied levels of maternal dietary zinc on growth and immunological development of suckling A/J mice were studied. From 5 days postpartum, lactating dams were fed biotin-fortified egg-white diets containing the following levels of zinc: 1.6 microgram/g (low zinc), 3.6 microgram/g (intermediate zinc), 5.8 microgram/g (moderate zinc) and 30 microgram/g (control). At 17 days of age, low zinc pups exhibited reduced body weight gain (70%), smaller thymuses and spleens, and reduced splenocyte numbers (18%). Intermediate zinc pups had normal body weights but slightly reduced spleens and thymuses; moderate zinc pups were unaffected. Since suckling mice are not fully immunocompetent, splenic mitogenic responses to phytohemagglutinin (PHA), concanavalin A (Con A), lipopolysaccharide (LPS), pokeweed mitogen (PWM), and dextran sulfate (Dx) were used to evaluate the status of various lymphocyte subpopulations. Neonates from the low zinc group gave no Con A response and limited responses to LPS and PWM (50%). Intermediate zinc pups responded satisfactorily to all mitogens except LPS (64%); moderate zinc pups responded normally. It was concluded that 5.8 microgram/g maternal dietary zinc, fed day 5-17 postpartum, is adequate for normal neonatal growth and mitogenic responses. Conversely, 1.6 microgram Zn/g caused neonatal growth retardation and reduced mitogenic responses without excessive mortality.

Modified human immune serum globulin for intravenous administration: in vitro opsonic activity and in vivo protection against group B streptococcal disease in suckling rats

Human immune serum globulin (ISG) preparations were tested in an in vivo suckling rat protection assay and an in vitro opsonophagocytic assay against various types and strains of Group B streptococci (GBS). Standard ISG provided minimal protection in suckling rats against type III GBS sepsis, whereas preparations of ISG modified for intravenous administration (MISG) provided significant protection against all strains of type III, type II and type Ia GBS tested. Although less protection was obtained against type Ia strains, the survival in suckling rats challenged with all types of GBS varied from 73% to 91% with MISG therapy, as compared with 5% to 12% survival in untreated animals. In this in vivo model, MISG was protective even when administered after bacterial challenge, but had to be administered within 5 h of infection. MISG also had high in vitro opsonic activity against GBS types III and II, but was less effective with some type Ia strains. Just as MISG was more protective than ISG in vivo, it also was more opsonic in vitro. A detailed comparison of one lot of MISG with its parent ISG revealed that the modified preparation actually contained less IgG. When equivalent concentrations of affinity-purified IgG from both preparations were tested, the IgG from MISG was significantly more opsonic. Since the affinity purification procedure eliminated the possibility that IgM or substances introduced in the modification process were actually responsible for the enhanced bactericidal activity, it appears that the individual IgG molecules in MISG may be more effective. These studies suggest that MISG which has been modified by reduction and alkylation for intravenous administration may provide a valuable adjunct to chemotherapy in the treatment of GBS disease in the neonate.

The protection of lambs from eperythrozoon infection while suckling Eperythrozoon ovis carrier ewes

When lambs born to and suckling Eperythrozoon ovis carrier ewes were inoculated with heparinised blood containing large numbers of E. ovis organisms, the lambs were either sterilised of the infection or patent infection was suppressed till the lambs were weaned. In vitro infection, transplacental transfer of antibodies or soluble antigens could not be demonstrated.

Provocation of allergic response by supplementary feeds of cows' milk

The postweaning IgE and IgG antiovalbumin antibody responses were greater in rat pups which had received a cows' milk-based supplementary feed than in litter mates which had not. This effect was antigen non-specific and might be similar to that of supplementary feeds in the development of atopy in human infants. The total IgE concentration was similar in the two groups. Supplementary feeds did not increase the low values of IgE antiovalbumin in rats suckled by mothers immunised to ovalbumin.

