Toxicological consequences of feeding PCB congeners to infant rhesus (Macaca mulatta) and cynomolgus (Macaca fascicularis) monkeys

In a study designed to minimize interspecies extrapolation of toxicological data, nine rhesus (Macaca mulatta) and 15 cynomolgus (M. fascicularis) day-old infant monkeys were separated from their dams following parturition and hand-reared using a liquid non-human primate formulation. The infants were randomly divided into a control and a treated group which received a mixture of polychlorinated biphenyl (PCB) congeners analogous to those found in breast milk from Canadian women. The concentration of congeners in the dosing media resulted in each infant receiving a total of 7.5 microg PCB congeners/kg body weight/day. The congeners were added either to the liquid formulation or to corn oil and administered to the back of the monkey's mouth for 20 weeks. Monthly blood and adipose specimens were obtained during the dosing period and then periodically until the monkey was necropsied or taken off test (minimum of 66 weeks on test) for congener analysis. Parameters such as body weight, formula consumption, tooth eruption, somatic measurements, haematology and serum biochemistry were monitored throughout the study. In addition, a qualitative evaluation of the absorption and depletion of the various congeners was undertaken as was an immunological evaluation. For the monitored parameters, very few differences were found to be statistically significant. For the immunological parameters, the only statistically differences found were a reduction over time for immunoglobulins M and G antibodies to sheep red blood cells (cyno, P = 0.025; rhesus, P = 0.002) and a treatment-related reduction in the levels of the HLA-DR cell surface marker (mean percent, P = 0.016; absolute levels, P = 0.027). There were some qualitative differences regarding absorption and depletion rates for the various congeners, but it could not be definitely ascertained whether these differences were due to species differences or dosing mode. However, statistically significant differences were found for treatment (P = 0.0293) as well as for species and vehicle regarding the concentration of PCB in blood (species;--P = 0.0399; treatment--P = 0.0001) and adipose tissue (species--P = 0.0489; treatment--P = 0.0001).

The role of LY49 NK cell subsets in the regulation of murine cytomegalovirus infections

The distributions and functions of NK cell subsets, as defined by the expression of Ly49 NK cell receptors, were examined in murine CMV (MCMV)-infected mice. MCMV induced a reduction in NK1.1+ cell number in the spleen and an increase in the peritoneal exudate cells. Within the splenic NK1.1+ population, proportional increases in Ly49A+ and Ly49G2+ cells but decreases in Ly49C+ and Ly49D+ cells were observed 3 days post-MCMV infection, but within the peritoneal NK1.1+ cell populations there were proportional decreases in Ly49A+ cells and increases in Ly49C+, Ly49D+, and Ly49G2+ cells. Lymphocytic choriomeningitis virus did not elicit a comparable NK cell subset distribution. Lymphokine-activated killer cells were sorted into different Ly49 NK cell subsets and adoptively transferred into C57BL/6 suckling mice. Regulation of MCMV synthesis in these suckling mice was shown to be an IFN-gamma-dependent, perforin- and Cmv-1-independent process, and each NK cell subset mediated anti-viral activity. In adult C57BL/6 mice, the control of MCMV in the spleen is mediated by a perforin-dependent mechanism, regulated in part by the Cmv-1 gene, which maps closely to the Ly49 family. In vivo depletions of either one or two of the Ly49 subsets in adult mice did not affect the ability of the residual NK cells to regulate MCMV synthesis. These data provide evidence of NK cell subset distribution and function in MCMV infection, but no individual subset was required for the Cmv-1-like regulation of MCMV synthesis.

Neuroendocrine-immune interactions in the neonate

Cytokine responses to lipopolysaccharides in neuroendocrine tissues are age- and tissue-dependent in neonatal pigs. Developmental differences in serum and tissue-specific responses are not necessarily equivalent. Lower levels of cytokine gene expression in neuroendocrine tissues of early neonates potentially could influence neuroendocrine and immune responses to infection. The limited information on neuroendocrine-immune responses and interactions in neonatal farm animals presents significant challenges, as well as opportunities for new discoveries and improvements of livestock production.

Immunoglobulin M serum levels in females and pups of southern elephant seal (Mirounga leonina) during the suckling period

This paper reports Immunoglobulin M (IgM) levels in serum samples from eight female-pup pairs of southern elephant seals (Mirounga leonina), at King George Island, Antarctica. IgM levels were determined on sera obtained from sequential sampling throughout the suckling period (approximately 23 days). The IgM concentration in southern elephant seal serum was measured by single radial immunodiffusion on agarose plates. Female IgM levels (123.5-613.0 mg/dL, n = 8) were significantly higher than pup levels (5.9-123.6 mg/dL, n = 8). Both groups showed an increasing trend throughout the entire suckling period, with significant differences in relation to stages of lactation. Pup IgM levels on the first day of life (mean +/- SD, 7.6 +/- 2.9 mg/dL, n = 3) suggest that endogenous synthesis takes place before birth.

Use of age and serum gamma-glutamyltransferase activity to assess passive transfer status in lambs

OBJECTIVE

To develop an algorithm for predicting passive transfer status of lambs of various ages, using the lamb's age and serum gamma-glutamyltransferase (GGT) activity.

DESIGN

Prospective study.

ANIMALS

51 Suffolk, Columbia, and crossbred lambs from 1 to 16 days old.

PROCEDURE

Serum was obtained from all lambs. Serum GGT activity was measured, using a commercially available kit. Serum IgG concentration was determined by use of radial immunodiffusion. Day-1 serum IgG concentration was estimated from sample IgG concentration, lamb age, and the published 14-day half-life of IgG in lambs. Stepwise multivariate regression models were developed to estimate day-1 serum IgG concentration as a function of the natural logarithm of serum GGT activity (In[GGT]) and natural logarithm of lamb age (In[age]) at the time of sampling. These regression models were then used to calculate serum GGT activities that were equivalent to various day-1 IgG concentrations in lambs of various ages.

RESULTS

In(GGT) and In(age) were significantly associated with estimated day-1 IgG concentration. Day-1 serum IgG concentration could be predicted using the formula: IgG = -7,686 + 1,366(In[GGT]) + 1,199(In[age]). The model was moderately accurate in predicting serum IgG concentration (R2 = 0.52).

CLINICAL IMPLICATIONS

Serum GGT activity can be used to assess passive transfer status of lambs.

Acquired protection of the rabbit (Oryctolagus cuniculus) against coccidiosis using a precocious line of Eimeria magna: effect of vaccine dose and age at vaccination

Sucklings were vaccinated orally once at 25, 27 or 29 days of age with a precocious line of Eimeria magna. Each group received two doses varying from 3.5 x 10(2) to 3.5 x 10(4) oocysts. At 36 days of age, animals received a challenge inoculation with 10(4) oocysts of the wild strain of E.magna. Vaccination reduced oocyst output 10 to 1000 times after the challenge inoculation and prevented the decrease in the weight gain observed in non vaccinated challenged animals. When the vaccination was performed more than 9 days before challenge, full protection was obtained. An individual oral vaccination performed with 3500 oocysts gave total protection whatever the age at vaccination between 25 and 29 days of age.

