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Biomedical subjects

M R Brandon

Publications and source records attributed to M R Brandon.

At least 127 records · Page 7Linked to original sources
PubMed1985

Sheep lymphocyte antigens (OLA). II. Major histocompatibility complex class II molecules.

A panel of monoclonal antibodies have been produced which recognize monomorphic determinants of sheep MHC Class II antigens, including an allogenically derived murine monoclonal antibody specific for the I-E gene product. Immunoprecipitation and SDS-PAGE analyses indicates that these monoclonal antibodies recognize a non-covalently associated glycoprotein complex of molecular weight 30-32 kDa (alpha chain) and 24-26 kDa (beta chain). One and two colour immunofluorescence was used to measure the distribution of these 'Ia-like' antigens on mononuclear cells from various lymphoid organs. They were found almost exclusively on lymphocytes expressing surface immunoglobulin (B lymphocytes) and on a small population of surface immunoglobulin negative cells. Most thymocytes were negative for Class II molecules while thymic epithelial cells were positive. The tissue distribution of Class II molecules was found to be similar to that described in man. Individual monoclonal antibodies displayed no variations in reactivity with the different tissues studied.

Animals↗
PubMed1985

Studies on the distribution of binucleate cells in the placenta of the sheep with a monoclonal antibody SBU-3.

The distribution of cells recognised by the monoclonal antibody SBU-3 raised against trophoblast microvilli during development of the sheep placenta was investigated using the indirect immunoperoxidase technique. At 21 days of gestation, the placental antigen recognised by the monoclonal antibody SBU-3 was observed in the binucleate cells in the trophoblast located in close apposition to the caruncular epithelium. From 30-100 days there was a dramatic increase in the number of SBU-3-positive cells in the placentomal trophoblast and the syncytial layer in the placentome. An insignificant number of SBU-3-positive cells was observed in the interplacentomal trophoblast. By 120-145 days, the syncytial layer became less intensely stained, but strongly SBU-3-positive binucleate cells were still present in the placentomal trophoblast. It is concluded that the antigen recognised by the monoclonal antibody SBU-3 is a secretory product of the binucleate cells of the trophoblast, whose function is at present unknown. The findings in this study are consistent with the theory that the syncytium is formed by fusion of migrating fetal binucleate cells.

Animals↗
PubMed1983

MRC OX-22, a monoclonal antibody that labels a new subset of T lymphocytes and reacts with the high molecular weight form of the leukocyte-common antigen.

A mouse monoclonal antibody (MRC OX-22) is described that labels rat T cells which mediate graft-versus-host reactions and those responsible for the suppression of antibody synthesis in hosts undergoing these reactions. In contrast, most of the T cells that provide help for B cells are MRC OX-22 negative. These results, taken together with those published previously, demonstrate that the rat contains at least three phenotypically and functionally distinct subsets of T cells. The MRC OX-22 antibody also labels all B cells, 50% of bone marrow cells, but only 2% of thymocytes. Of these latter cells about half are found at the edge of the medulla and the remainder are randomly distributed throughout the cortex and medulla. These findings lend support to the view that mature thymocytes leave the thymus at the cortico-medullary junction, and also suggest that both cortex and medulla may be sites where thymocytes mature. Biochemical studies showed that the MRC OX-22 antibody reacts with the high molecular weight form of the leukocyte-common antigen (L-CA). Comparison with data on human L-CA suggests that the molecular and antigenic heterogeneity of this set of glycoproteins has been conserved between rat and man.

Absorption↗
PubMed1982

Purification of human C3b inactivator by monoclonal-antibody affinity chromatography.

Monoclonal antibody has been obtained to the human complement control protein C3b inactivator after immunization of mice with the enzyme prepared by conventional methods. Antibody from ascitic fluid was purified and coupled to Sepharose-CL-4B to give a specific affinity column, which was used to isolate C3b inactivator from human serum in 70% yield. The product was characterized by size, chain structure, amino acid analysis and proteolytic activity.

Amino Acids↗
PubMed1982

An immunological method to determine antigenic variation in three strains of myxoma virus.

A technique is described for the purification of soluble antigens of three strains of myxoma virus. Radioimmunoassays were used to study the antigenic differences between the three strains. Results show that the soluble antigens isolated from Lu and G.V. strains do not cross-react in rabbits tested, suggesting that rabbits infected with Lu and G.V. strains of the myxoma virus can be readily distinguished. Antigen isolated from the U.F.S. strain cross-reacted with sera from both Lu- and G.V.-infected rabbits.

Antigens, Viral↗
PubMed1982

Serological and genetic identification of a bovine B lymphocyte alloantigen system.

