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C R Mackay

Publications and source records attributed to C R Mackay.

At least 91 records · Page 5Linked to original sources
PubMed1991

Prominence of gamma delta T cells in the ruminant immune system.

The lymphoid systems of sheep and cattle contain a large number of gamma delta T cells, in striking contrast to the lymphoid systems of humans and mice. In neonatal animals particularly, these cells comprise the predominant fraction of T cells in the blood. Here Wayne Hein and Charles Mackay discuss what is currently known about the ontogeny, phenotype, tissue distribution and function of gamma delta T cells in ruminants. There are a number of interesting molecular features that characterize ruminant gamma delta T cells, but these do not entirely explain the high frequency of use of the gamma delta T-cell receptor in these animals. Studies on sheep, cattle or other animals that preferentially use gamma delta T cells should provide insights into the biological significance of the existence of two distinct forms of the T-cell receptor.

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PubMed1990

Naive and memory T cells show distinct pathways of lymphocyte recirculation.

In this report, we have addressed two questions concerning immunological memory: the way in which naive and memory T cells recirculate through the body, and the intrinsic rate of division within the naive and memory populations. We identified naive and memory T cells in sheep by their cell surface phenotype and their ability to respond to recall antigen. Memory T cells were CD2hi, CD58hi, CD44hi, CD11ahi, and CD45R-, as pertains in man. T cells that crossed from blood to the tissues of the hind leg and accumulated in the popliteal afferent lymph were all of memory phenotype. Conversely, T cells in efferent lymph, 90% of which entered the lymph node (LN) via high endothelial venules (HEV), were mostly of the naive phenotype (CD2lo, CD58lo, CD44lo, CD11alo, and CD45R+). The marked enrichment of these two phenotypes in different recirculatory compartments indicated that memory T cells selectively traffic from blood to peripheral tissues to LN (via afferent lymph), whereas naive T cells selectively traffic from blood to LN (via HEV). We argue that the differential use of these two recirculation pathways probably optimizes lymphocyte interactions with antigen. The nonrandom distribution of T cell subsets in various recirculatory compartments may be related to the relative proportion of memory cells in each subset. In particular, gamma/delta T cells in blood were almost exclusively of memory phenotype, and accumulated preferentially in afferent, but not in efferent, lymph. Finally, using the bromo-deoxyuridine labeling technique, we found that at least a sizeable proportion of memory T cells, whether in blood or afferent lymph, were a dividing population of cells, whereas naive T cells were a nondividing population. This result supports an alternative model of lymphocyte memory that assumes that maintenance of memory requires persistent antigenic stimulation.

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PubMed1989

Gamma/delta T cells express a unique surface molecule appearing late during thymic development.

The vast majority of T cells in man and mouse use the alpha/beta form of T cell receptor (TcR), and express either CD4 or CD8, whereas the small subset of gamma/delta T cells are usually CD4-CD8-. In contrast to man and mouse, the gamma/delta subset in sheep, defined here using an anti-gamma/delta monoclonal antibody (mAb), comprises 30%-60% of T cells. We show that gamma/delta T cells in sheep express a unique surface molecule termed T19 which is 215 kDa in size and unrelated to either CD45 or the TcR. The T19 molecule was expressed at a distinct stage during gamma/delta T cell ontogeny within the thymus, since gamma/delta thymocytes which appeared early in fetal ontogeny were T19- and also major histocompatibility complex (MHC) class I- and localized almost exclusively to the outer cortex and cortex of the thymus. "Mature-type" gamma/delta thymocytes which emerged late in thymic development were T19+ and MHC class I+ and localized predominantly to the thymic medulla. The sequence of events indicated that these cells were most likely derived from the early gamma/delta thymocytes. These medullary gamma/delta thymocytes showed a very distinctive association with Hassall's corpuscles, suggesting a role for these structures in gamma/delta thymocyte maturation. In the periphery, T19 was expressed exclusively within the gamma/delta T cell subset, however some gamma/delta T cells were T19-. In particular, a large proportion of gamma/delta T cells within intestinal epithelium lacked T19, indicating a correlation between T19 expression and either function or homing patterns of gamma/delta T cells. Both T19+ and T19- gamma/delta T cells were CD2-, and expressed low levels of LFA-1 and CD5. In addition, gamma/delta T cells recirculated differently from other T cells, and appeared not to enter mesenteric lymph nodes at all from the blood. We propose that T19 is a maturation marker for gamma/delta T cells. In addition, the exclusive expression of T19 by gamma/delta T cells indicates that this molecule most likely serves a fundamental role in the interactions and function of gamma/delta T cells.