Reversible effects on B and T cells of the gut-associated lymphoid tissues in rats malnourished during suckling: impaired induction of the immune response to intra-Peyer patches immunization with cholera toxin

To define the alterations provoked by malnutrition during suckling (20 pups/dam) in the gut-associated lymphoid tissues of rats, Peyer patch (PP) and mesenteric lymph node (MLN) cells were studied by flow cytometry. After weaning (21 days of age), rats malnourished during suckling (MNR) showed an increase in the CD4+ CD45RC+ subset together with a decrease in the CD4+ CD45RC- subset (P < 0.01). These alterations remained even after 3 weeks of refeeding with stock diet. The CD4+CD8+ subset was not increased in the MNR, indicating that a release of cortical thymocytes did not occur. At weaning the percentage of CD4+Thy1+ cells was decreased in the MNR, indicating a low number of cells released from the thymus. When the B cell lineage was studied, we found a decreased percentage of precursors in the bone marrow and a decreased percentage of mature B cells in the periphery. When the MNR were immunized intra-PP with cholera toxin (CT) after 1 week of refeeding, the specific IgG and IgA and IgM antibody-forming cells (measured by ELISPOT) were diminished in the PP, MLN, and spleen when compared to the age-matched controls (P < 0.001). These results were coincident with the ELISA titers obtained in the sera and in the intestinal fluids. When CT was administered after 2 weeks of refeeding, the number of IgM anti-toxin AFC approached control values, but the number of IgA and IgG AFC continued to be low. When 3 weeks of refeeding was allowed before the CT delivery, the immune response in the MNR approached control values. These results indicate that malnutrition during suckling provokes alterations in B and T lymphocytes and produces a lack in the induction of the primary and secondary immune responses in the GALT which reversed after 3 weeks of refeeding.

Contribution of passive immunity to porcine respiratory coronavirus to protection against transmissible gastroenteritis virus challenge exposure in suckling pigs

OBJECTIVE

To determine the ability of porcine respiratory coronavirus (PRCV) infections to induce passive immunity in suckling pigs to transmissible gastroenteritis virus (TGEV) challenge exposure. DESIGN AND ANIMALS: 4 TGEV seronegative sows and their litters (group A) served as controls, whereas 2 other groups (B and C) of sows (also TGEV seronegative) were oronasally inoculated with live PRCV during 1 or 2 subsequent pregnancies, respectively.

PROCEDURE

Effectiveness of passive immunity provided to pigs via colostrum and milk was assessed after TGEV challenge exposure, and TGEV antibody responses in colostrum and milk were analyzed.

RESULTS

Mortality in the 3 groups of young pigs correlated with severity of clinical signs of TGEV infection and was highest in control litters (86% in group-A pigs) and lowest in litters of sows inoculated with PRCV in 2 subsequent pregnancies (14% in group-C pigs). Virus-neutralization and IgA and IgG TGEV antibody titers of milk collected from sows at challenge exposure had significant positive correlation with litter survival. Significantly higher numbers of TGEV-specific IgA and IgG antibody-secreting cells were found in group-A pigs than in group-C pigs, suggesting that high titer of maternal antibodies (induced in group-C sows multiply exposed to PRCV) may interfere with active antibody responses.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that, in PRCV-infected pig herds, multiple exposures of pregnant sows are associated with higher IgA and IgG antibody titers to TGEV in milk, and these titers contribute to protection against TGEV infection.

The occurrence of macrophage-like cholera toxin uptake cells in the intestinal villi of suckling rats

An oral administration of cholera toxin (CT. 10m g) caused diarrhea in infant rats ranging in age from 1 to 14 days. After administration of the toxin a time sequence study was carried out using highly sensitive immunohistochemical procedures. CT was exclusively incorporated into a type of macrophage-like (ML) phagocytic cell. These cells were identified within the intestinal epithelium of rats suffering choleraic diarrhea. After 2 hrs cells taking up the toxin markedly increased in number and were found in both the mucosa and the lamina propria mucosae. After 4 hrs a small number of ML cells containing CT were still present in the mucosal epithelium, but were no longer observed in the lamina propria. Two kinds of monoclonal antibodies against rat macrophages were used to gain a clue as to the cytological characteristics of ML cells. ED1- or ED2-positive macrophages were demonstrable in the lamina propria and submucosa of the small intestines from control rats. In CT-treated rats a considerable number of cells positive for CT and ED1, or CT and ED2 antisera, were found within the epithelial cell layer and the lamina propria of intestinal villi. It is suggested that many ML cells responsive to CT, if not all, are ED1 and ED2 macrophages and are resident in the villous lamina propria where they can migrate to uptake CT in the intestinal lumen. CT B-subunit and heat-labile toxin (LT) B'-subunit from a mutant strain Escherichia coli were given to the rats in order to know the onset mechanism of toxin uptake. It seems likely that the toxin receptor, GM1 ganglioside, participates in the initiation of CT-uptake mechanism. A possible role of the intestinal ML cells was discussed.

Long-lasting functional unresponsiveness induced by a milk-transmitted Mls-1a-like superantigen

We have recently shown (Piazzon et al. (1994) J. Immunol. 153, 1553) that foster-nursing of BALB/c mice on F1 Mls-1bxa mothers induce the progressive deletion of V beta 6+ and 8.1+ T cells in 50% of the mice. Preceding clonal deletion, a state of functional inactivation of CD4+ T cells to Mls-1a and anti-V beta 6 antibodies was detected in young mice. In the present paper we show that foster-nursing of BALB/c mice on (BALB/cxAKR)FI mothers is able to induce alterations in T cell reactivity in the non-deletor mice. Lymph node cells from foster-nursed mice show a decreased proliferative level against anti-V beta 6 antibodies and a diminished response in MLR and in CTL assays. The proliferative responses to either OVA or Con-A are also reduced. This state of functional inactivation is detected even in 6-month-old foster-nursed mice. Thus, the transmission through milk of the Mls-1a-like superantigen correlates in the non-deletor mice with a long-lasting state of functional inactivation and a decreased immune reactivity.

Immunologic memory is established in nursling rats immunized with tetanus toxoid, but is not affected by concurrent supplementation with vitamin A

Experiments were conducted to determine whether nursling rats immunized with tetanus toxoid (TT) are able to produce a specific antibody response and whether oral treatment with retinyl palmitate, concurrent with immunization, affects the magnitude of the anti-TT response. When rats aged 8-15 d and nursed by vitamin A-sufficient dams were immunized with TT, no primary anti-TT immunoglobulin (Ig) M or IgG response was detected. However, nursling rats formed immunologic memory to TT because, when they were reimmunized at 40 d of age, their secondary anti-TT IgG response exceeded the primary response of 40-d-old vitamin A-sufficient rats (P < 0.02). Provision of retinyl palmitate (equal to 37.5 or 150 micrograms retinol equivalents) by mouth with early primary immunization did not change the magnitude of the secondary anti-TT IgG response. However, the age of nursling rats at first immunization significantly affected the magnitude of their secondary anti-TT IgG response, because rats first immunized at 15 d of age and reimmunized at 40 d of age produced a secondary response that was nearly fivefold greater than that of rats immunized at 8 and 40 d of age. In conclusion, nursling rats immunized with TT formed immunologic memory, which was affected significantly by the timing of the primary immunization. However, the administration of retinyl palmitate concurrent with early primary immunization did not significantly affect the development of memory to TT.