Analysis of age-dependent resistance to murine coronavirus JHM infection in mice

Resistance to intraperitoneal murine coronavirus JHM infection in mice develops with age. C3H mice were found to be fully susceptible up to the age of 20 days and resistant after 23 days of age. Protection of susceptible animals from death due to infection could be achieved by maternal antibodies or by transfer of spleen cells from immunized, but not from nonimmunized, donor mice. Lack of protection by transfer of unprimed adult spleen cells was not related to immunosuppression by the host. Moreover, resistance of adult mice could not be abrogated by application of lymphocytes from suckling mice, although immune suppression by other means did affect the resistance of adult animals. On the other hand, spleen cells from nonimmunized mice could be primed with inactivated JHM virus in suckling mice and protected these mice from death due to a subsequent virus infection. Thus, the outcome of infection with JHM virus in suckling and adult mice can be influenced by immunological events, but is not exclusively due to the different stages of immune competence.

Rheumatoid factor-like immunoglobulin M protects previously uninfected rat pups and dams from Trypanosoma lewisi

The serum of lactating rats that have never been infected with the protozoan parasite Trypanosoma lewisi contains a rheumatoid factor-like immunoglobulin M (IgM). This IgM amplifies a specific immunoglobulin G (IgG) response to the parasite and accounts for the unusual resistance of previously uninfected lactating rats and their suckling pups to infection with T. lewisi. A similar rheumatoid factor-like IgM, which is induced late in the usual course of infection with T. lewisi in nonlactating rats, amplifies an earlier IgM response and terminates the infection. To our knowledge, this is the first description of a rheumatoid factor, which is classified as an autoimmune antibody, acting in a protective manner.

Levamisole: potentiation of primary immunoglobulin M antibody responses in suckling rats

The influence of levamisole (LMS) on the primary immunoglobulin M (IgM antibody response of suckling rats was investigated. Although suckling rats did make a direct plaque-forming cell (PFC) response to sheep red blood cells (SRBC), the magnitude of this response was much lower than that of adult rats. LMS treatment (2.5 mg/kg) markedly potentiated the anti-SRBC response in 10-day-old rats, but this enhanced PFC response never attained adult levels. In contrast, LMS failed to boost the anti-SRBC response of adult rats, although the adult response to suboptimal antigenic stimuli was enhanced. The ontogeny of immunological responsiveness to SRBC was not influenced by LMS; only existing responses could be modulated. The potentiating effect of LMS was dose-dependent, with high doses causing suppression. The influence of LMS did not involve the earlier appearance of PFC. Since LMS augmented the PFC response to SRBC when administered before or after antigen, it appears that both the inductive phase and the proliferative phase of antibody production can be modulated. Finally, the PFC responses to a more thymus-independent antigen (2,4,6-trinitrophenyl-Ficoll) was boosted, suggesting that LMS may be capable of directly influencing B lymphocytes. These findings indicate that the functional immunodeficiency of the neonatal antibody response can be improved by LMS treatment.

Protection against infection with Giardia muris by milk containing antibody to Giardia

Mice ingesting milk from immune mothers are protected against infection with Giardia muris. In order to be protected, the infant mice must be suckling immune milk at the time of challenge with the parasite and must continue to do so for at least three to five days thereafter. Suckling immune milk does not induce sustained immunity; infants become susceptible to infection after weaning begins at 14 days of age. Immune milk contains specific IgA and IgG antibody to Giardia, which may be the mediators of the demonstrated protection. The properties of this protection are similar to those described for protection against other enteric infections by milk.

Influence of the immune system on the course of infection with murine coronavirus JHM in suckling mice

The course of infection with murine corona virus JHM in C3H mice depends on the age of the animals. Mice up to 20 days of age are fully susceptible while mice older than 23 days resist the infection. Protection of suckling mice from death of infection can be provided by intraperitoneal administration of immune spleen cells but not by non-immune spleen cells from adult mice. The immune spleen cells can be generated by priming adult mice, or by priming non-immune spleen cells from adult mice in baby mice with inactivated JHM virus. Thus the immune system might well be involved in the different outcome of infection with JHM-virus in suckling and adult mice, but it does not seem to be the exclusive factor responsible for the achievement of natural resistance.

Mild transmissible gastroenteritis in pigs suckling vaccinated sows

A strain of transmissible gastroenteritis (TGE) virus of low virulence was isolated from 14-day-old pigs suckling sows vaccinated with an attenuated TGE vaccine. Diarrhea developed in suckling pigs approximately 14 days after farrowing in 4 farrowings; however, none of these pigs died from diarrhea. Diarrhea ceased after the 4th farrowing, when vaccination of sows was discontinued. Experimentally, both the field isolate and the vaccine strain were infective and in some instances lethal for 2-day-old pigs exposed orally; however, neither strain was as virulent as the Purdue strain.

