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Biomedical subjects

M J Stear

Publications and source records attributed to M J Stear.

At least 91 records · Page 5Linked to original sources
PubMed1989

Class I alleles of the bovine major histocompatibility system and their association with economic traits.

A total of 179 Holstein cows from the Agriculture Canada Research Branch herd at Ottawa and 271 progeny-tested Canadian Holstein bulls were typed for 37 lymphocyte antigens. Each antigen appears to be controlled by a distinct, codominant allele of the bovine lymphocyte antigen (BoLA)-A locus, which is a class I locus of the bovine major histocompatibility system. Only 10 and 16 alleles were present in Holstein cows and bulls, respectively. The association between bovine lymphocyte antigens and economically important traits was examined in gene substitution models. Separate models were used for the cow and bull data. The substitution of the W6.1 allele for the W10 allele was associated with increased protein yield in the milk in both analyses. The results were also consistent with a previous report that the presence of the W10 allele was associated with increased fat percentage compared with some, but not all, of the other alleles. However, more research is necessary to confirm these findings and to determine the biological mechanisms underlying these associations.

Age Factors↗
PubMed1989

Monoclonal antibodies to bovine major histocompatibility system antigens.

Of 89 monoclonal antibodies screened for anti-class I activity in a cytotoxic assay against bovine peripheral-blood lymphocytes, 6 reacted with all lymphocytes from all cattle tested, 72 failed to react at all and 11 reacted with polymorphic determinants. The reactivity of some of the 11 polymorphic monoclonal antibodies was dependent upon the bovine major histocompatibility system (BoLA) class I type. Eight monoclonal antibodies selected for putative anti-class II activity reacted with B-enriched lymphocytes from all cattle tested.

Animals↗
PubMed1988

Class I antigens of the bovine major histocompatibility system are weakly associated with variation in faecal worm egg counts in naturally infected cattle.

Three bulls selected for high faecal worm egg counts and three bulls selected for low faecal worm egg counts were mated to Africander-Hereford cross cows. Faecal worm egg counts were taken on four occasions from the 132 offspring. Also, each animal was typed for 32 class I antigens of the bovine major histocompatibility system (BoLA). Least squares analysis of variance showed that line, sex and some of the antigens were associated with differences in worm egg output in the faeces. After adjusting for the effects of line and sex, cattle with antigen W9 had about twice as many worm eggs in their faeces as cattle without W9; cattle with antigen CA45 had about half the concentration of faecal worm eggs as cattle without CA45. However, the antigen associations were of borderline significance at the 5% level and more work in additional populations is necessary to confirm these associations.

Animals↗
PubMed1988

BoLA antigens are associated with increased frequency of persistent lymphocytosis in bovine leukaemia virus infected cattle and with increased incidence of antibodies to bovine leukaemia virus.

The association between bovine major histocompatibility system (BoLA) type and persistent lymphocytosis in cattle with antibodies to bovine leukaemia virus was examined by comparing antigen frequencies in cattle with persistent lymphocytosis to controls matched for age, sex, breed and presence of antibodies to BLV. The cattle came from nine dairy herds in south-east Queensland, Australia; six herds were Australian Illawarra Shorthorn (AIS), two herds were Jersey and one herd was Friesian. Antigen W6 and Eu28R were more common in cattle with persistent lymphocytosis than in controls. Antigen W8 was less common in AIS cattle with persistent lymphocytosis. A study of 24 offspring from one sire, heterozygous for W10 and Eu28R, showed that offspring inheriting Eu28R from the sire were significantly more likely to have antibodies to BLV than offspring inheriting the opposing W10 haplotype.

Animals↗
PubMed1988

Breed differences in the distribution of BoLA-A locus antigens in American cattle.

A total of 627 cattle representing seven breeds from south central Nebraska, USA were tested for 37 BoLA antigens which behave as products of 37 distinct alleles of the class I BoLA-A locus. Four antigens were absent from all breeds tested. The other antigens showed marked and statistically significant differences in breed distribution. There was no evidence for blank (null) alleles. The number of alleles in each breed ranged from 10 to 20. The Hereford and Simmental populations tested were less polymorphic than the Angus, Brown Swiss, Charolais, Gelbvieh and Limousin populations.

Alleles↗
PubMed1987

Class I major histocompatibility complex antigens and C4 concentrations in sheep plasma.

Data are presented demonstrating that high concentrations of complement protein C4 in sheep plasma are associated with a particular class I OLA specificity. By way of contrast, a similar association could not be demonstrated between C3 plasma concentrations and OLA specificities. These data support the hypothesis that gene(s) determining C4 plasma concentrations are linked to the ovine MHC.

Animals↗
PubMed1987

Breed differences in the frequency of bovine lymphocyte antigens.

Lymphocytes from 1,564 cattle of 18 breeds and cross-bred groups in Australia were tested for major histocompatibility system class 1 antigens. Gene frequencies were calculated for the Angus, Belmont Red, Brahman, Hereford and Holstein-Friesian breeds. There were substantial differences among these breeds in antigen and gene frequency. There were striking differences among all 18 breeds in the presence or absence of certain antigens. Two antigens, CA13 and CA36, were strongly associated in Hereford cattle but occurred independently of each other in the other breeds.

Animals↗
PubMed1986

Antibodies to ovine lymphocytes exist in bovine alloantisera.

Forty-six percent of 149 reagents against class 1 antigens of the bovine major histocompatibility system reacted with lymphocytes from 1 or more sheep in a microlymphocytotoxicity test. The reactions fell into six groups. The majority of antisera defined an antigen present on both erythrocytes and lymphocytes. This antigen is probably the R blood group antigen and the reactions were unrelated to the presence of anticlass I activity and are probably due to the additional presence of antibodies of R specificity. The other antigens are not identical to any of the 14 red blood cell factors or seven lymphocyte antigens examined, nor did they correspond to any of the class I bovine lymphocyte antigens defined by the alloantisera.