Cellular immune responses of pigs after primary inoculation with porcine respiratory coronavirus or transmissible gastroenteritis virus and challenge with transmissible gastroenteritis virus

The contribution of cell-mediated immunity to protective immunity against virulent transmissible gastroenteritis virus (TGEV) infection conferred by primary porcine respiratory coronavirus (PRCV) or TGEV exposure was assessed in pigs that were challenged with TGEV 24 days after a primary oronasal inoculation with PRCV or TGEV when 11 days old. PRCV exposure induced partial protection against TGEV challenge in suckling pigs based upon a decreased number of diarrhea cases (42% vs. 90% in age-matched control pigs), limited virus shedding in feces, and increases in virus-neutralizing serum antibody titers; in contrast, all 11-day-old pigs inoculated with TGEV were completely protected after challenge. Weaned pigs were also studied to eliminate any possibility that lactogenic immunity from contact PRCV-exposed sows contributed to protection against TGEV. Once weaned, none of the PRCV-exposed or age-matched control pigs had diarrhea after TGEV challenge; moreover, both groups exhibited less rectal virus shedding than suckling pigs. Vigorous lymphocyte proliferative responses (> 96,000 counts per minute (cpm)) were detected in mononuclear cells prepared from mesenteric (MLN) and bronchial (BLN) lymph nodes of TGEV-primed pigs. Analyses of these responses indicate that virus-specific cell-mediated immune responses correlated with protection against rectal and nasal virus shedding after TGEV challenge. Primary inoculation of 11-day-old pigs with PRCV induced moderate, transient virus-specific lymphocyte proliferation (> 47,000 cpm) in MLN from both suckling and weaned pigs after TGEV challenge. Substantial BLN proliferative responses (> 80,000 cpm) correlated with failure to detect TGEV in nasal secretions from these pigs. Virus-specific lymphocyte proliferation in spleens was delayed in onset and of lower magnitude than that observed in MLN and BLN. Virulent TGEV exposure resulted in increased percentages of T cell subsets, especially in the lamina propria and MLN, mucosa-associated lymphoid tissues in proximity to the primary replication site of TGEV in the small intestine. Our results confirm that PRCV infection primes anti-viral immune responses and, thus, contributes to partial immunity against virulent TGEV challenge.

Role of maternal antibody in the induction of virus specific and bystander IgA responses in Peyer's patches of suckling mice

Reciprocal crossings of C.B17 scid/scid and congenic BALB/c (+/+) mice generate genetically identical, immunocompetent F1 scid/+ mice that develop in either the absence or influence of passively transferred maternal immunity. By exchanging F1 scid/+ litters at birth among scid/scid, non-immune or reovirus immune BALB/c mothers we examined the relative ability of placental or colostral/milk transfer of virus specific maternal antibodies to interfere with reovirus immunization of the neonatal gut associated lymphoid tissues (GALT). Our data demonstrate that the Peyer's patches (PP) in 10-day-old mice are competent to support thymus dependent responses to acute reovirus stimulation that include the rapid (within 3 days) development of specific IgA plasma cells and the subsequent initiation of PP germinal center reactions. These neonatal mucosal immune responses occur independently of coincident specific maternal immune responses as evidenced by the identity of the reovirus specific responses engendered in F1 scid/+ pups of scid/scid versus +/+ mothers. However, transfer of pre-existing reovirus specific maternal antibody in milk via nursing on a reovirus immune (foster) mother completely abrogated reovirus specific neonatal IgA responses; while placental transfer of specific maternal antibody alone did not interfere with the immunization of the neonatal GALT with enteric reovirus. Reovirus challenge of 10-day-old mice was associated with a substantial bystander IgA response. Possible mechanisms responsible for the induction of the observed bystander IgA responses are discussed.

Serum immunoglobulin G concentration in goat kids fed colostrum or a colostrum substitute

To determine the suitability of a new colostrum substitute derived from goat serum and to determine the amount of colostral IgG needed to achieve serum IgG concentration > 800 mg/dl, twin kids from 14 does were fed colostrum or a colostrum substitute. The volume of colostrum or colostrum substitute fed was calculated so that half the kids in each group received IgG at a low dosage (1.5 g/kg of body weight) and the other half received IgG at a high dosage (3 g/kg). Kids were bottle fed the colostrum or colostrum substitute and then fed pooled goat's milk until 18 hours old, at which time they were allowed to nurse their dams. Does were milked manually every 2 hours after parturition until specific gravity of mammary secretions was < 1.02, the specific gravity of goat's milk. Serum IgG concentration of each kid was determined by means of single radial immunodiffusion at birth and 12, 18, and 24 hours and 7, 21, and 42 days after birth. Kids were weighed at each blood collection and monitored for illness daily. None of the kids had measurable serum IgG concentrations at birth. Mean serum IgG concentration was significantly higher in kids fed colostrum than in kids fed colostrum substitute at all times, except days 7 and 42 (P < 0.05). By 24 hours after birth, serum IgG concentration was > 800 mg/dl in all kids fed colostrum, in 4 of 7 kids fed the substitute at the higher dosage, and in 2 of 7 kids fed the substitute at the lower dosage.(ABSTRACT TRUNCATED AT 250 WORDS)

Impairment of B and T cell maturation in gut associated lymphoid tissues due to malnutrition during lactation

Previously we found that malnutrition during lactation in rats produces an impairment in the immune response to cholera toxin. In this report we found that malnutrition during lactation provokes in 28-day-old rats an increase of Thy1+ c mu+ cells in gut associated lymphoid tissues concomitantly with a decrease of sIgA+ B cells. No differences were found in the percentages of the IgM+ B cell populations. Furthermore, no differences were found in the Peyer's patch (PP) and mesenteric lymph node (MLN) T cell subsets in weaning rats when compared to controls. However, after 1 week of refeeding a higher percentage of the Thy1+ c mu- subset together with a lower percentage of CD5+, CD4+, and CD8+ T cells, were found in malnourished rats when compared to controls. The above results may indicate that B-cell maturation is delayed in malnourished rats at two stages of differentiation: (a) in the passage of pre-B cells (Thy1+ c mu+) to immature B cells (s mu+), and (b) in the switch from s mu+ B cells to s alpha+ B cells. The decrease of CD5+, CD4+, and CD8+ T cells together with an increase of the Thy1+ c mu- subset in gut-associated lymphoid tissues (GALT) may indicate that T-cell maturation is also delayed. Results obtained at weaning may be due to an engraftment by maternal milk-derived lymphocytes in the pups.

Deficient induction of the immune response to oral immunization with cholera toxin in malnourished rats during suckling

Malnourished rats during suckling were orally immunized with cholera toxin (CT) after different periods of refeeding. Intestinal fluids, sera, and supernatant fluids from cultured mesenteric lymph node (MLN) cells were obtained after rats were given three doses of CT and analyzed by enzyme-linked immunosorbent assay (ELISA) to evaluate the specific antibody response. Serum-specific immunoglobulin G (IgG), IgA, and IgM were severely diminished in malnourished rats immunized with three doses of CT after 1 week of refeeding when compared with those of controls. Also, a decreased IgA ELISA titer of the intestinal fluids and abrogation of the capacity to neutralize the CT in the intestinal ligated loop test were found. When a booster was given at 113 days of age, the immune response continued to be affected in the serum and the intestinal fluid. The results from the analysis of the supernatant fluids from cultured MLN cells were coincident with those mentioned above. When one dose of CT was administered into Peyer's patches (PP) after 1 week of refeeding, an impaired immune response was found in the intestinal fluid of malnourished rats during suckling compared with that of controls. This result together with the analysis of supernatant from MLN and PP cell cultures suggests that antigen triggering in the PP was affected. When the refeeding period was extended to 30 days and then the first dose of CT was administered, the antibody immune responses in intestinal fluid serum and supernatant fluid approached control values. These observations reinforce the fact that the gut-associated lymphoid tissue immaturity of the rats when they received the first CT dose (at 28 days old) was the main reason for the decreased immune response observed in the experimental group.