A two-colour fluorescence microcytotoxicity test was used to screen antisera for antibodies specific for bovine B lymphocytes. A total of 114 cattle alloantisera were screened against peripheral blood lymphocytes from 100 unrelated individuals. Anti-B lymphocyte activity was detected in 47 antisera. Cytotoxic antibodies to antigens other than B lymphocyte specific antigens were removed by absorbing the antisera with buffy coat cells or platelets isolated from whole blood. Selected antisera were used to type paternal half-sib families. The presence of a polymorphic, MHS-linked antigen system on B lymphocytes was demonstrated. The tissue distribution and MHS linkage of these antigens suggests this system is analogous to the class II or Ia antigens of other species.

Animals↗
PubMed1982

Importance of the liver in immunoglobulin catabolism.

The catabolism of IgG labelled with radioactive iodine was investigated in sheep. The half-life time, fractional catabolic rate and daily loss of radioactivity through the bile were measured. No IgM or IgA were found in sheep bile. The results are discussed in relation to the recent finding that large quantities of oligomeric IgA is excreted in rat bile.

Animals↗
PubMed1981

Destruction of Hassall's corpuscles by macrophages in the sheep thymus.

The dissolution of Hassall's corpuscles by macrophages has been demonstrated in the sheep thymus. The findings indicate that enlarged Hassall's corpuscles are rapidly broken down by macrophages at the end of gestation or immediately after birth and replaced by newly formed corpuscles, and that these cyclic changes in Hassall's corpuscles persist, under normal physiological conditions, throughout life.

Animals↗
PubMed1981

Allogeneic antibody response in cattle.

Antibody responses following immunization with allogeneic bovine lymphocytes, goose red blood cells (GRBC), and ovalbumin (given IV) were studied in 20 heifers. Antibody to GRBC was detectable by 4 to 9 days in all heifers and followed the characteristic pattern of a low-titer primary response which was predominantly immunoglobulin (Ig) M, whereas a high titer IgG secondary response was observed. The dose of ovalbumin used failed to elicit a detectable antibody response. An immune response to allogeneic lymphocytes was observed, but it differed from the GRBC response. Cytotoxic antibody directed against lymphocytes was detectable by day 14 in 5 of the heifers. Five others responded by days 17 to 24 after secondary immunization. The responses were of low titer and predominantly IgM, after both primary and secondary immunizations. The time of antibody appearance and titers varied between heifers and was not dependent on differences at the major histocompatibility complex (BoLA) between heifers and immunizing lymphocytes. Cytotoxic antibody reacted with both B and T lymphocytes and appeared to recognize the serologically defined BoLA antigens. Noncytotoxic alloantibody was detected in the serum of 1 heifer and appeared to be directed against a subpopulation of lymphocytes, possibly those bearing Ia-like antigens.

Animals↗
PubMed1980

The catabolism of alloantibody IgG2a in normal and homograft tolerant rats.

Alloantibody was raised in PVG/c rats against DA rats. The catabolism of alloantibody in normal PVG/c rats and PVG/c rats tolerant to DA rats was followed after intravenous injection. A haemagglutination assay was used to detect alloantibody activity. The half-life time of alloantibody IgG2a in the normal PVG/c rats was 10 days. On the other hand, in the PVG/c rats tolerant to DA rats, the half-life of alloantibody IgG2a varied. The rats could be divided into three groups. Group A: alloantibody IgG2a was eliminated from the circulation very rapidly. Group B: alloantibody IgG2a disappeared from the circulation relatively rapidly and was maintained at a low level in the plasma but then increased to a high titre. This peculiar pattern of Group B seems to be due to the endogenous production of alloantibody. In this case abrogation of tolerance took place. Group C: the pattern of elimination of this group was almost identical to that of normal rats. The biological significance of the plasma decay of alloantibody IgG2a in the normal and homograft tolerant rats has been considered. It is concluded from the present results that alloantibody might be important in some cases for the maintenance of homograft tolerance.

Animals↗
PubMed1979

Thymus and the endocrine system: ovarian dysgenesis in neonatally thymectomized rats.

By 10 days after neonatal thymectomy, the areas of lymphocytic depletion were being repopulated by plasma or reticular cells. Subsequently, ovarian dysgenesis was observed in 50-day-old thymectomized female rats as hyperplasia of ovarian interstitial cells an an enhanced degeneration of follicles. Thymectomized rats at 130 and 170 days of age showed complete ovarian dysgenesis, testicular atrophy, hypertrophy of pituitary beta-cells with pronounced cytoplasmic haloes, and lymphocytic infiltration in the pituitary, thyroid and prostate glands. These results suggest that neonatal thymectomy may initially influence the lymphoid organs (i.e. the immune system) and that changes in the immune system may result in the autoimmune-like damage in the endocrine organs and the prostate gland. Associated with these changes, the concentrations of plasma progesterone and 17 alpha-hydroxyprogesterone were significantly reduced in 130-day-old thymectomized female rats with respect to the sham-thymectomized controls. The concentration of plasma oestradiol-17 beta in thymectomized female rats was the same as in sham-thymectomized female rats. These results suggest that gestagens may normally suppress immune responses but that, in the case of thymectomized female rats, the reduced levels of gestagens may lead to enhanced immune responses.

