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Biomedical subjects

J M Pollock

Publications and source records attributed to J M Pollock.

At least 73 records · Page 4Linked to original sources

Detection of Mycobacterium bovis infection in skin test-negative cattle with an assay for bovine interferon-gamma.

Mycobacterium bovis was isolated from respiratory secretions and lymph nodes from 15 skin test-negative cattle which exhibited interferon-gamma responses. These field cases, identified by blood testing, constituted a significant proportion of skin test-negative cattle which had been subjected to extensive post mortem examinations. Typical tuberculous lesions were found in seven of them. The consequences of cattle with early tuberculosis infection not being detected by traditional tuberculin testing are considered.

Animals↗

Effects of dietary vitamin E and selenium on in vitro cellular immune responses in cattle.

Four groups of calves depleted of alpha-tocopherol and selenium (Se) were supplemented with alpha-tocopherol or Se or alpha-tocopherol and Se or received no supplement. In vitro lymphocyte proliferative responses were measured in fetal calf serum (FCS), in autologous serum and in pooled sera from each group. In FCS, the responses to pokeweed mitogen were significantly enhanced for calves supplemented with alpha-tocopherol. In autologous serum, the mean responses to keyhole limpet haemocyanin (KLH) were greatest for calves supplemented with Se alone. In pooled sera from each group, lymphocytes from calves supplemented with Se alone showed enhanced responses to KLH in the presence of serum from calves supplemented with alpha-tocopherol. The calves depleted of alpha-tocopherol had increased circulating percentages of BoCD2 lymphocytes, apparently due to changes in the BoCD4 subpopulation. The percentages of B cells were greatest in calves supplemented with alpha-tocopherol and Se. The results indicate that alpha-tocopherol and Se have interactive effects on lymphocyte responses to antigen and suggest that micronutrient status is important when interpreting the results of in vitro assays of lymphocyte function.

Animals↗

Pathogenesis of Mycobacterium bovis infection in cattle.

This paper reviews the pathogenesis of Mycobacterium bovis infection in cattle, focusing on aspects relating to the host rather than the organism. A broad concept of pathogenesis has been considered and information is presented on sources and routes of infection, as well as the immune responses and pathology. In addition, data is presented on the excretion of M. bovis from tuberculous cattle.

Animals↗

Level of nutrition and age at weaning: effects on humoral immunity in young calves.

Thirty-two calves were studied to determine the effects of level of nutrition (400 and 1000 g (air-dry matter) milk substitute per d) and age at weaning (5, 9 and 13 weeks) on humoral immune responses measured in serum and bronchoalveolar washings (BAW). All calves were immunized with Keyhole limpet haemocyanin (KLH) at 3 weeks of age, and with horse erythrocytes (HRBC) 1 d after weaning. Feeding the higher level of nutrition compared with the lower level decreased anti-HRBC titres and serum IgG2 and IgA responses to KLH (P < 0.05). Weaning at 5 compared with 9 weeks of age decreased serum anti-HRBC responses (P < 0.05), but weaning age had no effect on anti-KLH responses (P > 0.05). Feeding the higher level of nutrition increased total protein (P < 0.05) and IgG2 concentrations (P < 0.01) in BAW. The results showed that variation in husbandry conditions that is within conventional limits affects humoral immune responses in young, artificially-reared calves.

Aging↗

Immunoblot analysis of humoral immune responses to Mycobacterium bovis in experimentally infected cattle: early recognition of a 26-kilodalton antigen.

Development of a serodiagnostic test for bovine tuberculosis necessitates an understanding of the humoral immune responses of animals following infection with Mycobacterium bovis. The antibody responses in groups of calves challenged intranasally with different doses of M. bovis (approximately 10(2), 10(4), and 10(6) CFU) or placed in contact with the infected animals were analyzed by immunoelectrophoretic blotting in which a whole-cell sonicate of M. bovis was utilized as an antigen. Antibody responses were evident early in infections in which calves were exposed to high doses of M. bovis, while in groups exposed to lower doses, the time until antibody was detected increased as the challenge dose decreased. In cattle exposed to M. bovis, immunoblot analysis showed antibody responses to three main antigens of 26, 22, and 16 kDa. It was further demonstrated that antibody responses to the 26-kDa antigen appeared earliest in the course of infection. Preliminary investigations in this study have identified a 26-kDa antigen for potential use in improved serodiagnosis by enzyme-linked immunosorbent assays.