Effects of dietary alkylglycerols in lactating rats on immune responses in pups

Alkylglycerols (AG) are glyceryl ether lipid and are present in human and cow's milk and the hematopoietic organs such as bone marrow, spleen, and liver. The biologic effects of AG include stimulation of blood leukocyte and thrombocyte production and activation of macrophage and anti-tumor activity. The present study was conducted to determine the effects of dietary AG in lactating rats on AG levels in milk and development of certain immune responses in the pups. Lactating rats were fed diets supplemented with various levels of AG. Milk samples were expressed from the dams and blood was collected from the pups on postpartum d 8, 16, and 24. Concentrations of AG in milk from the dams fed AG were significantly greater than those of the controls (p < 0.05). Peripheral blood granulocytes were significantly elevated in pups from the dams fed AG, but there were no differences in peripheral blood lymphocyte numbers. Plasma levels of immunoglobulins were significantly greater for IgG (p < 0.01) and IgM (p < 0.001) in pups from the dams fed AG than in the control pups. The supplementation of AG in the diets of lactating dams significantly elevated AG levels in the milk, and the increased AG in the milk subsequently stimulated certain immune responses in the pups.

Transmission of an Mls-1a-like superantigen to BALB/c mice by foster-nursing on F1 Mls-1bxa mothers. Sex-influenced onset of clonal deletion

Foster nursing of BALB/c (Mls-1b) mice on (BALB/cxAKR/J)F1 and (BALB/cxDBA/2)F1 (Mls-1bxa), but not on (BALB/cxC57Bl/6)F1 or (BALB/cxC3H/He)F1 (Mls-1bxb mothers, induced the progressive deletion of V beta 6+ and V beta 8.1+ T cells in 50% of the litter. The onset of this Mls-1a-like clonal deletion was markedly sex-influenced, being earlier in females (8-10 wk of age) than in males (32 wk). In both sexes, CD4+ V beta 6+ cells were more affected than CD8+ V beta 6+ cells. Decreases in the percentage of V beta 6+ cells were detected simultaneously in the thymus, lymph nodes, and peripheral blood. Preceding clonal deletion, functional unresponsiveness of CD4+ T cells to Mls-1 a Ags and to anti-V beta 6 Abs could be detected in most young male and female mice. The transmission of the Mls-1a-like superantigen through foster-nursing on (BALB/cxAKR/J)F1 mice correlated with the presence in milk of the mouse mammary tumor virus envelope protein gp52.

Feline immunodeficiency virus can be experimentally transmitted via milk during acute maternal infection

Postnatal transmission of feline immunodeficiency virus (FIV) in neonates nursed by acutely infected mothers and infection resulting from oral inoculation of kittens with FIV were evaluated. Ten of 16 kittens nursed by four queens with FIV infection established immediately postpartum developed FIV infection. Five of 11 neonates orally administered cell-free FIV culture supernatant developed FIV infection. Kittens that developed FIV infection had greater proportions of CD4+ and Pan-T+ lymphocytes at birth than negative kittens. Infectious virus was recovered from the milk of acutely infected mothers. We conclude that FIV may be experimentally transmitted via milk from queens with acute infections and that oral administration of FIV to neonatal kittens results in infection.

Maternal transfer of infectious mouse mammary tumor retroviruses does not depend on clonal deletion of superantigen-reactive V beta 14+ T cells

Female C3H/HeJ mice maternally transmit through their milk an infectious mouse mammary tumor retrovirus (MMTV) which causes clonal deletion of T cell receptor (TcR)V beta 14+ T cells reactive to the retroviral superantigen (SAG). To test whether CD4+ or CD8+ T cells are crucial for intestinal infection and maternal transfer of exogenous retroviruses, newborn mice lacking CD4 or CD8 molecules after gene targetting were raised by surrogate C3H/HeJ mothers. In CD8-/- mice, clonal deletion of TcRV beta 14+ cells reactive to the SAG from this exogenous MMTV occurred with delayed kinetics. Deletion of TcRV beta 14+ cells was not observed in CD4-/- mice up to 12 months after exposure to the retrovirus. In both CD4-/- and CD8-/- mice TcRV beta 5+ and TcRV beta 11+ T cells were deleted in the presence of genomically integrated endogenous MMTV (Mtv), indicating that the lack of SAG-induced clonal deletion was not due to a general defect in these mutant mouse strains. Although TcRV beta 14+ T cells were not deleted in CD4-/- mice, female CD4-/- mice nursed on C3H/HeJ milk maternally transmitted the retrovirus to their offspring, albeit with delayed kinetics. These data demonstrate that CD4+ and CD8+ lymphocytes influence clonal deletion events and that the mechanisms responsible for clonal deletion of SAG-reactive TcRV beta 14+ T cells may be different from mechanisms which allow the mammary tumor virus to enter the mammary gland and complete its infectious cycle.

The influence of maternal separation on humoral and cellular immunity in farmed deer

The effect of maternal separation on in vivo and in vitro immune parameters was studied in young hybrid deer. Groups of fawns separated from their mothers either 2 days prior to or 7 days post immunization with keyhole limpet hemocyanin were compared with a control group of immunized, unseparated fawns. Animals separated prior to antigenic challenge had significantly higher concentrations of antigen-specific IgG in their serum than control animals. There was no influence on the humoral immune response in animals separated following immunization. In contrast, Con A transformations were transiently depressed in separated animals compared to the control group. The time separation was imposed relative to challenge and therefore influenced the subsequent immune response.

Hormonal control of intestinal Fc receptor gene expression and immunoglobulin transport in suckling rats

Hormonal control of immunoglobulin (Ig) absorption and of intestinal Fc receptor mRNA expression were investigated in rats to assess its potential role in the normal postsuckling inhibition of this transport system. Corticosterone and L-thyroxine therapy caused premature inhibition of the absorption of orally administered murine monoclonal antibody and of Fc receptor mRNA expression in a dose- and time-dependent manner. Low-dose corticosterone had no effect on Fc receptor mRNA synthesis after 3 d but decreased Ig transport fivefold after 7 d. High dose corticosterone resulted in a threefold reduction in Fc receptor after 3 d, and there was almost complete inhibition (> 30-fold) of transport and of Fc receptor transcript levels after 7 d. Similarly, 7 d of high-dose thyroxine decreased both serum Ig transport and Fc receptor (> 30-fold). However, adrenalectomy did not prevent the normal post-suckling declines in Ig transport or receptor synthesis. This study demonstrates that exogenous corticosteroids and thyroxine hormone inhibit Ig transport and steady-state duodenal Fc receptor mRNA levels in suckling rats. Endogenous adrenal steroids however, do not appear to be entirely responsible for the age-dependent decline in this transport system.

Regulation of parental alloreactivity by reciprocal F1 hybrids. The role of lactation

Adult reciprocal F1 hybrids differ in their susceptibility to parental graft versus host (GvH) reactions. These reactions were lower when the donor strain was syngeneic with the maternal one. Splenocytes from the member of the reciprocal pair in which the GvH reactions were lower also induced a decreased response of parental cells in cytotoxicity assays and in mixed lymphocyte reactions (MLR). The treatment with anti-CD8 plus complement was able to abrogate the different stimulatory ability of the reciprocal F1 spleen populations. Foster-nursing of F1 hybrids on mothers from the paternal strain was able to induce permanent alterations in the ability of their splenocytes to induce both parental anti-F1 MLR and CTL. The stimulatory ability was indistinguishable from that observed in the reciprocal F1 combination nursed on its own mother. Moreover, lactation was able to alter the ability of CD8+ spleen cells to regulate CTL and parental anti-F1 MLR. The results reported herein show the existence of a maternal effect acting though milk capable of altering the regulation of parental alloreactive T reactions towards self histocompatibility antigens.

