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H A Ward

Publications and source records attributed to H A Ward.

At least 37 records · Page 2Linked to original sources
PubMed1984

Lymphoid antigenic determinants of the chicken: ontogeny of bursa-dependent lymphoid tissue.

The ontogenic development of the bursa-dependent lymphoid tissue in the chicken has been studied using rabbit antisera specific for B lymphocyte sub-populations and two elements of the bursal microenvironment. The antigens investigated were: the chicken B lymphocyte antigen ( CBLA ); mature B lymphocyte antigen ( CMBLA ); a foetal-associated antigen ( CFAA ) present on embryonic haemopoietic cells and adult bone marrow and bursa cells; immunoglobulin (Ig) and IgG; a bursa-specific cortical reticulin fibre antigen ( CBRFA ); a gut-associated mucin antigen ( CGAMA ) present on bursal medullary reticular epithelial (REp) cells. The development of suspected precursor cells was examined using a rabbit antiserum specific for foetal spleen cells. The major finding was the interrelationship between developing B cells and the bursal microenvironment. The first CBLA - and CFAA -positive cells were detected in the bursa at day 8 of incubation but their precise localization was difficult to assess. In 12-15 day embryos, both these cells were found predominantly in the tunica-propria in close proximity to cells bearing the reticulin fibre antigen CBRFA . This close association between CBLA -, CFAA - and CBRFA determinants represents the earliest stages of B cell differentiation and mimics that found in the adult bursa cortex. By day 18, the majority of bursa cells expressed CBLA and Ig and were localized in the developing medullary follicles, the REp cells of which were CGAMA -positive, demonstrating a very early interaction between intestinal tract contents, bursal REp cells and B cell maturation. Around hatching some bursa cells showed a marked increase in the membrane expression of CBLA and Ig, and the simultaneous expression of CMBLA and IgG. These cells were present in medullary follicles; CBRFA was present on cortical reticulin fibres which provided a supporting framework for the more immature CFAA -positive cells.

Animals↗
PubMed1983

Bursal and thymic reticular epithelial cells in the chicken: induction of B- and T-lymphocyte differentiation by in vitro monolayer cultures.

The role of chicken bursal and thymic reticular epithelial cells (REp cells) in the induction of B- and T-lymphocyte differentiation has been investigated using in vitro culture of these cells. Splenic adherent cells were used as controls. Precursor populations were obtained predominantly from embryonic bone marrow or spleen and incubated with REp cell monolayers for 72 hr. Differentiation was assessed by the expression of specific membrane antigens: chicken B lymphocyte-specific antigen (CBLA) and chicken T lymphocyte-specific antigen (CTLA). Bursal REp cells specifically induced approximately 20-30% of the embryonic cells to express CBLA but had no influence on CTLA expression. Conversely, CTLA, but not CBLA, was induced in approximately 20% of the embryonic cells by the thymic REp cell cultures. No effect on the expression of either antigen was observed with the splenic adherent cells. The induced cells correspond to the first stage of B- and T-lymphocyte differentiation found in vivo. The assay system also facilitated the study of shifts in precursor content of various organs with development. Whereas embryonic bone marrow of all ages studied contained both B- and T-lymphocyte precursors, these were not demonstrable in donors after hatching. Use of 12-day embryonic bursa and thymus suspensions as sources of stem cells indicated that precommitment to the B- or T-lymphocyte lineage is irreversible.

Aging↗
PubMed1983

Bursal and thymic reticular epithelial cells in the chicken: preparation of in vitro monolayer cultures.

To study the nature of reticular epithelial (REp) cells and their role in the specific microenvironments of the chicken bursa and thymus, a method was developed for the in vitro culture of purified preparations of these cells. For comparison, similar cultures of splenic adherent cells were also performed. REp cell-rich bursa medullary follicles and mildly trypsinized thymic fragments were X-irradiated (850 rad) to eliminate remaining lymphocytes and transferred to culture flasks. In bursal cultures, after 2-4 days incubation the basement membrane (BM) encapsulating the follicles disrupted and the immediately underlying epithelial cells grew out as a monolayer. By 10 days, REp cells at the periphery developed cytoplasmic processes; occasionally these cells appeared to "bud-off" and grow as isolated dendritic cells. Thymic REp cells were generally slower to proliferate but formed a monolayer by 10-14 days. Splenic adherent cells developed extensive growth within 4 days. REp cells were distinguished from fibroblasts, when present, morphologically and by their limited phagocytic ability. The former were also periodic acid-Sciffs reagent (PAS)-positive and produced reticulin granules. Bursal REp cells were also positive for a gut-associated mucin, but this may have been bound in vivo prior to culture. Neither T nor B lymphocyte-specific antigens were detectable on the cultured REp cells or splenic adherent cells, but they were all rich in cytoplasmic actin. A major feature of REp cells to emerge in this study was the obvious presence of subpopulations of these cells, which raises important questions as to their exact nature and lineage. The accompanying paper details the ability of the bursal and thymic REp cell cultures to induce B-or T-lymphocyte differentiation, respectively, in vitro.