Animals↗

Identification of bovine T-cell epitopes for three Mycobacterium bovis antigens: MPB70, 19,000 MW and MPB57.

Bovine tuberculosis remains a serious problem in several regions, partly due to a lack of specific diagnostic tests. The aim of this study was to identify bovine T-cell epitopes for defined Mycobacterium bovis antigens using an experimental model of the natural disease. Panels of synthetic peptides (16-mers with five residue overlaps) were produced from published amino acid sequences for MPB70, the 19,000 MW antigen and MPB57. In vitro lymphocyte proliferation assays were used to identify T-cell epitopes. Lymphocytes from experimentally infected cattle proliferated in response to five epitopes (residues 88-105 and 144-163 for MPB70; 1-16 and 67-84 for the 19,000 MW antigen; and 85-100 for MBP57). These epitopes were not recognized by control, non-infected animals, but were recognized by field reactors to intradermal tuberculin testing. All five epitopes were recognized by three different breeds of cattle (Friesian, Charolais and Simmental). In addition, the bovine T-cell epitopes identified for the 19,000 MW antigen in this study were similar to epitopes previously reported for man and mouse. Thus, as well as identifying candidate reagents for improved diagnostic tests and vaccination, this study provides evidence for genetic promiscuity T-cell recognition of major myobacterial epitopes.

Amino Acid Sequence↗

Fetomaternal hemorrhage following funipuncture: increase in severity of maternal red-cell alloimmunization.

OBJECTIVE: To determine the prevalence of fetomaternal transplacental hemorrhage after funipuncture and its effect on maternal red-cell alloantibody levels. METHODS: The prevalence and size of transplacental hemorrhages at the Health Sciences Centre were studied in two groups of patients: 174 women who were not alloimmunized or were carrying fetuses whose red cells were negative for the antigen to which they were immunized, and 122 women who were alloimmunized and carrying fetuses whose red cells were positive for the antigen to which they were immunized. In the alloimmunized group with affected fetuses, we surveyed the incidence of maternal antibody increase in titer by two or more doubling dilutions and the Rh(D) antibody increase (in microgram/mL of serum) of more than 50% after funipuncture. RESULTS: One hundred of the 174 women (57.5%) in the nonimmunized group and 69 of the 122 women (56.6%) in the immunized group had evidence of transplacental hemorrhages ranging in volume from 0.03 mL to greater than 5 mL of fetal red blood cells. In the latter group, antibody titer increases of 2 to 9 and doubling dilutions occurred in 37 of 74 women (50%) in whom such measurements were carried out. Increases of anti-D exceeding 50% occurred in 44 of 53 women (83%) in whom quantitative measurements were assayed. CONCLUSION: Funipuncture carries a high risk of fetal transplacental hemorrhage. In the immunized woman carrying an antigen-positive fetus, this will increase the level of her antibody and probably increase the severity of hemolytic disease in her fetus. In alloimmunized women, funipuncture should rarely be carried out to determine the fetal antigen status. Serial amniocenteses combined with careful serial ultrasound observation of the fetus are safer. Funipuncture should not be done in alloimmunized women before the cord vessels are of adequate size to allow immediate intravascular fetal transfusion, if required.

Blood Group Antigens↗

Alteration of cellular immune responses by nutrition and weaning in calves.

The effects of two levels of nutrition (400 g and 1000 g air dry matter milk substitute powder per day) and three ages of weaning (five, nine and 13 weeks) on cellular immune responses were determined in 32 calves. The lower level of nutrition was found to increase skin sensitivity responses to keyhole limpet haemocyanin (KLH) and decrease lymphocyte blastogenesis test (LBT) responses to ConA and pokewood mitogen (P < 0.05). Weaning at five weeks old resulted in increased KLH skin responses at nine weeks old compared with unweaned calves and decreased LBT responses to ConA and phyto-haemagglutinin at 10 weeks old compared with calves weaned at nine weeks old (P < 0.05). Weaning at five weeks old also increased peripheral blood concentrations of BoCD2+ and BoCD8+ lymphocytes (P < 0.05). The results show that the choice of husbandry conditions alters cellular immune responses in young calves and suggest that early weaning effects are essentially nutritional.

Age Factors↗

Effects of weaning on antibody responses in young calves.

