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Biomedical subjects

W I Morrison

Publications and source records attributed to W I Morrison.

At least 55 records · Page 3Linked to original sources
PubMed1994

Immunity to a parasite that transforms T lymphocytes.

The past year has seen the first direct evidence that parasite-specific CD8+ T cells can protect cattle against patent infection with Theileria parva. These studies were based on the adoptive transfer between monozygous twins of lymphocytes responding to a challenge with the parasite. Immunization trials are also continuing with a candidate neutralizing vaccine based on the dominant antigen of the T. parva sporozoite surface. This progress has considerably enhanced the prospects for an improved vaccine against the parasite.

Animals↗
PubMed1994

Identification of three distinct allelic forms of bovine CD4.

The CD4-specific monoclonal antibody (mAb) CC26, when tested on a total of 143 cattle, failed to react with T cells from 16% of animals and gave reduced intensity staining in a further 35% of animals. The results of family studies with groups of half- and full-siblings indicated that CC26 recognizes an allele of CD4 which is co-dominantly expressed in heterozygous animals. This was confirmed by sequential immunoprecipitation and by selecting transfectants expressing the CC26+ and CC26- allelic forms of CD4 following transfection of genomic DNA from a heterozygous animal. Biochemical studies also revealed an allelic difference in the relative molecular weight (M(r)) of the CD4 molecule, one allele giving 49,000/52,000 MW bands and the other 52,000/57,000 MW bands in sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Treatment of CD4+ cell lines with tunicamycin resulted in the appearance of a 47,000 MW band for both allelic forms indicating that the difference in M(r) is due to glycosylation. All of the CC26+ alleles examined were of the low molecular weight form (M(r)low) whereas both M(r)low and M(r)high alleles were represented in CC26- animals. Thus, on the basis of M(r) and reactivity with mAb CC26, three allelic forms of bovine CD4 can be identified, namely CC26+ M(r)low, CC26- M(r)low and CC26- M(r)high; it is proposed that these alleles are designated CD4.1, CD4.2 and CD4.3, respectively. The allelic difference detected by CC26 was present in both Bos taurus and B. indicus cattle indicating that it had arisen prior to divergence of these subspecies. The M(r)high allele (CD4.3) was detected only in B. indicus animals.

Alleles↗
PubMed1993

The growth of cell culture-attenuated rinderpest virus in bovine lymphoblasts with B cell, CD4+ and CD8+ alpha/beta T cell and gamma/delta T cell phenotypes.

Cloned bovine lymphoblastoid cell lines, transformed by the protozoan parasite Theileria parva were infected with cell culture-attenuated rinderpest virus vaccine. The virus grew readily in lymphoid B cells, CD4+ and CD8+ alpha/beta T cells and gamma/delta T cells producing new infectivity, viral antigens, c.p.e. and total cell death. There did not appear to be a predilection for any particular phenotype of lymphoblast. The results imply that if the vaccine causes immunosuppression, it could do so through a variety of mechanisms.

Animals↗
PubMed1992

Molecular characterization of the WC1 antigen expressed specifically on bovine CD4-CD8- gamma delta T lymphocytes.

Although gamma delta T lymphocytes were identified several years ago, the functional importance of these cells remains to be established. gamma delta T cells of ruminants are unique in two respects. First, they are present at much higher levels compared to man and rodents. Second, ruminant CD4-CD8- gamma delta T cells uniquely express a 220 kD surface Ag recognized by a panel of mAb, recently clustered as WC1. WC1 has been most extensively studied in sheep with the use of the mAb T19. Here, we report on the isolation of a full length cDNA clone, encoding the WC1 Ag, from a COS cell cDNA expression library prepared from a bovine gamma delta T cell line. The protein encoded by the pWC1 cDNA clone was reactive with the bovine mAb CC15 and IL.A29, and with T19. The cDNA clone consisted of 4475 bp and contained a single long open reading frame of 1436 amino acids. The pWC1 cDNA clone encoded a type 1 integral membrane protein with an extracellular domain consisting of 11 scavenger receptor cysteine-rich-repeats with homology to CD5 and CD6. Southern blotting suggested that the bovine genome contained multiple sequences highly related to the isolated WC1 cDNA. Furthermore, WC1-like sequences were present in the genomes of all mammals tested including mouse and man. The molecular characterization of the WC1 Ag as reported here provides a starting point for the definition of its role in gamma delta T cell biology.