Animals↗
PubMed1982

Purification and chemical characterisation of membrane glycoproteins from rat thymocytes and brain, recognised by monoclonal antibody MRC OX 2.

The MRC OX 2 monoclonal antibody recognises antigens present on rat thymocytes, brain, follicular dendritic cells in lymphoid organs, vascular endothelium, some smooth muscle and B-lymphocytes. The OX 2 antigens recognised by this antibody were purified from brain and thymus, by solubilisation with sodium deoxycholate, affinity chromatography with MRC OX 2 antibody and gel filtration. The purified brain and thymocyte OX 2 antigens were glycoproteins with apparent Mr 41000 and 47000 respectively as determined by polyacrylamide gel electrophoresis in sodium dodecyl sulphate. Rabbit antisera raised against the purified antigens were analysed by radioimmunoassay and immunoperoxidase-staining of tissue sections. The brain and thymocyte OX 2 antigens were antigenically very similar to those on the other tissues. This indicates that the unusual pattern of distribution was not the result of fortuitous cross-reaction of the MRC OX 2 antibody, as the rabbit sera would be expected to recognise more determinants on the antigen than that recognised by the monoclonal antibody. The amino acid compositions of brain and thymus OX 2 antigens were very similar but with no distinguishing features. Carbohydrate compositions showed that the OX 2 antigens were highly glycosylated, with brain OX 2 antigen containing 24% and thymocyte OX 2 antigen 33% by weight of carbohydrate. Both OX 2 antigens contained carbohydrate residues typical of structures N-linked to asparagine but lacked galactosamine, indicating the absence of O-linked structures. Thymocyte OX 2 contained higher levels of galactose and sialic acid but less fucose than brain OX 2. Similar differences had been observed for brain and thymocyte Thy-1 antigens and were also observed in pooled glycoproteins purified by lentil affinity chromatography from these tissues, reflecting overall differences in the patterns of glycosylation in the two tissues. The OX 2 antigens showed many similarities to Thy-1 antigens in their odd patterns of distribution, characteristic migration on polyacrylamide gels in sodium dodecyl sulphate, and carbohydrate compositions. It is possible that OX 2 antigens, like Thy-1 antigens, have homologies with immunoglobulin domains. A possible role for OX 2 antigens in cell interactions necessary for tissue organisation is discussed.

Amino Acids↗
PubMed1982

Persistence of organ- and iso-antigens in vitro in a long-term culture cell line of colonic carcinoma.

Cells of colonic carcinoma line HT-29, cultured over more than 170 generations and extensively used in immunological studies of patients with colorectal tumours, still express several immunologically valuable characteristics presumably present since its inception. The cell line can induce a poorly differentiated adenocarcinoma in the nude mouse, it has human antigenic characteristics, it expresses blood group A antigen, and produces a colon-specific mucin and CEA, though not colon cancer-specific mucin (CCM). It remains useful as a target for in vitro testing of anti-tumour immunoreactivity in colorectal cancer patients.

Adenocarcinoma↗
PubMed1980

Immunohistological patterns of carcinoembryonic antigen in colorectal carcinoma. Correlation with staging and blood levels.