Stimulation of natural killer cell numbers but not function in leukemic infant mice: a system primed in infancy allows survival in adulthood

Infant mice (< 3-4 weeks) demonstrate no detectable natural killer (NK)-cell-mediated immunity. The aim of the present work was to assess, quantitatively and functionally, the possibility that prostaglandin E2, (PGE2), an NK cell inhibitor, may be responsible for the absence of NK-cell-mediated activity in normal and/or erythroleukemia-bearing infant DBA/2 mice prior to the normal age-related onset of NK-cell-mediated lytic capacity. Infants (7 days after birth) were exposed daily to indomethacin via intraperitoneal injection for 10 days and/or recombinant interleukin-2 (rIL-2) daily for 4 days. Significant increases in the number of NK cells in both the spleen and bone marrow were found after 10 days of indomethacin or 4 days of rIL-2 in normal mice. The spleens but not the bone marrow of infants treated with indomethacin from tumor onset (7 days after birth) contained significantly more NK cells 10 days later than did control (tumor+vehicle) infants. Infants treated with rIL-2 during the last 4 days of tumor bearing, i.e., days 13-16 after birth, contained significantly more NK cells in both their spleen and bone marrow, while combined administration of rIL-2 and indomethacin to tumor-bearing, but not normal, infants resulted in a more than additive increase in the NK cell numbers in both organs relative to control (tumor+vehicle or vehicle alone). However, in neither normal nor tumor-bearing infants, could indomethacin, rIL-2, or a combination of both, induce the development of NK-cell-mediated functional (lytic) activity in spite of the generation, in nearly all instances, of high levels of NK cells in the presence of these agents. The observations collectively suggest that the lack of functional (lytic) reactivity of infant-source NK cells, in the presence of agents which potently enhance adult-source NK cells, reflects (1) the innate immaturity of infant NK lineage cells, or (2) the presence in infant NK-cell-containing organs of a function-suppressive mechanism which is indomethacin insensitive, i.e., not PGE2-mediated. The significantly prolonged survival, and even cure, of infant leukemic mice treated with indomethacin and/or rIL-2 may result from the agent-mediated elevated levels of precursor NK cells coming under the influence of some age-related, as yet unidentified, endogenous factor imbuing them with functional capacity.

Immune function in free-ranging harbor seal (Phoca vitulina) mothers and their pups during lactation

Immune function in harbor seal mothers and their pups during lactation was studied on Sable Island, Nova Scotia, Canada, during the springs of 1989 and 1990. Methods included total white blood cell and differential counts, a Protein A enzyme linked immunosorbent assay (ELISA) for total immunoglobulin G (IgG) quantification, and functionality testing of lymphocytes in vitro using the T-cell mitogen concanavalin A (ConA). Lymphocyte functionality and total IgG levels were reduced in the mothers at the end of lactation, suggesting a reduction in immune function, possibly as a result of the stress of fasting, or hormonal changes associated with lactation and estrus. By contrast, lymphocyte functionality and total IgG levels in pups were low at birth and higher at the end of lactation. Pups at birth and females late in lactation may therefore be more susceptible to infection by viral and bacterial agents. This study represents the first broad examination of immune function in a free-ranging pinniped population.

Influence of bromocriptine administration to mothers on the development of pup thymocyte and splenocyte subsets and on mitogen-induced proliferation in the mouse

The influence of prolactin (PRL) on the development of the immune system in the mouse was studied by injecting mothers with bromocriptine (CB-154) to produce hypoprolactinemic milk. Alterations in pup thymocyte and splenocyte cell subsets were observed to graded doses of CB-154 administered to mothers. There was an increase in the relative percentages of neonate thymic CD4 and CD8 cells at 5 days of age when mothers were injected with 100 micrograms of CB-154 2 x daily from day 1 to 5 of lactation, however, there was no alteration in absolute thymic subset cell numbers. The relative percentage of pup spleen CD4, CD8 and B cells were increased when mothers were administered 50 or 100 micrograms of CB-154 and the 50 micrograms dose resulted in a significant increase in the absolute number of CD4 cells while the 100 micrograms dose induced a significant decrease in the three splenic cell subsets examined. Graded doses of CB-154 administered to mothers resulted in decreases in the PRL concentration of stomach milk as measured by the Nb2 cell proliferation assay. The serum PRL level of the pups, however, was not altered by any dose of CB-154 injected to the mothers. The administration of PRL to pups nursing mothers given the 100 micrograms dose of CB-154 did not alter the pup thymocyte and splenocyte subset population from that of litter-mate controls. The administration of mouse PRL and mouse growth hormone antisera to pups nursing saline-injected mothers did not alter thymocyte and splenocyte subsets from that of saline-injected litter mate controls. The proliferation of neonatal thymocytes by Con-A stimulation was not altered by CB-154 injection to mothers and PRL administration to pups. However, since the percentage of thymic CD4 and CD8 cells in the thymus was increased 2 to 3 fold, the apparent lack of effect was in fact a decrease in the responsiveness of the thymocytes. Con-A stimulation of neonatal splenocytes resulted in a significant increase in proliferation for mothers administered CB-154 in keeping with the increase relative percentage of CD4 and CD8 cells observed. Prolactin administration to the pups did not alter the response. LPS stimulation of neonatal splenocytes increased the proliferation of B cells taken from pup nursing mothers administered CB-154 and PRL administration appeared to partially block this proliferation.(ABSTRACT TRUNCATED AT 400 WORDS)

Vaccines for preventing enterotoxigenic Escherichia coli infections in farm animals

Fimbrial vaccines are routinely given parenterally to pregnant cattle, sheep and swine to protect suckling newborn calves, lambs and pigs against enterotoxigenic Escherichia coli (ETEC) infections. Such vaccines are practical and effective because (1) most fatal ETEC infections in farm animals occur in the early neonatal period when the antibody titres in colostrum and milk are highest; (2) more than 90% of the ETEC in farm animals belong to a small family of fimbrial antigen types; (3) fimbriae consist of good protein antigens on the bacterial surface where they are readily accessible to antibody; (4) fimbriae are required for a critical step (adhesion-colonization) early in the pathogenesis of the disease. ETEC infections continue to be a significant clinical problem in farm animals in spite of extensive use of fimbriae-based vaccines. Definitive data on the efficacy of the commercial vaccines in field use are not available. The prevailing perception among animal health professionals is that the vaccines are effective, that the problem occurs chiefly among non-vaccinated animals, and that in some herds vaccination moves peak prevalence of disease from the first to the second or third week after birth, when mortality is lower. It has been suggested that extensive use of vaccines will rapidly select for the emergence of novel or previously low prevalence fimbrial antigen types. There is no evidence that this has happened after a decade of routine vaccine use in the United States. However, there is no active direct surveillance for such emergence.(ABSTRACT TRUNCATED AT 250 WORDS)

Epitope specificity of protective lactogenic immunity against swine transmissible gastroenteritis virus

The epitope specificity of the protective immune response against swine transmissible gastroenteritis (TGE) has been investigated by using circulating and secretory antibodies. This study was carried out with sows vaccinated with TGEV or the antigenically related porcine respiratory coronavirus (PRCV). TGEV vaccination of sows resulted in greater lactogenic protection of suckling piglets against TGEV challenge and a higher secretory immune response than PRCV vaccination did. These differences in the immune response were conditioned by the route of antigen presentation as a result of the different tropism of each virus. Epitopes on S protein, and in particular those contained in its antigenic site. A, were more immunogenic than epitopes on N and M proteins in both groups of vaccinated sows, as determined by a competitive radioimmunoassay. Minor differences in antibody response against the previously defined antigenic subsites Aa, Ab, and Ac were also detected, with subsite Ab being the most antigenic in both TGEV- and PRCV-immune sows. These findings suggest that antigenic site A on S protein, involved in virus neutralization, is the immunodominant site in pregnant sows that confer lactogenic protection. They also validate, in experiments with secretory antibodies, the antigenic maps made with murine monoclonal antibodies. Therefore, this antigenic site should be considered for vaccine or diagnostic development.