Amino Acid Sequence↗
PubMed1992

Afferent lymph veiled cells prime CD4+ T cell responses in vivo.

The interdigitating cell (IDC) population of the lymph node paracortex is believed to be responsible for the induction of CD4+ T cell responses to soluble antigens. We have examined the role of afferent lymph veiled cells (ALVC), the putative precursors of IDC, in the induction of primary bovine CD4+ T cell responses in vivo. ALVC prepared from lymph draining an antigen inoculation site stimulated maximal responses in antigen-specific T cell clones as soon as 30 min after inoculation. In addition, antigen-pulsed ALVC were shown to induce primary antigen-specific T cell responses when administered in vivo. Observed influences of fixation and the addition of chloroquine or class II major histocompatibility complex-specific monoclonal antibodies on presenting function confirmed that ALVC process and present antigens using the endosomal pathway. We conclude that ALVC rapidly internalize antigens deposited in the periphery, and process them for presentation to naive T cells in the draining lymph node. Their function is, therefore, likely to be an important factor in the induction of primary T cell responses to soluble antigens in vivo.

Animals↗
PubMed1992

Transmembrane and cytoplasmic domain sequences demonstrate at least two expressed bovine MHC class I loci.

We have used the polymerase chain reaction to amplify cDNA from expressed bovine major histocompatibility complex class I genes. Sequences obtained from transmembrane and cytoplasmic domains were used to identify the number of expressed alleles. Data from three animals suggest that there are four major expressed alleles, representing the products of two (or more) loci. We have also demonstrated the presence of an alternatively spliced mRNA, which has been observed in five animals. The alternative splicing removes exon 7 (the major site of class I phosphorylation), which predicts a truncated molecule with a cytoplasmic portion 16 amino acids shorter than usual. This phenomenon was detected for only a single class I allele within each individual.

Alternative Splicing↗
PubMed1992

Standardization of a technique for analysing the frequency of parasite-specific cytotoxic T lymphocyte precursors in cattle immunized with Theileria parva.

A limiting dilution microculture system was optimized to quantify the frequency of Theileria parva-specific cytotoxic T lymphocyte precursors (CTLp) in peripheral blood mononuclear cells (PBMC) from immune cattle. Optimal results were obtained with responder cell input levels ranging from 2 x 10(4)/well to 6.25 x 10(2)/well, along with 1-5 x 10(3)/well stimulator cells in standard supplemented RPMI 1640 medium containing 2.5-5% T cell growth factors. Thirty-six microtitre wells were established at each responder input level. Cultures were incubated for 7 days at 38 degrees C, at the end of which time individual wells were screened for cytotoxic activity in a 4-h 111indium oxine-release assay. Analysis of the cytotoxicity data, by a computer-programmed maximum likelihood estimation method indicated that they conformed to the Poisson model of single-hit kinetics. Estimates of frequencies ranged from 1:3600 to 1:5275 CTLp in PBMC of eight cattle between 1 and 24 months after immunization with T. parva. By contrast, no CTLp were detected in six naïve animals analysed to a responder cell input of 10(5)/well. Split-well analysis of individual microwells showed that the CTL clones generated under limiting dilution conditions displayed exquisite specificity for parasitized cells, were genetically restricted and in some animals were parasite strain-specific.

Animals↗
PubMed1991

Bovine afferent lymph veiled cells differ from blood monocytes in phenotype and accessory function.

