Partial characterization of a familial B lymphosarcoma with a thymic localization in cattle.

We recently described an original epidemiological form of bovine leukosis in cattle. In the young female offspring of one bull, more than 3% of animals developed a thymic lymphoblastic lymphosarcoma. Of these, 31 cases, together with a lymphoid cell line established from one of the tumours, were phenotypically characterized. Characterization was done using a large combination of well clustered monoclonal antibodies, and monoclonal antibodies prepared in our laboratory by immunizing mice either with bovine normal lymphocytes or with tumour thymic cells. The thymic tumours and the cell line did not express any T lymphoid antigens but they did express some B lymphoid markers. The phenotype of the tumour cells was CD45+/-, CD44+/- TdT+, class II-DR+/-, CD19+/-, CD21-, Ig- and HBM 57+ (recognizing the mb-1 chains of the B-cell receptor). The cell line expressed a more mature phenotype: TdT-, CD45-, CD44+, class II-DR+, CD19+, CD21+/- and sIgG+. These results allow us to consider these tumours as B-cell derived. These B lymphosarcomas with a thymic localization are reminiscent of a human mediastinal non-lymphoblastic lymphoma reported as a primary mediastinal clear cell lymphoma. The possibility of a thymic or extrathymic origin for this B lymphosarcoma is discussed.

Epidemiological and pathological studies of a familial thymic lymphosarcoma in bovine species.

A total of 216 cases of the thymic form of bovine leukosis were observed in Holstein calves in several departments of France over a period of 18 months. Almost all of these calves were sired by the same bull. The calves were negative for bovine leukemia virus-specific antibodies. Morphological studies, including light and electron microscopic cytology, and immunophenotyping were performed in 38 cases. The tumor cells exhibit membrane markers (T-cell antigens) at variable levels, which indicate that they are T-lymphoid derived. The cells are maintained at a very early stage of differentiation as indicated by TdT enzyme activity and the presence of MHC class II antigen.

Preparation and characterization of a monoclonal antibody against bovine CD5 lymphocyte surface antigen.

The M1 monoclonal antibody (mAb) was proved to recognize 51-70% of Bovine peripheral blood lymphocytes (PBL). The M1+ cells were SIg-. In spleen and lymph nodes, the M1 positive lymphocytes were located within the T cell areas. All the lymphoid follicles remained negative. In the thymus, 10% of thymocytes were M1+, most of them were located in the medulla. The M1 mAb did not inhibit spontaneous rosette formation by sheep erythrocytes and bovine lymphocytes. On the other hand, biochemical analysis of membrane antigen with bovine thymic tumor cell line LB203 gave a molecular weight of 75 kDa. Despite a slight difference in biochemical results (75 vs 67-69 kDa). Our data permit us to consider M1 mAb as a possible homologous of human anti-CD5 mAb. Finally, M1 cross-reacted with sheep peripheral blood T lymphocytes.

The BLV-induced leukemia--lymphosarcoma complex in sheep.

Sheep are highly susceptible to BLV infection and can be infected via several different means (routes). In all inoculated animals, specific anti-BLV antibodies can be demonstrated 1 to 3 months post-inoculation (p.i.). Between 10 and 13 months p.i., a moderate but persistent lymphocytosis (PL) may be detected in about 50% of the infected animals. This hematological disorder may be, but is not necessarily, associated with the development of a lymphosarcoma and can (might) be interpreted as a true lymphoid leukemia. According to findings revealed by immunolabelling and mitogen stimulation of peripheral blood lymphocytes, BLV-induced PL appears to be a B-cell disorder. Induced lymphosarcoma appears in about 40% of infected sheep during the 6 years p.i. It too is of B-lymphocyte lineage. In vitro studies demonstrate that BLV antigen is expressed exclusively in B-lymphocytes. Yet, BLV expression is greatly stimulated in whole lymphocyte culture by the addition of T-cell mitogen. This same phenomenon occurs when the supernatant of stimulated T-lymphocyte cultures is added to isolated BLV-infected B-lymphocytes. This observation supports the hypothesis that, as is the case with other retroviruses such as HIV, BLV is able to use the regular activation machinery of the immune system for its own replication and transmission. It seems, therefore, that the leukemia-lymphoma complex in sheep may serve as an accurate experimental model for the study of the biological properties of retroviruses.

Preliminary report of familial thymic lymphosarcoma in Holstein calves.

Seventy-three cases of the thymic form of leukosis were found in Holstein calves in five departments of France over a period of five months. Most of the calves had been sired by the same bull. The calves were negative for specific antibodies to bovine leukaemia virus. Morphological studies including light and electron-microscopic cytology, and serological and virological studies of 14 of the cases suggest that the disease was transmitted genetically.

Development of leukemia and lymphosarcoma induced by bovine leukemia virus in sheep: a hematopathological study.

The hematological and neoplastic disorders induced in sheep by experimental bovine leukemia virus (BLV) infection are described. Seventeen of 19 BLV-inoculated sheep developed a marked increase in peripheral blood lymphocytes by 36 months after the intraperitoneal injection of peripheral blood lymphocytes from a BLV-infected cow. This increase correlated with an increase in the number of circulating B lymphocytes as demonstrated by the presence of surface immunoglobulins (SIg) and a high cell proliferative response to lipopolysaccharide and was considered to be a persistent B cell lymphocytosis. Lymphosarcoma developed in five BLV-infected sheep between 19 and 38 months postinoculation and was preceded in four out of five of these cases by an elevation in peripheral blood lymphocytes which began 4 to 26 months before death due to lymphosarcoma. The majority of tumor cells in all lymphosarcoma cases were of the centroblastic type, and in two cases in which the presence of SIg was assayed, the majority of tumor cells were SIg-positive. Thus, BLV-induced lymphosarcoma in sheep seems to be a B lymphocyte-derived tumor.