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PubMed1989

A large proportion of bovine T cells express the gamma delta T cell receptor and show a distinct tissue distribution and surface phenotype.

The numbers, phenotype, and tissue distribution of gamma delta T cells in cattle were studied using two monoclonal antibodies (mAbs) which react with the bovine gamma delta T cell receptor (TCR). Both mAbs stained 20-40% of T cells in peripheral blood, and immunoprecipitated molecules of 44 and 36 kd (reduced) and 70-80 kd (non-reduced). In cattle the majority of circulating gamma delta T cells showed a distinct surface phenotype; they expressed T19, a 215 kd molecule described in sheep and cattle which marks only gamma delta T cells. Bovine gamma delta T cells were also CD2-, CD4-, and mostly CD8-, and failed to express CD6, a molecule possibly involved in T cell activation. The distribution of gamma delta T cells in cattle lymphoid tissues differed markedly from that in humans, in that bovine gamma delta T cells were concentrated around lymph node trabeculae and were usually sparse or absent from the B cell and T cell domains of lymph nodes. Like most other species studied, gamma delta T cells in cattle were localized to epithelial surfaces, particularly within the skin and intestine, indicating that it was at these sites where gamma delta T cells functioned. Our results provide further evidence for the unusual localization, recirculation pattern, and phenotype of gamma delta T cells, and also show that some features of gamma delta T cells can differ quite markedly from species to species.

Animals↗
PubMed1989

Surface expression of differentiation antigens on lymphocytes in the ileal and jejunal Peyer's patches of lambs.

The surface phenotype of lymphocytes in the ileal (IPP) and jejunal (JPP) Peyer's patches (PP) of lambs was compared using flow cytometry and immunohistology with a panel of monoclonal antibodies (mAb). The B-cell markers p220, BAS9A and surface Ig molecules were detected on 70-95% of cells from the IPP. T-cell markers were detected on less than 1% of IPP lymphocytes, confirming that the IPP in lambs contains virtually only B lymphocytes. The JPP contained a lower proportion of B cells and 16% T cells, nearly all of which expressed the CD4 molecule. Interestingly, the reactivity of a fourth B-cell markers, BAQ44a, differed from this pattern; only 12% of IPP lymphocytes were positive whereas 70% of JPP lymphocytes expressed this marker. A majority of both IPP and JPP lymphocytes (80-95%) expressed the cell adhesion molecules CD11a (LFA-1) and LFA-3. Other adhesion molecules, such as CD2 and CD44, were expressed by fewer cells from the IPP than from the JPP. MHC class I antigens were detected on more than 95% of lymphocytes from both the IPP and JPP. In the case of MHC class II antigens, more positive cells occurred in the IPP (greater than 95%) than in the JPP (80%). The in situ localization of cell-surface antigens was assessed by immunohistology. CD4+ T cells occurred in the interfollicular T-cell regions and in JPP follicles, whereas CD8+ T cells localized only in the interfollicular regions and were absent from follicles. The pattern of expression of B-cell markers, adhesion molecules and MHC antigens indicated that a gradient of increasing maturity of B cells existed within follicles from the base towards the dome region. The data presented here lend support to the notion that the IPP in lambs represents a novel B-cell lymphoid tissue with a function different from that of the conventional Peyer's patches found in the jejunum.

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PubMed1988

Lymphocyte subsets show marked differences in their distribution between blood and the afferent and efferent lymph of peripheral lymph nodes.

The surface phenotypes (CD1, CD4, CD5, CD8, SBU-T19, MHC class I, MHC class II, and sIg) of cells in blood, lymph nodes, and lymph were determined to examine simultaneously the distribution of lymphocyte subsets circulating in blood, afferent lymph, and efferent lymph of a peripheral lymph node. Marked differences in the percentage of certain lymphocyte subsets were apparent within the compartments examined, suggesting that lymphocyte subsets leave the blood with differing efficiencies. Lymphocyte subsets also appeared to be extracted from the blood at different rates by lymph node as opposed to subcutaneous vascular endothelium. Endothelial cells in different vascular beds may express different numbers of molecules complementary to a set of migration-related cell surface molecules specific for each lymphocyte subset. Accordingly, the vascular endothelium would be the key factor in regulating nonrandom cell migration.

