The major objective of this proposal is to test the """"""""dual T cell system"""""""" hypothesis, which proposes that the thymus functions as a compound organ to process 2 sets of thymocyte progenitors and to produce 2 lineages of T cells, one from thymus cortex and one from thymus medulla. This hypothesis derives primarily from our description of TdT plus TdT minus subsets of prothymocytes and of antigenically discrete subsets of thymocytes and T cells in rat and mouse. The ability to test this hypothesis has been enhanced by our finding that Thy-1 antigen is a selective marker for immature lymphohemopoietic cells in the rat, and by our use of the fluorescence-activated cell sorter (FACS) to isolated pluripotent hemopoietic stem cells (HSC) (75% purity) and TdT plus thymocyte progenitors (85% purity) from rat bone marrow.
Our specific aims are to completely purify pluriopotent hemopoietic stem cells; to determine whether a common stem cell exists for T and B lymphocytes; to purify the TdT subset of thymocytes progenitors; to isolate the presumptive precursors of cortical and medullary thymocytes from the subcapsular region of the thymus and to purify the Thy-1 plus and Thy-1 minus subsets of rat T cells for further functional studies. The major experimental approach will be through the use of the fluorescence-activated cell sorter in concert with antisera to a variety of cell surface differentiation antigens. Additionally we plan a series of experiments on B cell ontogeny, based on observation that in the rat Thy-1 antigen is present on B cells only during the antigen independent phase of development. Using the FACS to separate immature subsets of the B cell lineage we propose to determine whether a discrete progenitor for B lymphocytes exists, and the stages in development at which B cells become readily tolerizable, and at which they first can be stimulated by antigen to generate antibody-forming cells. Our ultimate goal is to test the developmental and functional potential of these purified cell subsets using in vivo and in vitro cloning systems to gain a more comprehensive view of the organization of the lymphocyte system and the factors which control its development and function.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Immunological Sciences Study Section (IMS)
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University of Connecticut
Schools of Dentistry
United States
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McKenna, S D; Medlock, E S; Greiner, D L et al. (1994) A selective culture system for generating terminal deoxynucleotidyl transferase-positive lymphoid precursor cells in vitro. IV. Properties and developmental relationships of the lymphoid cells in the adherent and nonadherent compartments of the culture. Exp Hematol 22:1164-70
Hosseinzadeh, H; Goldschneider, I (1993) Recent thymic emigrants in the rat express a unique antigenic phenotype and undergo post-thymic maturation in peripheral lymphoid tissues. J Immunol 150:1670-9
McKenna, S D; Goldschneider, I (1993) A selective culture system for generating terminal deoxynucleotidyl transferase-positive lymphoid cells in vitro. V. Detection of stage-specific pro-B-cell stimulating activity in medium conditioned by mouse bone marrow stromal cells. Dev Immunol 3:181-95
Medlock, E S; McKenna, S D; Goldschneider, I (1993) A selective culture system for generating terminal deoxynucleotidyl transferase-positive lymphoid cells in vitro. III. Structure of the bone marrow microenvironment for early lymphopoiesis. Lab Invest 69:616-28
Zadeh, H H; Goldschneider, I (1993) Demonstration of large-scale migration of cortical thymocytes to peripheral lymphoid tissues in cyclosporin A-treated rats. J Exp Med 178:285-93
Donskoy, E; Goldschneider, I (1992) Thymocytopoiesis is maintained by blood-borne precursors throughout postnatal life. A study in parabiotic mice. J Immunol 148:1604-12
Mojcik, C F; Greiner, D L; Goldschneider, I (1991) Characterization of RT6-bearing rat lymphocytes. II. Developmental relationships of RT6- and RT6+ T cells. Dev Immunol 1:191-201
Goldschneider, I; Hosseinzadeh, H; Chen-Woan, M (1991) Short-term treatment of rats with cyclosporin A causes the appearance of lymph node T cells that resemble cortical thymocytes. Transplant Proc 23:122-5
Chen-Woan, M; Goldschneider, I (1991) Evidence that cyclosporine treatment causes the appearance in rat lymph node of T cells having the antigenic phenotypes of cortical thymocytes. Transplantation 51:661-8