Animals↗
PubMed1985

A comparison of bovine lymphocyte antigens.

In Canberra, 31 antigens have been described on the surface of bovine lymphocytes. Seven antigens are subgroups of other antigens. Eleven antigens are similar to the eleven antigens which have been described in Melbourne. Fourteen antigens are similar to twelve international-workshop antigens and two European-workshop antigens.

Animals↗
PubMed1984

Tick resistance and the major histocompatibility system.

199 3/4 Brahman 1/4 Shorthorn cattle, whose resistance to the cattle tick Boophilus microplus had been determined by clinical trial, were tested for 19 bovine lymphocyte antigens. Of eleven antigens detected at a frequency greater than 5%, two were found to be associated with tick resistance and a third was associated with susceptibility to ticks. However, none of these antigens accounts for more than 2.1% of the variance, indicating that these associations are not strong.

Animals↗
PubMed1984

Relationships between the bovine major histocompatibility system and commonly recognized erythrocyte and serum polymorphisms.

Linkage at a recombination frequency of 0.10 or less between the bovine major histocompatibility system and the B, C and L red blood cell groups and the albumin, haemoglobin and transferrin loci was excluded by Morton's lod score method. The white blood cell antigen CA19, which is independent of the bovine major histocompatibility system, is the J blood group.

Animals↗
PubMed1983

The antibody response to bovine lymphocyte alloantigens.

Antibodies were raised against lymphocyte cell-surface antigens by multiple immunisations with purified lymphocytes or by the exchange of skin allografts. Eighteen of 21 cattle immunised with lymphocytes raised a detectable cytotoxic antibody response. The serum antibody from 10 responders recognized only common lymphocyte antigens, those antigens which are present on all peripheral blood lymphocytes. One animal responded only to B lymphocyte antigens while 7 others responded to both classes of antigens. The amount of antibody produced varied greatly between individuals; antibody titres ranged from 1 to 1028. Antibody raised early in the response was sensitive to treatment with 2-mercaptoethanol (2-ME) suggesting that IgM was the predominant class of immunoglobulin. Subsequently antibody became resistant to this treatment suggesting the appearance of IgG. The antibody responses following the exchange of skin grafts were very similar in all 12 cattle studied. High titred antibody to common lymphocyte antigens was detected in the serum 14 days after grafting. The early antibody activity was sensitive to 2-ME treatment but became totally resistant within 14 days. Total peak antibody titres ranged from 128-2048. Antibody to B lymphocyte antigens was identified in 8 of the 12 cattle. The responses to B lymphocyte antigens were similar to those against the more widely distributed common lymphocyte antigens with respect to time of antibody appearance, time of peak titre and sensitivity to 2-ME. Peak titres ranged from 2 to 32. The change in antibody specificity with time was also studied. Sera from 11 of the 18 cattle which had responded against lymphocytes showed an increase or broadening in reaction frequency as immunisations increased, suggesting the production of antibody to secondary specificities. In the cattle which had been skin grafted, the broadest reaction patterns were seen 14 to 21 days after grafting. The broadest reaction patterns were seen when the antibody responses were at their highest titre levels and narrowed as titres decreased.

Animals↗
PubMed1983

Occurrence of cytotoxic antilymphocyte antibodies in sheep.

An earlier report that there is a high incidence (50 to 60 per cent) of cytotoxic antilymphocyte antibody in the sera of parous ewes is confirmed. This antibody is directed against paternally inherited antigens of the fetus. Antibody could be detected pre partum in four out of 34 primiparous ewes. However, there was no strong association between parity and the incidence of antibody. Antibody was also found in three out of 10 older rams which implies that pregnancy is not the only stimulus for antibody production.

Animals↗
PubMed1982

Mixed lymphocyte reactivity in cattle.

Mixed lymphocyte reactivity (MLR) in cattle was assessed by measuring the extent of cellular proliferation between allogeneic lymphocytes in an in vitro test system. To test for involvement of the bovine major histocompatibility system (BoLA) the MLR tests were done using full-sibling cattle families which had been generated through the use of embryo transfer systems. The results showed that the responses in the MLR tests were associated with the BoLA antigen sharing status between the individuals being tested. Since the tests, were done using full-sibling combinations, this result suggests genetic linkage between the MLR controlling antigens and the BoLA complex.

Animals↗
PubMed1982

Two closely linked loci and one apparently independent locus code for bovine lymphocyte antigens.

Twenty different antigens have been detected on bovine lymphocytes. Family studies suggested that 19 of the antigens were under the control of two closely-linked loci. The remaining antigen was apparently coded for by an independent locus. The distribution of the antigens in the population also suggested that three loci control the expression of lymphocyte antigens. A co-capping study on two antigens which were inherited together on one haplotype showed that these antigens were expressed on different molecules on the lymphocyte membrane, providing further evidence for the existence of two linked loci.

Animals↗
PubMed1982

A method for freezing sheep lymphocytes prior to cytotoxicity testing.

The two stage freezing technique was adapted for use with sheep lymphocytes. Parameters investigated were lymphocyte concentration, composition of thawing medium and DMSO concentration. The main difference between this and earlier published techniques is the use of a high DMSO concentration (17%). The technique adopted was both simple and reliable. It consistently gave lymphocyte viabilities of 95% or more in thawed cell suspensions. The procedure is apparently without effect on lymphocyte antigen expression and thus appears very suitable for use in microlymphocytotoxicity tests.

Animals↗