Two experiments were performed to investigate the effects of cessation of feeding milk substitute (weaning) on antibody responses to Keyhole Limpet haemocyanin (KLH) in young calves. In the first experiment, 47 calves were weaned at 42 days of age, while a further 47 calves remained unweaned until 84 days of age. All calves were immunized with KLH at 43 and 85 days of age. Serum IgG1, IgG2 and IgA responses to KLH were increased in the early weaned calves compared with the late weaned calves following both primary and secondary immunizations. In the second experiment, 24 calves were immunized with KLH at 21 days of age. Subsequently, at 35 days of age, eight calves were weaned, eight calves were sham-weaned and eight calves remained unweaned. Sham-weaning involved continuing to feed milk substitute of greatly decreased nutritional value in an attempt to isolate nutritional from behavioural effects of weaning. No effects of treatments on antibody responses were detected. It was concluded that weaning affects antibody responses to antigens given near weaning but not to antigens given 2 weeks before weaning.

Aging↗

Severe anti-C hemolytic disease of the newborn.

OBJECTIVE: Because of referral of a C-alloimmunized pregnant woman with a previous hydropic death whose fetus survived after four intraperitoneal transfusions, prevalence and severity of anti-C hemolytic disease of the newborn were investigated. STUDY DESIGN: The numbers of C- or Ce-alloimmunized pregnancies in Manitoban women and their outcome for the 28-year period ending Oct. 31, 1990, were reviewed. The literature relating to C or Ce alloimmunization from 1944 to 1990 was surveyed. RESULTS: In Manitoba for the period reviewed there were 120 pregnancies in 80 C- or Ce-alloimmunized women. Twenty-two ended in abortion and two in fetal death unrelated to anti-C or anti-Ce. Of the remaining 96, 33 fetuses of 32 pregnancies were affected but only eight (6.7%) required treatment after birth. None were severely affected. In the literature there are only three other reported deaths from C or Ce hemolytic disease; two of the three may have been the same patient. The prevalence of C or Ce alloimmunization reported in various series, including our own, ranged from 8.7 to 185 per 100,000 pregnancies. CONCLUSIONS: Because on rare occasions, C or Ce alloimmunization can cause severe hemolytic disease, criteria for investigative measures such as amniocentesis or cordocentesis do not differ from the criteria for instituting these measures in Rho (D)-alloimmunized pregnancies.

Erythroblastosis, Fetal↗

Maternal Kell blood group alloimmunization.

BACKGROUND: Two recent paper have provided conflicting views regarding the severity of Kell hemolytic disease of the newborn. METHODS: We reviewed our experience during 1944-1990 with pregnant Kell-alloimmunized Manitoban women and similar women referred from outside of Manitoba. RESULTS: Between 1944-1990, 311 Kell-immunized Manitoban women had 459 pregnancies, of which 63 ended in abortion or stillbirth unrelated to anti-Kell. Of the infants born, 376 were unaffected and 20 were affected. Twelve did not require treatment; two needed phototherapy, one required a simple transfusion, and one an exchange transfusion. One died of kernicterus and three were hydropic and died; all four deaths occurred between 1948-1954. Fourteen Kell-immunized women with 16 pregnancies were referred from outside Manitoba. Eleven had a history of Kell hydropic fetuses and ten had hydropic fetuses at referral. Five of the hydropic fetuses survived and five died. Five women had Kell-negative infants correctly predicted by amniocentesis (two) and by fetal blood sampling (three). Serial amniotic fluid delta OD 450 readings were 83-89% accurate in predicting the presence and severity of Kell hemolytic disease. Life-threatening inaccuracies occurred, primarily in the early and middle second trimester. CONCLUSIONS: Kell hemolytic disease, although rare, may be as severe as Rh(D) hemolytic disease when it does occur. When there is a history of hydrops or the father is Kell-positive and the maternal anti-Kell indirect antiglobulin titer is 8 or greater, amniocentesis should be performed at 16-20 weeks' gestation. Fetal blood sampling followed by fetal intravascular transfusion is indicated if delta OD 450 readings approach the 65% level in modified zone 2 of Liley or if amniocentesis is precluded because of an anterior placenta and there is a history of hydrops or ultrasound evidence of fetal hemolytic disease.

Amniotic Fluid↗

Estimation of immunity in the developing calf: cellular and humoral responses to keyhole limpet haemocyanin.

