Immunology Today, Vol. d, .No. 2, 1983
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19 Subbarao, B., Mosier, D. E., Ahmed, A., Mond, J. J., Scher, I. and Paul, W. E. (1979)`7. Exp. Med. 149, 495 20 Mond, J. J., Lieberman, R., Inman, J. K., Mosier, D. E. and Paul, W. E. (1977),7. Exp. Med. 146, 1138 21 Boswell, H. S., Ahmed, A., Scher, I. and Singer, A. (1980) J. Immunol. 125, 1340 22 Singer, A., Asano, Y., Shigeta, M., Hathcock, K. S., Ahmed, A., Fathman, C. G. and Hodes, R.J. (1982) lmmunol. Rev. 64, 137 23 Perlmutter, R. M., Nahm, M., Stein, K. E., Slack, J., Zitron, 1. M., Paul, W. E. and Davie, J. M. (1979),7. Exp. Med. 149, 993
24 Perlmuner, R. M., Hansburg, D., Briles, D. E., Nicolotti, R. A. and Davie, J. M. (1978).7. lmmunol. 121,566 25 Stein, K., Ahmed, A., Zopf, D. and Paul, W. E (manuscript in preparation) 26 Scher, l., Sharrow, S. O. and Paul, W. E. (1976)J. Exp. Med. 144, 507 27 Metcalf, E. S., Scher, I. and Klinman, N. R. (1980)`7. Exp. Med. 151, 486 28 Mond, J. J., Scher, I., Cossman, J., Kessler, S., Mongini, P. K. A., Housen, C., Finkelman, F. D. and Paul, W. E. (1982) J. Exp. Med. 155, 924
Thymus in vitro John H. Robinson and Reg K. Jordan The establishment of the peripheral T-cell pool is attributed in part to cellular interactions occuring within the developing thymus ~. In embryogenesis the thymus appears as an epithelio-lymphoid rudiment with pharyngeal epithelium acting as a matrix for the differentiation of thymic lymphocytes which develop from a colonizing pool of lympho-haematopoietic cells. In addition to T-cell progenitors, this immigrant haematopoietic component also gives rise to a p.opulation of macrophage-like cells which may have an important contribution to intrathymic lymphopoiesis as they are capable of presenting antigen to peripheral T cells 2. Thus, we see the epithelial cells together with thymic macrophages, and even the lymphocytes themselves, contributing to the specific microenvironment(s) necessary for T-progenitor/precursor differentiation, with cellular interactions between these cell types determining the proliferation and selection of maturing thymocytes. Cell surface M H C gene products as well as soluble factors such as interleukins, may directly induce precursor proliferation while M H C antigens may also act as signals for the selection of thymocytes of relevant specificity. Our approach has been to apply in-vitro techniques in the dissection of embryonic mouse thymus in order to characterize the cellular components and their individual contributions to the thymic microenviroment 3.4.
Why organotypic culture? We have adopted in-vitro methods to further our aims in elucidating the ontogenetic mechanisms involved in thymic lymphopoiesis, as tissue culture methods offer a unique opportunity to overcome many in-situ limitations and in-vivo constraints. In addition, in-vitro models have particular advantages for the dissection and manipulation of cellular interactions in ontogeny. However, a recurring criticism of any study in vitro is the extent to which observations reflect the situation in vivo. While this criticism applies to dissociated cell culture with its inherent bias of selection, we would suggest that the responses of organotypic cultures of foetal mouse thymus are a valid reflection of thymic lymphopoiesis in vivo4-L Department of Anatomy, Medical School, University of Newcastle upon Tyne, Newcastle upon Tyne NE1 7RU, U.K.