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PubMed1988

Unusual expression of CD2 in sheep: implications for T cell interactions.

The CD2 adhesion/activation molecule on the surface of mammalian T lymphocytes binds to a ubiquitous receptor, LFA-3. We show that CD2 in sheep differs significantly in its expression from CD2 in humans, and this most likely relates to the high level of expression of the sheep LFA-3 molecule. In sheep, in contrast to man, CD2 was weakly expressed on peripheral T cells and thymocytes. Moreover, a large subset of T cells identified by the monoclonal antibody T19 and considered to be gamma/delta receptor-bearing T cells completely lacked the CD2 molecule. T19+ cells constituted up to 50% of peripheral blood T cells in lambs, and 20-30% of T cells in older sheep, whereas the CD4+ and CD8+ subsets, which are both CD2+, constituted relatively small subsets in peripheral blood. Only those T cells which did express CD2 adhered as "rosettes" to dendritic cells, and the localization of CD2 to the membrane junction indicated that CD2 was critical for this adhesion. However, CD2 adhesion was not necessary for CTL-mediated killing of allogeneic target cells, since T19+ cells generated in bulk mixed lymphocyte culture were extremely efficient at killing appropriate target cells. Some of the behavioral differences between T19+ and CD4+/CD8+ subsets might be explained by the presence or absence of CD2. The results also indicate that the expression of CD2 (and LFA-3) may differ markedly between species.

Animals↗
PubMed1988

Characterization of a 95,000 molecule on sheep leucocytes homologous to murine Pgp-1 and human CD44.

The phagocyte glycoprotein-1 (Pgp-1) antigen of mice is a 94,000 MW molecule with a wide tissue distribution, but no attributed function. We produced a monoclonal antibody (mAb) termed 25-32 which recognizes the Pgp-1 molecule of numerous mammalian species, including humans and sheep. Preclearing experiments with I42/5, a rat anti-mouse Pgp-1 mAb that cross-reacts with human Pgp-1, established the specificity of 25-32 for human and sheep Pgp-1. Moreover, an antibody recognizing human CD44, termed F10-44-2, also reacted with the same molecule as that recognized by 25-32 and I42/5, so establishing the co-identity of CD44 and Pgp-1. Within the sheep thymus, Pgp-1 was expressed most strongly by medullary thymocytes and stromal cells, and by small numbers of cells at the subcapsular cortex. Pgp-1 was expressed early in thymic ontogeny; all 35-40-day gestation fetal sheep thymocytes were intensely Pgp-1+, but by 80 days the number of reactive thymocytes had decreased to adult levels. The expression of Pgp-1 on lymphocytes was markedly increased after stimulation with mitogens, or with phorbol esters and ionomycin. The highly conserved nature of Pgp-1 through evolution, its expression on virtually all cell types within the body, and its increased expression on rapidly dividing cells indicate that this molecule mediates an important function, possibly serving as a hormone or metabolite receptor.

Animals↗
PubMed1987

A monoclonal antibody to the p220 component of sheep LCA identifies B cells and a unique lymphocyte subset.

The leukocyte common antigen (LCA, CD45) of humans and rodents is expressed exclusively by leukocytes, and has been implicated in a number of immune functions (1-4), although its precise function is still unknown. Three monoclonal antibodies (mAbs) were produced which identified different epitopes on the LCA of sheep. mAbs 1-11-32 and 38-42 reacted with determinants of LCA expressed on all leukocytes, but showed differential reactivity with thymocytes. Another antibody, 20-96, identified an epitope of LCA expressed mainly on B cells, but also on a unique lymphocyte subset contained mostly in peripheral blood, which was 20-96high, sIg-, CD4-, CD8-, SBU-T19-, but CD5+. These cells constituted only 5-6% of PBL. The cellular lineage of this latter subset is uncertain since these cells appeared to be unrelated to B cells, and were absent from the thymus. Unlike the other two mAbs to LCA, 20-96 was not reactive with macrophages and granulocytes. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of material immunoprecipitated by the "pan" LCA-specific mAbs revealed lymphocyte forms with molecular weights (MW) of 220, 210, and 190K, whereas 20-96 immunoprecipitated only a 220K MW form. The expression and MW of LCA on thymocytes or ileal Peyer's patch (IPP) cells differed from those on peripheral lymphocytes. B cells in IPP, which constitute 98% of cells, expressed the 20-96 determinant at low density, in contrast to its high expression on peripheral B cells. LCA from IPP existed in two forms of 220 and 190K MW, whereas LCA from peripheral B cells was entirely 220K MW, and thymus 210 and 190K MW.