Forty-four primary adenocarcinomas of the large bowel and 2 liver metastases were stained for carcinoembryonic antigen (CEA) in tissue sections by indirect immunofluorescence. All tumours were positive and showed either one or more of 3 different patterns--luminal; linear at surface of the tumour cells; cytoplasmic. In most cases (83%), two or all 3 patterns were seen in the same or in different parts of a tumour. The immunohistological staining was concordant with preoperative blood levels of CEA in 31 cases (67%) in that 26 tumours showed strong immunofluorescence associated with blood CEA above 2.5 micrograms/l, and 5 showed weak staining and blood CEA values less than 2.5 micrograms/l. However, in 7 strong staining was associated with low blood CEA, and in 8 weak staining was associated with high blood levels. The dissociation between histological and blood CEA findings in 1/3 of the cases, together with the marked variation within the same tumour and differences between one of the primaries and its liver recurrence, suggest that CEA immunohistology is of no better prognostic value than blood CEA levels. There was no association between CEA immunohistology and tumour staging or differentiation. However, blood CEA levels were significantly higher in tumours with extensive local or distant spread (stage D) and in poorly differentiated tumours.

Adenocarcinoma↗
PubMed1979

Detection of early lymphocyte activation by the fluorescent cell membrane probe N-phenyl-1-naphthylamine.

N-phenyl-1-naphthylamine (NPN) becomes fluorescent after binding to hydrophobic regions of cell membranes. Rat and mouse lymphoid cell suspensions stained with NPN showed changes in fluorescence emission 30 min after stimulation with mitogen or antigen, detected by microfluorimetry. Incubation of NPN-labelled mouse and rat thymocytes with phytohaemagglutinin or concanavalin A (Con A) caused an increase in mean cell fluorescence intensity. The response to Con A was inhibited by sodium azide and alpha-methyl mannoside. Stimulation of spleen cells from mice by allogeneic cells, or from tumour-bearing rats by tumour antigen consistently resulted in decreased fluorescence. The 'mixed lymphocyte response' detected only certain genetic differences between mouse strains and was proportional to the ratio of stimulator to responder cell number. The NPN staining procedure offers a simple and rapid assay of immunoreactivity and a means of studying early subcellular changes following lymphocyte activation.

1-Naphthylamine↗
PubMed1979

Immunoassays.

Explore the source record for details and available documents.

Enzyme-Linked Immunosorbent Assay↗
PubMed1979

Rhodamine as a fluorescent probe of lymphocyte activation.

Fresh rat and mouse lymphoid cells have been labelled by stable linkage with tetramethylrhodamine isothiocyanate (TMRITC). A change in intensity, either an increase or decrease of the fluorescent emission of the cells, detected by microfluorimetry, was induced by mitogen stimulation or the mixed lymphocyte reaction. The change in fluorescence was observed within 3 h of mitogen stimulation and within 0.5 h in the mixed lymphocyte test. These early cellular responses were detectable consistently whether the labelling was done before or after mitogen stimulation; post-labelling only was studied in the mixed lymphocyte reaction. The method should provide a time-saving practical procedure for early detection of the lymphoid cell responses and would readily lend itself to flow cytofluorimetry for possible routine diagnostic use.

Animals↗
PubMed1978

Lymphoid antigenic determinants of the chicken. Cellular representation and tissue localization.

Antisera were prepared against a variety of chicken tissues with a view to detecting antigens specific for subpopulations of T and B cells at different maturation stages. By appropriate absorption analysis, the following antigens were defined: (a) thymus organ-specific antigen (CTOA); (b) T lymphocyte-specific antigen (CTLA); (c) B lymphocyte-specific antigen (CBLA); (d) mature B lymphocyte-specific antigen (CMBLA); (e) a foetal-associated antigen (CFAA) present on embryonic haemopoietic cells, and adult bone marrow and immature bursa cells, suggesting the cell types concerned may be at an early stage of development, possibly including precursors. For comparison with the above antigens, cells were also examined for surface Ig and IgG. T cells were found in periarteriolar sheaths in the spleen, and predominantly in the sub-epithelium and sub-mucosa of the caecal tonsil of the gut-associated lymphoid tissue (GALT). B cells were localized in periellipsoidal sheaths and germinal centres in the spleen, and in primary follicles or germinal centres in the GALT. The thymic and bursal medullas contained the mature populations of T and B lymphocytes respectively.

Animals↗
PubMed1976

Antiserum specific for reticulin of the bursa of fabricius.

Antiserum produced by immunizing rabbits with embryonic chicken spleen cells showed, after appropriate absorption with cell suspensions, specificity for fetal spleen cells in membrane immunofluorescence tests. However, when the original antiserum was absorbed with tissue homogenates and tested on cryostat tissue sections, it reacted specifically with the reticular framework which separates the cortical and medullary lymphocytes in the follicles of the adult bursa of Fabricius. It is suggested that the reticulin may influence bursal lymphoid differentiation.

Animals↗