Transplantation of Cultured Thymic Fragments I. Morphologic and Technical Considerations

Abstract

Thymic fragments were maintained in organ culture until egress or deterioration of the leucocyte component was near completion. These depopulated cultured thymic fragments were then implanted into immunologically competent mouse recipients. Acute immunologic rejection was not observed in mice given cultured thymic allografts. If the organ culture period was approximately 2 weeks, lymphoid repopulation and newly developed Hassall's corpuscles were observed 7-10 weeks after implantation. If the initial culture period was extended to 3 weeks, transplanted fragments developed as unusual repopulation pattern, characterized by eosinophils, macrophages and plasma cells. This finding could be interpreted as a protracted allograft rejection or, more likely, a loss of ability of the thymic epithelium to attract or differentiate the types of precursors usually attracted to the normal gland. When cultured and non-cultured tissues were simultaneously transplanted in a single recipient, the non-cultured tissue was acutely rejected and became fibrous, while the cultured thymus assumed the appearance of a normal lymphoid organ without any neighbouring inflammatory reaction.

Transplantation of cultured thymic fragments. II. Results in nude mice.

“…No thymidine incorporation was seen. Further, in other previous studies we showed that the chemotactic influence of thymic explants diminished considerably as the culture time was lengthened (15). It was also shown that lymphoid repopulation of transplanted tissue was poor when the pieces were cultured for longer periods (15).…”

“…Samples were taken at frequent intervals for frozen section and when thymocyte and macrophage depletion was judged to be as complete as possible without notable deterioration of epithelial components, the tissues were transplanted. Previous experiments, employing transplantation into normal animals as well as chemotaxis experiments have indicated that too lengthy a culture period results in decreased chemotactic capability of the fragments and poor lymphoid repopulation in vivo (15). x The usual time of culture was 7-8 d.…”

“…In our initial studies, we utilized normal mice to show that animals with normal prethymic stem cell compartments could repopulate transplanted thymic fragments which had been depleted of lymphocytes and macrophages by a short period of organ culture (15). These studies indicated that indeed the cultured thymic fragments could become lymphoid and were morphologically normal.…”

Transplantation of Cultured Thymic Fragments: Results in Nude Mice

“…Such tissue may be less effective in attracting and/or maturing precursor T lymphocytes. The length of culture time is important; previous studies [21][22] have shown that, for mouse CTF, the lymphoid repopulation was poor and the in vitro chemotactic influence of CTF diminished with longer culture periods.…”

Transplantation of Cultured Bursal Epithelium: A Histologic Study

“…Previous work in our laboratory with thymus epithelium has shown that after 16-22 days of culture the tissue is nearly devoid of donor lymphocytes. Those few that remain are dead (10). In this study, histologic and immunofluorescent examination of the bursal epithelium after 13 days in culture revealed essential depletion of lymphocytes.…”