Eradication of hantavirus infection among laboratory rats by application of caesarian section and a foster mother technique

Hantavirus antibodies were demonstrated by the indirect immunofluorescent antibody assay, in the serum of inbred strains of laboratory rats, during the period 1973-1982, at the Unit of Experimental Immunology in the Catholic University of Louvain, Brussels, Belgium. LOU rats, as well as immunocytomas, which were requested by laboratories in the U.K. and The Netherlands, were supplied at a time when the infection was unknown and unsuspected in Europe. Hantavirus-infected laboratory rats were rendered free of virus through re-derivation by caesarian section and suckling by virus-free foster mothers. Immunocytomas were tested for the presence of hantaviruses by implantation into seronegative laboratory rats. The strain of hantavirus causing the laboratory infection was clearly different from the one circulating in free-living bankvoles in Belgium. The exchange of laboratory rats and rat tumours in relation to the potential risk of laboratory-acquired hantavirus infection, is discussed.

Factors that influence passive transfer of immunoglobulins in foals

Effects of farm management, breed, mare age, gestation duration, and climatologic factors on colostral specific gravity, colostral IgG concentration, and foal serum IgG concentration were evaluated. Climatologic variables measured were daily maximal, minimal, and mean air temperature, precipitation, average relative humidity, and total solar radiation. Presuckle, postpartum colostrum samples were collected from 140 Standardbred, 94 Thoroughbred, and 59 Arabian mares from January through June during 1985 and 1986. Thoroughbred (farm A, n = 61; farm B, n = 33) and Arabian (farm C, n = 45; farm D, n = 14) mares were located in Ocala, Fla; Standardbred mares (farm E) were in Montgomery, NY. Mares from farms A, B, D, and E foaled in box stalls, and mares from farm C foaled in sand paddocks. Mares with premature lactation greater than 12 hours were not included in the study. Foals were clinically normal at birth and suckled colostrum without assistance within 2 hours of parturition. Specific gravity of presuckle colostrum samples was measured by use of an equine colostrometer. Blood samples were collected 18 hours after parturition from 253 of the 293 foals (n = 45, 25, 32, 13, 138 on farms A through E, respectively) to determine serum concentration of IgG. The IgG concentrations in colostrum and serum were measured by single radial immunodiffusion. Data were analyzed by multiple regression or chi 2 analysis. The most important determinants of foal serum IgG concentration were the IgG content and specific gravity of presuckle colostrum samples (P less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Transfer of T-cell mediated immunity to Hymenolepis nana from mother mice to their neonates

Administration of lymph node cells from Hymenolepis nana-infected mice into lactating mothers, or directly suckling neonates successfully transferred immunity to the neonates. The capacity of lymph node cells to transfer immunity was completely abrogated by pretreatment with anti-Thy-1.2 monoclonal antibody and complement.

The importance of udder and teat conformation for teat seeking by the newborn calf

Because antibody levels in colostrum and the efficiency of the intestinal absorption of these antibodies decrease with time after birth, late sucking inadequate passive immunity. The influence of the conformation and the size of the udder and teats of the dam on the teat-seeking behavior of newborn calves with respect to the time they first suckle was studied in 42 cow-calf pairs housed in individual calving pens. A smaller distance from udder to floor (e.g., low slung udders) led to increase in the time spent teat seeking; it also had a significant effect of the time of the first suckle. The variation in the distance from udder to floor accounted for 24 and 15% of the variations in rank order of the calves with respect to duration of active teat seeking before first suckling and to the time to first suckle, respectively. The results of this study showed that calves born to cows or heifers with low slung udders cannot be expected to obtain colostrum soon enough by natural suckling. They should either be helped to suckle or be hand fed to ensure that they receive a good and adequate passive immunity.

Serum immunoglobulin concentrations in genetically different types of suckling beef calves in a tropical environment

Factors influencing the serum concentrations of gamma-globulin (gamma-G) during the neonatal period were studied in Shorthorn x Hereford (SH), Africander x SH and Brahman x SH calves born to cows grazing in a tropical environment. There were no significant effects of age of dam, sex or breed of calf on the gamma-G concentrations of calves from birth to 48 hours of age. Concentrations of gamma-G fell within two ranges: group A, 10 to 20 g/l and group B, 35 to 70 g/l. The number of calves in each group was not significantly different between breeds and overall 30% of calves were in group A. Body weight gain from birth to 10-day-old was greater (P less than 0.01) in calves in group B than in group A. Plasma cholesterol concentrations in 10-day-old calves were higher in group B than in group A calves supporting the interpretation that group B calves had higher milk intakes. Identification of calves receiving adequate amounts of colostrum has fundamental significance for the efficient production of cattle in the tropics.

Cow-calf behaviour in relation to first suckling

For the newborn calf, the length of time between birth and when (and if) it manages to obtain its first suckle plays an important role in the acquisition of passive immunity. In a study of 21 pairs of dairy cows and their calves, loose housed in individual calving boxes, the calves suckled for the first time at a median of four hours, nine minutes after birth. Nineteen suckled within 12 hours, with a range between 50 minutes and 11 hours, 44 minutes. Calves that were active early usually suckled early. However, irrespective of the start of a calf's activities, long pauses while teat seeking played a decisive role in the time of the first suckling. Factors which affected the periodicity and length of these pauses would therefore greatly influence the time of the first suckling.

Effect of vitamin E and fat source in sows' diets on immune response of suckling and weaned piglets

Thirty-six 7-mo-old gilts were used to study the effects of dietary vitamin E and fat source (5% sunflower oil or animal fat) in pregnant and lactating sow diets on serum vitamin E concentration and on cell-mediated and humoral immune response in suckling and weaned piglets. Six gilts each received one of six diets throughout pregnancy and lactation. The basal diets (13 mg alpha-tocopherol/kg diet) were supplemented with dl-alpha-tocopheryl acetate to 48 and 136 mg alpha-tocopherol/kg of feed (average analyzed values). After weaning (at 4 wk of age) all pigs received identical diets (20 mg of alpha-tocopherol/kg feed). One week after weaning, pigs were immunized (i.m. with ovalbumin and tetanus toxoid) and antibody production was measured. Blood samples were taken immediately after birth, at 1 wk after birth, at weaning, and at four weekly intervals after weaning. Samples were analyzed for alpha-tocopherol concentration, total number of leukocytes, T- and B-lymphocytes, lymphocyte stimulation with concanavalin A, lysozyme activity, and immunoglobulin concentrations. It was concluded that a high vitamin E level in the sow's diet increased serum vitamin E concentration of 1-wk-old pigs (P less than .05). Immune response against ovalbumin was increased (P less than .05) at 1 wk of age after immunization for weaned pigs from sows fed the high level of vitamin E. Also, the phagocytic measures of pigs at 1 wk of age were increased by the medium vitamin E level (P less than .05). Fat sources in the sow's diet had no consistent effect on the immunological measures of pigs.