Transport of immunoglobulins from serum into colostrum

Oligomeric, J-chain-containing immunoglobulins were observed to be transferred selectively from serum into colostrum. These studies suggest that, in the case of the mammary gland secretion, a significant role for extraglandular synthesis of IgA merits consideration. Thus, for example, colostrum may contain antibodies synthesized locally as well as antibodies synthesized in the much larger lymphoid tissues such as the gut lamina propria.

Colostrum production by ewes and the amounts ingested by lambs

Studies involving 49 ewes which were well nourished during the last eight weeks of pregnancy indicated that ewe weight loss during pregnancy and lamb birth weights followed the recognised pattern and were within acceptable "normal" limits. Colostrum production ranged from 1238 to 4593 g per ewe during the 48 h following the first suckling and there was evidence that production levels were related to demand by the lambs. Colostrum consumption by individual lambs was related to litter size. The smaller the litter size the greater was the amount ingested during the first 48 h of life. No clear relationship was established between the amount of colostrum consumed and the level of immunoglobulin in a lamb's circulation. Possible reasons for this are discussed.

Direct evidence for pH-dependent Fc receptors on proximal enterocytes of suckling rat gut

By means of an erythrocyte-antibody rosette technique, Fc receptors, functional at pH 6.0 but not at 7.2, were shown to be present on enterocytes isolated from duodenum and jejunum (but absent from ileum) of 12-20-day-old suckling rats.

Myelin basic protein serum factor. An endogenous neuroantigen influencing development of experimental allergic encephalomyelitis in Lewis rats

Age-related concentrations of myelin basic protein serum factor (MBP-SF), an endogenous neuroantigen detected and quantitated by inhibition of binding of rat myelin basic protein (RMBP) antibody with 125I-RMBP reagent antigen and immunochemically indistinguishable from native RMBP in this respect, reach peak levels as high as 21 ng/microliter among 2-3-wk-old normal suckling Lewis rats. Levels then progressively decline to low, usually undetectable levels of less than or equal to 0.6 ng/microliter MBP-equivalents in adult animals by 7 wk of age. MBP-SF levels are inversely related to the age-related increasing capacity of maturing Lewis rats to develop experimental allergic encephalomyelitis (EAE) after sensitization to MBP of syngeneic, but not xenogeneic, origin. MBP-SF appears to be an endogenous neuroimmunoregulatory product of potential importance for immunologic tolerance to autologous RMBP in Lewis rats.

Development of peripheral B and T lymphocytes in piglets

The percentage of B and T lymphocytes in the peripheral blood of piglets during their first 35 days of life was estimated by means of the immunofluorescence-labelled anti-L chains sera and the spontaneous E-rosette techniques. The mean values obtained for adult pigs PBL were 23.8 +/- 10.2% of B and 38.0 +/- 8.4% of T lymphocytes. The piglets showed a linear increase for the B lymphocytes starting from a mean value of 4% observed for the newborns. The trend of the T lymphocytes was represented by a bimodal curve. It starts for newborns at 3% and shows a change in shape by the 10th day. It is suggested that the piglets have adult levels of B and T lymphocytes by the time of weaning.

Immunization of suckling pigs against enteric enterotoxigenic Escherichia coli infection by vaccinating dams with purified pili

Pregnant swine (gilts) were vaccinated parenterally with a suspension of purified pili from the porcine enterotoxigenic Escherichia coli strain 987 (09:K103::NM). Gilts injected with placebo served as controls. Suckling pigs born to gilts in both groups were challenged intragastrically with virulent strain 987. The percentage of deaths, incidence and duration of diarrhea, numbers of E. coli in the ilea, and E. coli attachment to the villous epithelia were significantly less in suckling pigs of vaccinated gilts than in those of controls. These results are consistent with the hypothesis that pili of some enterotoxigenic E. coli facilitate adhesion to intestinal epithelia. Vaccination of dams with pili appears to be a means of immunizing against diarrheal disease caused by enterotoxigenic E. coli in suckling neonates. This work confirms the role of somatic pili as colonization and virulence factors and provides another example of safe and effective purified pilus vaccines.