Veiled cells have been prepared from bovine afferent lymph and their surface phenotype has been compared with that of blood monocytes using a panel of mAb that define bovine leukocyte Ag. It has been observed that the expression of CD1c and a putative bovine CD45R Ag is restricted within these populations to afferent lymph veiled cells (ALVC), whereas CD11b is expressed only on monocytes. The CD11a and CD11c specificities and an additional Ag defined by mAb 1LA24 (p110/75) are expressed by both cell types, although CD11a and p110/75 are found only on subpopulations of ALVC. In a comparison of accessory function, we have found that ALVC are considerably superior to blood monocytes both as stimulators in mixed leukocyte cultures and as presenters of soluble Ag to primed T cells. This superiority appears to be associated with an increased capacity to form clusters with responding lymphocytes. In addition, we have established that the capacity of ALVC to present soluble Ag to Ag-specific T cell clones resides almost exclusively in a subpopulation defined by the phenotype p110/75+ CD11a-.

Animals↗
PubMed1991

Distinction of naive and memory BoCD4 lymphocytes in calves with a monoclonal antibody, CC76, to a restricted determinant of the bovine leukocyte-common antigen, CD45.

A murine IgG1 monoclonal antibody (mAb), CC76, has been produced that, based on findings of the relative molecular mass of polypeptides that it recognized, staining of leukocytes in blood and tissues, and the biological properties of the T lymphocyte subpopulations with which it reacts, is considered to identify an isoform of the leukocyte common antigen (LCA) family of molecules in cattle. The mAb is more similar to human CD45R which detect products requiring the presence of the B exon within the LCA gene and to the anti-rat mAb MRC-OX22, than to CD45RA or CD45R0. mAb CC76 reacts with an antigen expressed by subpopulations of cells in bovine blood that express BoCD2 and either the BoCD4 or BoCD8 antigens. T cells that express the gamma/delta T cell receptor identified with mAb to BoWC1 antigen did not react with CC76. The molecule detected is expressed on B cells but not on monocytes or granulocytes. Only 2% of cells in thymic suspensions stained with mAb CC76. Immature cortical thymocytes that were BoCD1+ did not react with CC76 and 90% of the cells in thymic suspensions that were CC76+ had the phenotype of mature thymocytes. These cells were primarily in the medulla. The LCA isoform detected thus appears to be acquired by mature cells shortly before emigration from the thymic medulla into the periphery. Expression of the molecule detected by mAb CC76 on cells from lymph nodes was similar to that in blood, but expression on cells from the gut mucosa was quite different. Almost all, 95% and 93% respectively, of the BoCD4+ cells in the gut mucosa or discrete Peyer's patches were CC76-. A greater proportion of BoCD8+ cells from these sites, 35% and 26%, expressed the antigen. Lymphocytes from animals that had been immunized with Trypanosoma brucei were sorted into BoCD4+, CC76+ and BoCD4+, CC76- populations and cultured in vitro with the variable surface glycoprotein antigen from the parasite. Lymphocyte transformation responses were entirely within the CC76- population indicating that the mAb distinguished naive from memory BoCD4+ T cells in cattle. Major histocompatibility complex (MHC) class I-restricted cytotoxic precursor cells that expressed the BoCD8 antigen sorted from cattle that were immune to Theileria parva were both CC76+ and CC76- indicating that different isoforms of the LCA may be expressed on MHC class I- and class II-restricted memory cells and that BoCD8 memory cells are heterogeneous with respect to the LCA isoform that they express.

Animals↗
PubMed1991

Individual antigens of cattle. Differentiation antigens expressed predominantly on CD4- CD8- T lymphocytes (WC1, WC2).

The 14 mAbs representing workshop cluster 1 recognise a 215/300 kDa antigen expressed on a subpopulation of lymphocytes which express low levels of CD5 but are negative for other B and T cell markers defined by workshop antibodies. Separate studies with cDNA probes for bovine CD3 and T cell receptor indicate that these lymphocytes are gamma/delta T cells. It is of note that the different mAbs react with varying proportions of this cell population, suggesting that the antigen undergoes considerable post-translational modification. A further two mAbs, designated workshop cluster 2, react with a 37/47 kDa heterodimeric molecule expressed in a subpopulation of the WC1+ cells and on an additional small population of T lymphocytes. The cell populations recognised by the two mAbs are different although they overlap in some animals. It is suggested that these mAbs may be specific for T cell receptor molecules.