Organotypic methods are based on preserving the three-dimensional relationships between interacting cells of a tissue so that morphological architecture and function are maintained in culture. This can be achieved by organ culturing small tissue fragments at a gas-liquid interface, Such organ cultures support the development and differentiation of relatively undifferentiated foetal tissues• It is this approach which has been successfully exploited in studies of thymus, with the mouse being the mammalian species of choice in that embryonic thymus can be removed easily at the stage of initial haematopoietic colonization (12-14 days' gestation), and at this stage an individual thymic lobe is an ideal size (
41
19 Subbarao, B., Mosier, D. E., Ahmed, A., Mond, J. J., Scher, I. and Paul, W. E. (1979)`7. Exp. Med. 149, 495 20 Mond, J. J., Lieberman, R., Inman, J. K., Mosier, D. E. and Paul, W. E. (1977),7. Exp. Med. 146, 1138 21 Boswell, H. S., Ahmed, A., Scher, I. and Singer, A. (1980) J. Immunol. 125, 1340 22 Singer, A., Asano, Y., Shigeta, M., Hathcock, K. S., Ahmed, A., Fathman, C. G. and Hodes, R.J. (1982) lmmunol. Rev. 64, 137 23 Perlmutter, R. M., Nahm, M., Stein, K. E., Slack, J., Zitron, 1. M., Paul, W. E. and Davie, J. M. (1979),7. Exp. Med. 149, 993
24 Perlmuner, R. M., Hansburg, D., Briles, D. E., Nicolotti, R. A. and Davie, J. M. (1978).7. lmmunol. 121,566 25 Stein, K., Ahmed, A., Zopf, D. and Paul, W. E (manuscript in preparation) 26 Scher, l., Sharrow, S. O. and Paul, W. E. (1976)J. Exp. Med. 144, 507 27 Metcalf, E. S., Scher, I. and Klinman, N. R. (1980)`7. Exp. Med. 151, 486 28 Mond, J. J., Scher, I., Cossman, J., Kessler, S., Mongini, P. K. A., Housen, C., Finkelman, F. D. and Paul, W. E. (1982) J. Exp. Med. 155, 924
Thymus in vitro John H. Robinson and Reg K. Jordan The establishment of the peripheral T-cell pool is attributed in part to cellular interactions occuring within the developing thymus ~. In embryogenesis the thymus appears as an epithelio-lymphoid rudiment with pharyngeal epithelium acting as a matrix for the differentiation of thymic lymphocytes which develop from a colonizing pool of lympho-haematopoietic cells. In addition to T-cell progenitors, this immigrant haematopoietic component also gives rise to a p.opulation of macrophage-like cells which may have an important contribution to intrathymic lymphopoiesis as they are capable of presenting antigen to peripheral T cells 2. Thus, we see the epithelial cells together with thymic macrophages, and even the lymphocytes themselves, contributing to the specific microenvironment(s) necessary for T-progenitor/precursor differentiation, with cellular interactions between these cell types determining the proliferation and selection of maturing thymocytes. Cell surface M H C gene products as well as soluble factors such as interleukins, may directly induce precursor proliferation while M H C antigens may also act as signals for the selection of thymocytes of relevant specificity. Our approach has been to apply in-vitro techniques in the dissection of embryonic mouse thymus in order to characterize the cellular components and their individual contributions to the thymic microenviroment 3.4.
Why organotypic culture? We have adopted in-vitro methods to further our aims in elucidating the ontogenetic mechanisms involved in thymic lymphopoiesis, as tissue culture methods offer a unique opportunity to overcome many in-situ limitations and in-vivo constraints. In addition, in-vitro models have particular advantages for the dissection and manipulation of cellular interactions in ontogeny. However, a recurring criticism of any study in vitro is the extent to which observations reflect the situation in vivo. While this criticism applies to dissociated cell culture with its inherent bias of selection, we would suggest that the responses of organotypic cultures of foetal mouse thymus are a valid reflection of thymic lymphopoiesis in vivo4-L Department of Anatomy, Medical School, University of Newcastle upon Tyne, Newcastle upon Tyne NE1 7RU, U.K.
Organotypic methods are based on preserving the three-dimensional relationships between interacting cells of a tissue so that morphological architecture and function are maintained in culture. This can be achieved by organ culturing small tissue fragments at a gas-liquid interface, Such organ cultures support the development and differentiation of relatively undifferentiated foetal tissues• It is this approach which has been successfully exploited in studies of thymus, with the mouse being the mammalian species of choice in that embryonic thymus can be removed easily at the stage of initial haematopoietic colonization (12-14 days' gestation), and at this stage an individual thymic lobe is an ideal size (