Animals↗
PubMed1987

Lymphocyte antigens of sheep: identification and characterization using a panel of monoclonal antibodies.

A panel of monoclonal antibodies has been developed and used to identify and characterize the lymphocyte antigens of sheep. These studies have shown that sheep lymphocyte antigens display similar, if not identical, tissue distributions to their analogues in other species. Some of the major sheep antigens, including CD5, CD4, CD8, SBU-T19, Pgp-1, LCA and the MHC antigens, are described in detail.

Animals↗
PubMed1987

Ontogeny of ovine lymphocytes. II. An immunohistological study on the development of T lymphocytes in the sheep fetal spleen.

The development of T and B lymphocytes in the ovine fetal spleen was studied immunohistologically using a panel of monoclonal antibodies. A specific sequence of appearance of lymphocyte markers on cells was observed. At 43-44 days of gestation, SBU-T1- and SBU-T8-positive lymphocytes were present in low numbers. However, no SBU-T4, 20.96-, 25.69-, 38.38-, or 46.66-positive lymphocytes were seen until 50-55 days of gestation. Surface immunoglobulin (sIg) was first detected on fetal spleen cells at 45-50 days of gestation. SBU-T19 lymphocytes appeared later in gestation, being observed in fetal spleens at 57 days gestational age (g.a.). The distribution of T cells, B cells and MHC antigens in the developing spleen of the ovine fetus is described.

Animals↗
PubMed1987

Ontogeny of ovine lymphocytes. III. An immunohistological study on the development of T lymphocytes in sheep fetal lymph nodes.

The development of T lymphocytes in ovine fetal lymph nodes was studied immunohistologically using a panel of monoclonal antibodies. T lymphocyte subsets appeared within the ovine fetal lymph node in a specific sequence. SBU-T1- and SBU-T8-positive lymphocytes were seen at Day 47 of gestation. LCA, sIg, MHC I, MHC II, SBU-T6 and 46.66 antigens were also seen within the lymph node at this time. The first SBU-T4-positive cells were seen within the fetal lymph node at Day 50 of gestation, along with the first 20.96-, 25.69- and 38.38-positive cells. SBU-T19 lymphocytes appeared later in gestation, being present in fetal lymph nodes from Day 69 of gestation. The appearance and distribution of T and B cells in the developing lymph nodes of the ovine fetus is described and compared with the ontogeny of lymphocytes in the fetal thymus and spleen.

Animals↗
PubMed1987

Ontogeny of ovine lymphocytes. I. An immunohistological study on the development of T lymphocytes in the sheep embryo and fetal thymus.

The time of appearance of lymphocytes expressing T-cell markers and the subsequent development of the fetal thymus were studied in ovine embryos using a panel of monoclonal antibodies. Leucocyte common antigen (LCA) and major histocompatibility complex class I (MHCI) antigens were seen on a small number of cells within the ovine embryo at Day 19 of gestation. SBU-T6 (CD1)-positive cells were found at Day 22 of gestation, while major histocompatibility complex class II (MHC II) antigens were first observed at Day 25 of gestation. Large basophilic cells, weakly staining for SBU-T1 (CD5), were present in the mesenchyme of the neck and in the dorsal mediastinum and mesentery of embryonic sheep of 33 days gestational age (g.a.); however, no SBU-T1-positive cells were detected in the thymus at this time. No SBU-T4 (CD4)- or SBU-T8 (CD8)-positive cells were detected in any organs of embryos of this age. SBU-T4- and SBU-T8-positive cells were first seen in fetal thymi, and elsewhere within the fetus, at 35-38 days g.a. SBU-T19-positive cells were first seen within the fetal thymus at 50-58 days g.a.