Animals↗
PubMed1978

Synthesis of immunoglobulin by normal and antigenically stimulated fetal sheep.

The rate of appearance, quantity and immunochemical character of serum immunoglobulins which appear normally during the development of fetal sheep and following the injection of antigens at different stages of gestation have been studied. After 70 days' gestation a percentage of normal fetal sheep synthesise IgM. Although the concentration of IgM in the circulation of these animals was very low, the precentage with IgM increased with fetal age. A few late term fetuses were detected which also had IgG1 in their circulation, although none were detected with IgG2 or IgA. Fetuses injected with antigens before 71 days' gestation only synthesised IgM, while fetuses injected after 79 days' gestation synthesised both IgM and IgG1. Neither IgG2 nor IgA were detected by single-radial immunodiffusion analyses during the first 14 days of primary immune responses to a variety of antigens, although trace amounts of IgG2 were detected late in responses occurring in older fetuses. The immunoglobulins synthesised by antigenically stimulated fetal sheep appeared identical to adult sheep 19S IgM, 7S IgG1 and 7S IgG2 respectively, when analysed by immunoelectrophoresis, isoelectric focusing and G200 Sephadex column chromatography.

Adjuvants, Immunologic↗
PubMed1976

The thyroxine-binding properties of rat and rabbit serum proteins.

The thyroxine (T4) binding properties of rat and rabbit serum proteins were studied using a gel equilibration technique, gel filtration and polyacrylamide gel electrophoresis. In both species two different T4 binding molecules were identified in whole serum and in Cohn fraction V preparations. Only one of these binding species demonstrated the characteristics of specific binding, i.e., high affinity for the hormone and binding site saturability. The mean (+/- SD) apparent association constants (ka) at 37 C for the specific binding proteins in whole rat and rabbit serum were 3.5 +/- 0.5 x 10(8)M-1 and 2.8 +/- 0.5 x 10(8)M-1, respectively. The mean T4 binding capacities of these proteins were 4.3 +/- 1.2 x 10(-6)M and 7.4 +/- 1.0 x 10(-6)M for rat and rabbit serum, respectively. Non-specific binding was due to serum albumin. Rat albumin (ka = 6.1 +/- 1.6 x 10(5)M-1, at 37 C) bound T4 significantly more strongly than did rabbit albumin (ka = 2.3 +/- 0.4 x 10(5)M-1, at 37 C) when it was assumed that there was only one T4 binding site/molecule of albumin. The ability of rat albumin to bind more T4 could also be explained by a greater number of T4 binding sites/molecule. Partial separation of the two T4 binding species was attained by gel filtration on Sephadex G200 columns. The specific binding protein of both rat and rabbit serum was eluted slightly later than the corresponding serum albumin. Polyacrylamide gel electrophoresis resulted in the separation of two distinct T4 binding peaks in the rat, but with rabbit serum clear separation of the two T4 binding molecules was not attained. In both species the specific binding protein migrated anodal to serum albumin.

Alpha-Globulins↗
PubMed1976

Effect of fetal thymectomy on IgG, IgM, and IgA concentrations in sheep.

Serum concentrations of immunoglobulins (Ig) IgG, IgG, IgM, and IgA were compared for normal and thymectomized lambs. Fetal thymectomies were performed in utero from 55 to 67 days of gestation. High serum IgG, IgM, and IgA concentrations occurred in all lambs after they ingested colostrum; however, the concentration of these Ig, as measured by single radial immunodiffusion, decreased exponentially during the first 16 days after birth. The half-life values for IgG, IgM, and IgA during this period in both normal and thymectomized lambs were about 25, 6, and 2 days, respectively. Increasing amounts of IgG were not detected in the serums of either group until 1 month of age. At 64 to 128 days, significantly smaller quantities of IgG and IgG were found in thymectomized lambs, whereas concentrations of IgA and IgM were similar in both groups. The results indicate that the thymus may regulate production of IgG in sheep.

Animals↗
PubMed1975

The effect of pre-partum milking on the transfer of immunoglobulin into mammary secretion of cows.

The significance of local effects associated with mammary involution on transfer of immunoglobulin and especially on the selective transfer of IgG1 into mammary secretion of cows approaching parturition has been determined. This was carried out by measuring the changes in the concentration of IgG1, IgG2, IgM and IgA in serum and mammary secretion of 5 cows in which two mammary glands were milked continuously (twice daily) during the period preceding parturition, while the other two glands were allowed to undergo normal involution. In the secretion of unmilked glands of all cows there was a substantial increase in the concentration of IgG1 as cows approached parturition. In contrast, the increases in the concentration of IgG1 and in the selective index for IgG1 of milked glands were either virtually non-existent (1 cow) or generally reduced in magnitude and delayed in time of onset (4 cows). It is clear from the results that continued milking of a mammary gland throughout pregnancy tends to maintain milk production in the milked gland and at the same time reduces the massive selective transfer of IgG1 into secretion of that gland.

Animals↗