Animals↗
PubMed1991

Analysis of the reactivity of anti-bovine CD8 monoclonal antibodies with cloned T cell lines and mouse L-cells transfected with bovine CD8.

Mouse L-cells transfected with bovine CD8 and two Theileria parva-infected cloned T cell lines expressing bovine CD8 were used to screen the panel of ten monoclonal antibodies (mAbs) submitted to the workshop. Eight of the ten mAbs reacted with the transfectant and both the cloned T cell lines. However, two mAbs CC58 and BAT82A did not recognise the transfectant and only reacted with one of the T cell lines. Further biochemical studies indicated that the eight mAbs react with both homo- and heterodimeric forms of bovine CD8 whilst the two mAbs CC58 and BAT82A react with only heterodimeric forms. These data suggest that bovine DC8 is encoded by two genes as is the case in mouse and man.

Animals↗
PubMed1991

Cell surface phenotype of two cloned populations of bovine lymphocytes displaying non-specific cytotoxic activity.

Monoclonal antibodies specific for T cell differentiation antigens were tested on four cloned populations of lymphocytes derived from the peripheral blood mononuclear cells of an animal immunised with Theileria parva. The clones were defined functionally in terms of cytotoxic activity, MHC restriction and expression of messenger RNA for CD3 and T cell receptor (TCR). Two clones contained RNA transcripts for CD3, TCR-alpha and beta and were positive for CD2, CD5 and CD6; one of these was a typical CD4+ class II MHC-restricted non-cytotoxic clone while the other was a CD8+ class I MHC-restricted cytotoxic clone. By contrast, the remaining two clones had the characteristics of non-specific killer cells in that they exhibited moderate levels of non-MHC-restricted killing; they contained TCR-delta mRNA and a 1.2 kb truncated form of TCR-beta message, but they did not contain CD3 or TCR-alpha mRNA. One of these non-specific killer clones only expressed CD2 whereas the other clone only expressed CD8, but without the CD8 determinant recognised by monoclonal antibodies CC58 and BAT52. All four clones were negative for the WC1 antigen which is expressed on gamma/delta T lymphocytes.

Animals↗
PubMed1991

Polymorphism of the CD4 and CD5 differentiation antigens in cattle.

Monoclonal antibodies (mAbs) specific for bovine CD4 and CD5 antigens have been found to identify polymorphic determinants on these molecules. In the case of CD5, mAb IL-A67 recognises one allotypic form of the antigen while four other CD5-specific mAbs in the workshop (CC17, CC29, BLT-1 and 8C11) recognise a second allotype. The CD4-specific mAbs submitted to the workshop reacted with the cells of all animals tested. However, a further two mAbs (CC26 and IL-A18) specific for CD4 were found to react with cells only from about 85% of animals tested. Sequential immuno-precipitation experiments together with family studies showed that the allotypes of CD4 and CD5 are both inherited in a simple Mendelian manner and are co-dominantly expressed. One of the CD5 allotypes was not detected in Bos taurus animals while the gene frequency of the second allotype was only about 10% in the B. indicus animals tested. The gene frequency of the CD4 allotype detected by CC26 and IL-A18 was similar in the two sub-species.

Animals↗
PubMed1991

Characterization of a polymorphic immunodominant molecule in sporozoites and schizonts of Theileria parva.

This study examines several aspects of a polymorphic, immunodominant molecule (PIM) found in the protozoan parasite, Theileria parva. The antigen is present in all T.p. parva stocks examined, and in the related subspecies, T.p.bovis and T.p.lawrencei. It is the predominant antigen recognized by antisera from immune cattle on Western blot analysis of schizont-infected lymphocytes, and is the only antigen which has been shown to react with anti-schizont monoclonal antibodies (MoAbs) on Western blots or in immunoprecipitations. The antigen shows polymorphism in both size and expression of antibody epitopes among the different stocks of T. parva. The antigen is present in sporozoites as well as schizonts.

Animals↗