Suppression of lymphocyte blastogenesis by porcine interferon-alpha

Peripheral blood lymphocytes (PBL) from five four-day-old and five six-week-old piglets were treated with 10 to 320 units of porcine interferon-alpha, and their blastogenic responses to phytohaemagglutinin or pokeweed mitogen were compared with those of control lymphocytes. There was significant inhibition of the blastogenic response to phytohaemagglutinin by 320 units of interferon-alpha, and of the response to pokeweed mitogen by 320 and 160 units of interferon-alpha. Porcine interferon-beta was cytotoxic to porcine PBL. The blastogenic response to pokeweed mitogen was significantly higher in PBL from the younger piglets.

Brugia pahangi: circulating antibodies to adult worm antigens in uninfected progeny of homologously infected female jirds

Serum IgG antibody levels to adult Brugia pahangi antigens were measured in uninfected offspring from uninfected and B. pahangi-infected female jirds. Antibody titers to B. pahangi antigens in sera of offspring from infected females mimicked the maternal titer during the suckling period. Neonate titers peaked at 2 weeks of age at levels as high as 1:4100, then decreased to levels well below maternal titers by 8-12 weeks of age. Concurrent maternal and 2-week-old neonate sera recognized identical B. pahangi antigens in Western blots. Spleen cells from 2-week-old filariae-exposed and unexposed offspring failed to produce measurable antibody to B. pahangi in vitro. Progeny of uninfected mothers nursed by B. pahangi-infected females showed circulating IgG antibody titers to adult worm antigens similar to those of homologously reared offspring. Conversely, offspring born to B. pahangi-infected females and nursed by an uninfected female had no serum antibodies to B. pahangi antigens. Blastogenic responses of spleen cells to the mitogens phytohemagglutinin and pokeweed mitogen, and adult B. pahangi antigens, were not different between offspring groups. Mean areas of pulmonary granulomas induced by the intravenous inoculation of B. pahangi antigen-coated beads also did not differ between 4- and 8-week-old progeny of uninfected or infected females. These results suggest that the circulating IgG antibodies to adult B. pahangi antigens demonstrated in offspring of infected female jirds are maternally derived via the milk and do not alter the cellular responses of uninfected offspring to B. pahangi antigens as measured by antigen-stimulated blastogenesis or pulmonary granulomatous inflammatory response.

Antigen-independent selection of T15 idiotype during B-cell ontogeny in mice

Precursors of B cells capable of responding to a T-independent form of phosphorylcholine (PC) in splenic focus assays were detected in the spleens of neonatal mice as early as 4 days after birth. The earliest anti-PC B cells were T15-. T15+ foci-forming B cells were first detected 6 days after birth and expanded rapidly to constitute greater than 80% of the total PC-specific foci by day 10. Injection of heat-killed S. pneumoniae (R36A) into neonatal mice resulted in priming of the antibody response to PC, with an idiotype profile reflecting that of precursors of foci-forming B cells at the time of antigen administration. Priming of 2-day-old mice with 2 x 10(6) and 2 x 10(7) R36A induced a five- and ten-fold increase in the antibody response to phosphorylcholine 6 to 8 weeks later. However, only 10 to 15% of the serum antibodies expressed the normally dominant T15 idiotype. Doses below 2 x 10(5) R36A showed no detectable priming activity. PC-specific hybridomas derived from mice injected with 2 x 10(7) R36A 2 days after birth lacked the idiotypic and molecular characteristics typical of T15+ antibodies. Antibodies to phosphorylcholine, raised by immunization of 6-week-old mice are normally protective against pneumococcal infection. However, serum antibodies from mice treated with R36A 2 days after birth and responding to phosphorylcholine following challenge with R36A at 6 weeks of age failed to protect against deliberate infection with virulent S. pneumoniae. These observations imply that the antigen phosphorylcholine does not play a role in the selective expansion and dominant expression of the T15 idiotype.

Inhibition of offspring response to HEL-CFA by administration of anti-HEL MAB to the mother is not related to the predominant idiotype, IdXE, or specificity of the MAB

In the neonatal suckling mouse, the antibody response to HEL-CFA can be inhibited by administration of certain anti-HEL monoclonal antibodies to the mother. The murine primary response to hen egg-white lysozyme (HEL), which can be elicited in A/J mice as early as 7 days of age, is characterized by a predominant specificity that includes the 3 N-terminal amino acids of HEL (TIP-dependence) and by a predominant idiotype, IdXE. A panel of murine IgG1 anti-HEL mAbs was administered to the suckling offspring via the mother. These mAbs were not equivalent in their effects on the offspring. Only two of six IgG1 mAbs, 2F4/2E5 (IdXE-positive, TIP-dependent) and 2D1 (IdXE-negative, TIP-independent), consistently induced suppression of the response of A/J offspring when immunized at 16-20 days of age with HEL-CFA. Suppression averaged 71% for 2F4/2E5 and 74% for 2D1 and was always statistically significant (P less than .05) when 275 micrograms mAb was administered IP to the mother within 24 hr postpartum. Since 2D1 is IdXE-negative and TIP-independent, neither of these properties appears to be crucial for suppression. Differences in transfer of the mAbs from the mother to the offspring or differences in catabolism of the mAbs in the offspring were not detected. When various characteristics of the mAbs such as affinity, idiotypy, and fine specificity were considered, there was no single factor which determined suppression. One of the two mAbs that suppressed the offspring response, 2D1, is idiotypically highly connected in the anti-HEL mAb panel. This observation suggests that idiotypic interactions in the developing neonatal repertoire with subsequent perturbation of T and B cell repertoire development may be an area for future investigation.

The role of mucus in antibody-mediated rapid expulsion of Trichinella spiralis in suckling rats

Rat pups suckling dams parasitized by Trichinella spiralis express rapid expulsion, a protective response that is associated with the entrapment of infectious muscle larvae in intestinal mucus. Immunofluorescent studies revealed that antibodies were bound to the surfaces of the entrapped larvae. Mucus binding and rapid expulsion occurred in normal pups dosed with larvae coated with antibodies prepared from infected rat serum. Subsequent experiments revealed that entrapped larvae escaped from mucus after 2 hr in vitro incubation in saline. Escape correlated with the loss of the surface-bound antibodies, suggesting that mucus entrapment was reversible and dependent on antibody coating. Finally, when protective antibodies were injected 1, 2 or 6 hr after larvae were administered to pups, the parasites were forced to leave their epithelial niche and became enveloped in mucus. The above findings suggest that mucus trapping of T. spiralis larvae is dependent upon the coating of larvae by antibody, but that trapping is reversible, and is not in itself the pivotal event in rapid expulsion. The primary mechanism of rapid expulsion appears to be antibody-mediated inhibition of processes required for the parasite to maintain itself in the epithelium.

[Variations in the concentrations of the immunoglobulins IgG1, IgG2, IgM and IgA in sheep. 2. Changes in the blood of lambs of different breeds and crossbreeds during the course of the rearing period]

The sera of 188 lambs from seven breed groups were analyzed for the concentrations of IgG1, IgG2, IgM and IgA by radial immunodiffusion using monospecific antibodies. From each lamb, 14 blood samples were drawn before and 5 samples after weaning. The following results were obtained: 1. Immunoglobulins could not be detected in sera drawn before the first intake of colostrum. 2. In normally suckling lambs, the peak concentrations of maternal immunoglobulins are attained at 0-18 hrs after birth. They can be assessed in a single blood sample drawn between 18 and 24 hrs. 3. The half-life times of maternal immunoglobulin in lamb sera are 11 days for IgG1, 7 days for IgG2, 6 days for IgM and 18 hours for IgA. 4. The absolute peak heights relate to the amounts of colostrum ingested before 12-18 hrs after birth. 5. The decline of maternal immunoglobulins in lamb sera over-laps with the onset of lamb immunoglobulin synthesis. Renewed rises of concentrations are observed for IgG2 after week 2, for IgM after week 3 and for IgG1 after week 7. The concentrations of IgA remain at the low levels characteristic for the serum of grown sheep. 6. The role of immunoglobulin synthesis in suckling lambs is only briefly and to a small extent reduced after weaning.