Animals↗
PubMed1986

Thymocyte subpopulations during early fetal development in sheep.

Phenotypic analysis of thymocytes during fetal development may identify subpopulations which are either absent or difficult to detect in postnatal thymus. A panel of monoclonal antibodies specific for sheep lymphocyte antigens (SBU-T1, -T4, -T8, -T6) was used to identify thymocyte subpopulations in postnatal and fetal sheep. Thymuses were analyzed by two-color immunofluorescence and flow cytometry or by immunohistology. Two-color immunofluorescent staining of postnatal sheep thymus with anti-SBU-T4 and anti-SBU-T8 revealed four relatively distinct subpopulations with particular localizations: a) SBU-T4-T8-, predominantly outer cortex (12%); b) SBU-T4+T8+, inner cortex (74%); c) SBU-T4+T8-, medulla (10%), and d) SBU-T4-T8+, medulla (4%). One- and two-color immunofluorescent analysis of cells from early fetal thymuses demonstrated the appearance of SBU-T8+ cells well before SBU-T4+ cells. Immunohistologic staining of fetal sheep thymus at various stages of gestation (term = 150 days) revealed that lymphoid cells and MHC class II-positive dendritic cells first appeared at 35 days, at which stage the thymic epithelium was weakly positive for class I MHC antigens but negative for class II MHC antigens. The earliest lymphocyte antigens detectable on fetal sheep thymocytes were SBU-LCA and SBU-T1. By 40 days, the antigens SBU-T6, SBU-T4, and SBU-T8 were detectable on a small number of thymocytes; SBU-T8 preceded SBU-T4, and the number of SBU-T8+ thymocytes always exceeded the number of SBU-T4+ thymocytes throughout early gestation. At 50 days, a thymic medulla appeared and thereafter grew rapidly in size. Immunoperoxidase staining of serial sections of the fetal neck revealed cortical-type thymocytes outside the thymus from 40 days onward, before the appearance of a thymic medulla. However, by 60 days, only medullary-type thymocytes were observed either extrathymically or within the interlobular septa of the thymus, indicating that only thymocytes with a medullary phenotype leave the thymus from this stage of gestation.

Animals↗
PubMed1986

Three distinct subpopulations of sheep T lymphocytes.

Monoclonal antibodies reactive with distinct T lymphocyte subpopulations have been described in man, mouse and rat and structural analyses of these antigens have demonstrated a high degree of evolutionary conservation. This report describes the reactivity of three monoclonal antibodies (mAb), 19-19, alpha SBU-T4 and alpha SBU-T8, which define T cell subpopulations in the sheep. The mAb alpha SBU-T4 and alpha SBU-T8 define the sheep CD4 and CD8 molecules, respectively. These two antigens show similar tissue distributions, molecular weights and fluorescence-activated cell sorter profiles to human, mouse and rat CD4 and CD8 molecules. The mAb 19-19 is reactive with a subpopulation of T lymphocytes which displays a tissue distribution unlike that reported for a T cell subset in any other species. 19-19 stains 7% of efferent lymph lymphocytes, 15% of peripheral blood lymphocytes but only 1-3% of lymph node lymphocytes. Two-color immunofluorescence demonstrates that the 19-19+ T cell subset is SBU-T4- and SBU-T8-, and thus defines a third T cell subpopulation in sheep. Immunohistology on frozen lymph node tissue sections localizes 19-19 mAb-reactive cells to the subcapsular region of the lymph node and lymph node trabeculae. Only 1% of thymocytes are 19-19+ and these cells are located mainly in the medulla and often arranged as foci around blood vessels. The 19-19 mAb immunoprecipitates from sheep lymphocytes an antigen with an apparent molecular mass of 215 kDa under both reducing and nonreducing conditions. It is concluded that alpha SBU-T4 and alpha SBU-T8 recognize the sheep homologues of the human T4 and T8 antigens, respectively, whereas 19-19 recognizes an antigen (termed SBU-T19) which has not been reported in any other species.

Animals↗
PubMed1986

Four antigens expressed on most ovine cell types.

Monoclonal antibodies have been produced that bind to four different antigens expressed on the surface of ovine lymphocytes as well as to a variety of other ovine cell types. These antigens have been characterized with respect to their tissue distribution and immunochemistry. The timing of appearance of these antigens within the ovine embryo is reported.

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