The efficacy of keyhole limpet haemocyanin (KLH) as a test antigen was determined in calves. Humoral and cellular (in vivo and in vitro) responses were compared. Calves were immunized with KLH at either 3 weeks or up to 5 months of age and immune responses were subsequently tested. Class and subclass antibody responses were detected by ELISA, lymphocyte blastogenesis was measured using a whole blood culture technique (LTT) and skin sensitivity responses were measured as an increase in skin thickness following intradermal injection. In young calves, skin test responses were maximal at 24 h and were found to correlate with IgG1 and IgG2 responses (P less than 0.01), with IgA (P less than 0.05) but not with IgM or LTT. Histological examination of skin swellings found a sequence of cellular events, with polymorphonuclear cells dominating until 48 h after intradermal injection, when mononuclear cells became involved. However, in older calves, skin test responses correlated not only with IgG1 and IgA responses but also with lymphocyte transformation (P less than 0.05). These findings suggest that, while immune responses to KLH may be a useful indicator of immune competence in calves, interpretation should be made with caution particularly in young calves.

Animals↗

Anti-Rh(D) IgG subclasses and severity of Rh hemolytic disease of the newborn.

The influence of anti-Rh(D) IgG subclasses on the severity of hemolytic disease of the newborn was examined in 98 pregnancies. Disease was severe in 19 of 32 cases in which only IgG1 was detected, 40 of 63 cases in which IgG1 and IgG3 were found and 0 of 3 cases in which only IgG3 was detected. When both IgG1 and IgG3 anti-D were present, hemolytic disease was more severe than when IgG1 alone was detected. The earliest onset of hydrops was at 20 weeks gestation in the IgG1 + IgG3 anti-Rh group, and at 27 weeks gestation in the IgG1 group.

Erythroblastosis, Fetal↗

Erythroblastosis fetalis produced by anti-k.

We report an instance of transfusion-induced anti-k so severe that three intrauterine intravascular fetal transfusions were required. The pretransfusion circulating hemoglobin level in the fetus was 60 g/l and hematocrit was 0.19. This, to our knowledge, is the first example of the rare alloantibody, anti-k, producing erythroblastosis so severe that fetal transfusions were required in order to prevent hydrops fetalis from developing. Anti-k alloimmunization, which in a period of 20 years and 8 months occurred only once in 3,246 alloimmunized pregnancies in Manitoba, can cause severe fetal disease. The k-alloimmunized pregnant woman should be managed in the same manner as the D-, c-, or K-alloimmunized pregnant woman.

Adult↗

Failures of intravenous Rh immune globulin prophylaxis: an analysis of the reasons for such failures.

Universal administration of an ion exchange column prepared Rh immune globulin (RhIG-IV) antepartum at 28 weeks' gestation and postpartum to 9,295 Rh negative women delivering Rh positive babies has reduced the prevalence of Rh immunization from the expected 601 to 25 (a protection rate of 95.9%). Rh immunization, despite universal Rh prophylaxis, developed in 25 women; eight before antenatal prophylaxis was administered, 17 after antenatal prophylaxis was administered. Residual Rh immunization is caused by small fetal transplacental hemorrhages (TPH) (greater than or equal to 0.01 mL of fetal blood) before antenatal prophylaxis (15%) and by significant fetal TPH (greater than or equal to 0.05 mL of fetal blood) between 30 and 38 weeks' gestation (18%); TPH was too great, in some instances, for residual passive Rh antibody to give protection. Although a reduction of 62% (five of eight) of early Rh immunization and 82% (14 of 17) of later Rh immunization might be achieved by addition of 16 weeks' to 20 weeks' gestation and 34 weeks' gestation Rh prophylaxis; and a reduction of 84% overall (21 of 25) might be achieved by universal fetal TPH screening every 2 weeks from 10 weeks' gestation until delivery, with administration of RhIG when a small early fetal TPH or a significant later fetal TPH is detected, all of these programs are costly in terms of prevention of perinatal mortality and in terms of cost per quality adjusted life year gained. We believe that the costs outweigh the benefit that would be achieved. Therefore, a residual Rh immunization prevalence of 0.24% to 0.31% during or after each Rh positive pregnancy in patients at risk is to be expected despite universal 28 weeks' gestation antenatal and postnatal Rh prophylaxis.

Female↗

Fetal blood sampling in Rh hemolytic disease.

Fetal blood sampling under ultrasound guidance has added a new dimension to the management of Rh hemolytic disease. Combined with the established parameters of history, antibody measurement and amniotic fluid delta OD450 readings, direct testing of the blood of the fetus completes the picture. As well as giving information that may be applied to decisions regarding management, an opportunity is provided to observe the mechanism of anti-D IgG-induced red cell destruction in vivo.

Blood Cells↗