In vitro modulating effects of porcine immunoglobulin G on mitogens-induced lymphocyte response in precolostral, suckling and weaned piglets

The influence of allogeneic IgG on in vitro reactivity of peripheral blood lymphocytes (PBL) of neonatal colostrum-deprived piglets as well as of suckling and weaned piglets was studied. PBL were preincubated with purified allogeneic IgG for 24 h before their ability to respond to PHA, Con A or PWM was tested. PBL of precolostral piglets pretreated with allogeneic IgG exhibited higher response to PHA (P less than 0.01) than untreated control cells. An increased response of PBL treated with IgG was also observed in suckling piglets as compared to their respective control cells (P less than 0.01). Responsiveness of PBL treated with IgG to PWM was suppressed. No differences in response to Con A regardless of the sources of lymphocytes was observed as compared to IgG untreated controls. The results suggest that pretreatment of lymphocytes of piglets with allogeneic IgG modulates their reactivity to mitogens, suppressing the response to PWM and stimulating the response to PHA, respectively.

High intravenous doses of human immune globulin suppress neonatal group B streptococcal immunity in rats

We evaluated the effect of intravenously administered immune globulin (IVIG) on neonatal group B streptococcal (GBS) infection in vivo and in vitro. A suckling rat model was used to compare the impact of penicillin (150 mg/kg) with albumin control, high-dose IVIG (2.7 gm/kg), or low-dose IVIG (0.68 gm/kg) on survival and bacteremia. Three lots of IVIG (two standard and one hyperimmune) with varying titers of GBS type III activity were used. An opsonophagocytic assay was then employed to evaluate in vitro the effect of concentrations of penicillin (none to 2.4 micrograms/ml), IVIG (none to 20 mg/ml), organism-specific (GBS type III-specific) activity (none to 1280(-1], and quantity of organisms (10(4) to 10(6] on the killing of several strains of GBS type III. Low doses of IVIG enhanced suckling rat survival (p less than 0.0025) and bacterial clearance (p less than 0.01). High doses of IVIG did not improve survival and in fact delayed bacterial clearance (p less than 0.05) when compared with low doses. Survival and bacterial clearance increased as the GBS type III activity of the IVIG lot increased. GBS opsonophagocytosis was suppressed at all penicillin concentrations (p less than 0.01) by high levels of IVIG (20 mg/ml). High-dose IVIG suppression of GBS opsonophagocytosis decreased as type III activity of the lot increased. We speculate that high doses of nonspecific IVIG may cause blockade of neutrophil or bacterial receptors necessary for GBS immunity in neonates.

Heterologous protection against invasive Escherichia coli K1 disease in newborn rats by maternal immunization with purified mannose-sensitive pili

Heterologous protection against Escherichia coli K1 bacteremia with antibody to purified mannose-sensitive (MS) pili was demonstrated in a neonatal rat model. The serological relatedness of purified MS pili from 17 E. coli K1 clinical isolates was examined by an enzyme-linked immunosorbent assay. Five pilus serogroups were identified, with the pili in each group showing 50% or greater cross-reactivity with the typing serum of the group. The MS pili from 12 of 17 (70%) strains belonged to just two serogroups. Pregnant Sprague-Dawley rats (dams) were immunized with purified pili, and their newborns (pups) were challenged with heterologous E. coli. Bacteremia was significantly reduced when the pili used for immunization were from the same serogroup as the pili expressed by the challenge bacteria. Thus, immunization with C94 pili and challenge with E03 (71% cross-reactivity) or E04 (50% cross-reactivity) resulted in bacteremia rates of 12 of 17 (17%) versus 51 of 79 (65%) in controls and 0 of 75 (0%) versus 28 of 70 (40%) in controls, respectively (P less than 0.001 for each comparison). With lower cross-reactivity, less protection was observed (P less than 0.05 for 22 to 37% pilus serological relatedness). No protection was seen in pups suckled by dams immunized with MS pili having only 5% serological relatedness to the pili on the challenge strain.

Effect of breast feeding on the development of anti-idiotype antibody response to F glycoprotein of respiratory syncytial virus in infant mice after post-partum maternal immunization

Groups of lactating BALB/c mice were immunized in the immediate postpartum period with high doses of mAb (Ab-1) to the F-glycoprotein (F-gp) of respiratory syncytial virus (RSV). This antibody possessed neutralizing activity against the whole virus. The immune response to F-gp was studied in the breast feeding infant mice of such mothers at regular intervals before and after weaning. All infant mice exhibited anti-F-gp activity in serum, which was detected until 6 wk of age. Splenic cells of such breast feeding infant mice collected after weaning exhibited in vitro synthesis of antibody against Ab-1, the antibody previously used for maternal immunization. Subsequent immunization with homologous purified RSV F-gp resulted in a booster response for IgG, IgM, and plaque-neutralizing antibody to the immunizing RSV protein and to the whole virus in the infants primed via breast feeding. The enhanced antibody response was specific for the antigenic epitopes of the virus protein recognized by the monoclonal antibody used for maternal immunization. Similar booster effect was seen in control infants of nonimmunized mothers who were immunized with a polyclonal Ab-2 prepared by repeated immunization with Ab-1 in DBA/2 mice. These data demonstrate induction of RSV-specific anti-idiotype antibody in the neonates via the process of breast feeding, secondary to maternal immunization after the delivery of the neonate. Use of idiotypic vaccines in the mother and the transfer of RSV-specific idiotypes may offer an alternate approach to the development of effective immunoprophylaxis for RSV infection in early infancy.

Effects of early antigen exposure through lactation on later specific antibody responses in mice

This study characterized totally the effects of early Ag exposure by the suckling route on later specific antibody responses. When mother mice of BALB/c or C57BL/6 strains were injected with deaggregated human gamma-globulin (HGG) immediately after delivery, total amounts of HGG in sera of offspring increased until 2 wk of age. The catabolism of transferred HGG was extremely slow and the half-life was about 3 wk in both strains. Hence, small amounts of Ag in mothers, 0.5 micrograms in C57BL/6 and 50 micrograms in BALB/c, could tolerize their offspring effectively. As these were minimum tolerogenic doses, the strain difference in ease of tolerance induction is apparent already during suckling. The study on timing dependent effects of HGG-specific antiserum on tolerance induction by mothers given 50 micrograms HGG demonstrated that the tolerance is achieved within the 1st wk of lactation in C57BL/6 offspring, but not in BALB/c offspring, and the restoration from the tolerance needs more than 6 wk under circumstances, supposedly, without free Ag. Whereas the tolerance was induced in a dose-dependent manner in each class of antibody, the dissociation of tolerant states between IgM, IgG, and IgE antibody classes was found in C57BL/6 offspring. It is interesting that C57BL/6 offspring were sensitized weakly, but significantly, by mothers given subtolerogenic doses. However, this was not apparent in BALB/c. Thus, the Ag dose and the animal strain are related closely to the consequences of this Ag exposure. The aging of suckling mice within the first 2 wk of life or immunomodulators administered early in life did not seriously affect the consequences. Studies on a cellular basis showed that the tolerance is caused by the selective defect in helper T cell function and the suppressor cell activity is not associated with the mechanisms. This contrasts with other models of oral tolerance.