Wheat germ agglutinin (WGA): a bovine T lymphocyte marker.

Bovine peripheral blood lymphocytes (PBL) were examined for their ability to bind wheat germ agglutinin (WGA). This lectin labelled 43.8% +/- 11.95 of bovine PBL, whereas peanut agglutinin (PNA), a T cell marker, bound 59.4% +/- 8.67 cells, and surface immunoglobulin (SLG)-bearing cells constituted 24.15% +/- 8.47 of PBL. After panning fractionation of B (Slg+) and T (PNA+) lymphocytes. WGA labelled 89 to 97% of the enriched T cell population (80/87% PNA+; 2-4% Slg+) but only 6 to 8% of the enriched B cell population (85-91% Slg+; 5-7% PNA+).

Selective tropism of bovine leukemia virus (BLV) for surface immunoglobulin-bearing ovine B lymphocytes.

Bovine leukemia virus (BLV) is experimentally infectious for sheep. Virus production does not occur in the animals, but only after in vitro cultivation of infected lymphocytes in the presence of phytohemagglutinin. Lipopolysaccharide or dextran sulfate 500 had no effect. After panning separation, it was possible to demonstrate that, in peripheral blood lymphocytes, BLV was integrated in the B lymphocytes only and that BLV expression took place in a fraction of this population. The ovine leukemia may constitute a good experimental model for understanding the virus-induced leukemias of the BLV-human T cell leukemia virus group.

[Lymphocyte markers in domestic animals. I. Mitogenic lectins and non-mitogenic lectins]. / Les marqueurs lymphocytaires chez les animaux domestiques--I. Lectines mitogènes et lectines non mitogènes.

The authors reviewed the lymphocyte markers in domestic animals. The first part is devoted to lectins. The general and methodologic aspects of lectins as mitogens are studied. The main mitogen lectins are emphasized in regard to their field of utilisation and the technical aspect of their use. The non-mitogen lectins are presented for cell suspension or tissue section staining.

T and B peripheral blood lymphocytes in normal and lymphocytotic sheep.

Surface immunoglobulins (SIg), Peanut Agglutinin (PNA), spontaneous erythrocyte rosette (E-rosette) and Helix pomatia (HP) marker were investigated in normal and Bovine leukemia virus (BLV)-infected sheep. In normal sheep, 19.3% +/- 4.9 of peripheral blood lymphocytes (PBL) were SIg+, whereas 58% +/- 5.69 were PNA+, and 19.6 +/- 5.2 were E-rosette forming cells (E-RFC). In BLV-induced lymphocytotic sheep, SIg+ cells in PBL reached 59.4% +/- 15.06. In the same animals, PNA bound to 20.6% +/- 9.69 and E-RFC were 8.7% +/- 4.5. A panning technique was applied with an anti sheep-immunoglobulins coated plates to separate SIg+ (adherent cells = A) and SIg- cells (non-adherent cells = NA). The (A) population was 94-95% SIg+ cells and 2-3% PNA+, while the (NA) population was 0-4% SIg+ and 79-85% PNA+ cells. Thus PNA is a T cell marker in sheep species. HP, a marker for bovine T lymphocytes was also studied. Sheep PBL do not bind to HP. However, after panning separation about 50% of NA cells became HP+.

Bovine leukemia virus replicates in sheep B lymphocytes under a T cell released factor.

In order to determine which cell supports BLV replication in experimentally infected sheep, peripheral blood lymphocytes (PBL) were separated into purified B and T populations by a panning technique. Our data demonstrate that viral replication takes place only in B lymphocytes. However, PHA, a T cell mitogen, is necessary for BLV replication both in PBL and enriched surface immunoglobulin bearing cells, whereas B cell mitogens have no effect on viral replication. Altogether, these results suggest that BLV activation in enriched B lymphocytes is dependent on the presence of residual T cells, and occurs through a T cell interaction, probably mediated by a soluble factor. This possibility was confirmed by the fact that the conditioned medium from cultures of BLV-free sheep T lymphocytes greatly enhances viral production by infected B lymphocytes. Our data favor the hypothesis that BLV multiplication occurs through the regular activation mechanisms of the immune system.

[Demonstration of the expression of bovine leukemogenic virus (BLV) in sheep lymphocytes by an immunofluorescence technic using monoclonal antibodies]. / Mise en évidence de l'expression du virus leucémogène bovin (BLV) dans les lymphocytes de mouton par une technique d'immunofluorescence utilisant des anticorps monoclonaux.

An indirect immunofluorescence (IF) test was developed to detect bovine leukemia virus (BLV) antigen expression in infected sheep lymphocytes, using monoclonal antibodies anti BLV-major envelope glycoprotein gp51. Peripheral blood lymphocytes were cultivated for 48 h in presence of phytohemagglutinin (PHA) (50 micrograms/ml), and then fixed with acetone. The cells were assayed for the IF test. All experimentally infected sheep were positive with this test.