Suppressors of the graft vs graft reaction in tolerance to alloantigens

Immune response and suppressor cell activity of CBA (H-2k) mice made tolerant to allogeneic C57B1/6 (H-2b) heart graft were studied in graft-versus-graft reaction (GvGR). Intact CBA spleen cells inhibited response of (CBA X C57B1/6)F1 cells to antigenic stimulus (sheep red blood cells--SRBC), when injected together into lethally irradiated (CBA X C57B1/6)F1 mice. Spleen cells of tolerant mice were unable to decrease immune response of (CBA X C57B1/6F1 lymphocytes to SRBC and suppressed specifically the inhibition induced by intact CBA spleen cells. Spleen cells from tolerant mice were also capable of suppressing GvGR induced by CBA lymphocytes immune to C57B1/6 cells. Pretreatment of tolerant spleen cells with rabbit antithymocyte globulin and complement before adoptive transfer diminished markedly the suppression. The results obtained in the study suggest that suppression of transplantation immunity in this model is mostly due to T suppressor cells.     

Degradable rosin-ester-caprolactone graft copolymers

We have carried out the synthesis of side-chain rosin-ester-structured poly(ε-caprolactone) (PCL) through a combination of ring-opening polymerization and click chemistry. Rosin structures are shown to be effectively incorporated into each repeat unit of caprolactone. This simple and versatile methodology does not require sophisticated purification of raw renewable biomass from nature. The rosin properties have been successfully imparted to the PCL polymers. The bulky hydrophenanthrene group of rosin increases the glass-transition temperature of PCL by >100 °C, whereas the hydrocarbon nature of rosin structures provides PCL excellent hydrophobicity with contact angle very similar to polystyrene and very low water uptake. The rosin-containing PCL graft copolymers exhibit full degradability and good biocompatibility. This study illustrates a general strategy to prepare a new class of renewable hydrocarbon-rich degradable biopolymers.     

Studies on graft unions

Summary De novo formation of cytoplasmic cell connections are studied at the graft interface of 5 day old in vitro heterografts ofVicia faba onHelianthus annuus. Continuous and half plasmodesmata, both branched and unbranched, are described at various stages of development in non-division walls between unlike and like dedifferentiated callus cells. In apical portions of protruding callus cells and in the contact zone between opposing cells extremely thin wall parts with a striking ER/plasmalemma contact are observed. During subsequent thickening of the modified wall parts cytoplasmic strands enclosing constricted ER cisternae are entrapped within the newly deposited wall material. These cytoplasmic strands represent half plasmodesmata which—in case of fusion with corresponding structures of adjoining cells across the loosened wall matrix — form continuous cell connections. Golgi vesicles secreting wall material are involved in the process of forming half and continuous plasmodesmata, thus following the same mechanism of plasmodesmata development as described for isolated protoplasts in cell cultures. The findings suggest the existence of a unifying mechanism of secondary formation of plasmodesmata showing far-reaching similarities with the establishment of primary cell connections.     

Studies on graft unions

Summary The occurrence of plasmodesmata in the graft interfaces of two heteroplastic grafts (Impatiens walleriana onImpatiens olivieri andHelianthus annum onVicia faba) has been studied. For both systems two types of intercellular strand are described: 1. Continuous plasmodesmata interconnecting the cells of stock and scion and 2. half plasmodesmata traversing the wall part of one partner cell without connection to the abutting cell. Single strands or branched forms occur in both types of plasmodesma. In the case of half plasmodesmata, branchings with extended median nodules predominate. The distribution of half and continuous plasmodesmata varies with the different areas of a graft interface: in the region of bridging vascular tissues most cell connections are continuous. In areas where cortex or pith-derived callus cells and those of misaligned tissues (cortex/vascular tissue; cortex/pith; pith/vascular tissue) match, discontinuous strands predominate.Branched half plasmodesmata also occur in presumably fused walls between related callus cells; they are typical structures secondarily formed in non-division walls.The results are discussed with regard to compatibility/incompatibility phenomena in heterografts and the development and function of interspecific cell bridges.     

Tissue graft rejection in mice

A tissue slice-to-kidney bed grafting system is used to study the mechanism of specific tissue rejection (in this case, rejection of liver tissue) over a series of histocompatibility barriers other than the H-2 barrier. Using the method described, it is possible to obtain a pattern or time-course picture of the immunological process, rather than a mean survival time. It is clear from histological observations of these patterns that, although there are considerable differences in numbers of liver grafts which survive for long period's across the several histocompatibility barriers studied, some grafts in almost every case survive the immunological challenge elicited by the genetic barriers. Grafts of liver tissue are therefore similar, but not identical, in survival patterns to grafts of tumor, ovary, and skin. These studies also indicate that immunological mechanisms controlling rejection of tissue over H barriers other than H-2 differ from those controlling rejection over the major histocompatibility barrier in the mouse.     

Tissue graft rejection in mice

A liver-slice to kidney-bed grafting system was used to study the course of rejection of a specific tissue across various genetic barriers in inbred strains of mice. Rejection or survival, scored histologically at various times after grafting, demonstrated that multiple nonH-2 differences cause rejection at least as rapidly asH-2 differences. Differences at theK end of the mouse major histocompatibility complex cause tissue rejection more rapidly than do differences at theD end of the complex. The latter differences cause chronic rejection similar to that found across several minorH locus barriers. TheH-2 haplotype carried by the recipient or the strength of theH-2 antigens of the donor affect the survival time in liver tissue grafts. Studies employing this model system will contribute to the definition of different immunogenetic parameters affecting survival of various tissues in a genetically well-defined animal model.     

The epidermis as a graft

Laboratory epidermal autotransplantation was performed on the surface of a full-thickness skin defect using mongrel female rats. Epidermal graft represented suction blister roofs, formed as the result of the donor skin site treatment with lowered up to -0.6 kg/cm2 pressure. It contained all epidermal cell layers. Following 1, 7 and 28 days after the transplantation recipient bed sites containing grafted epidermis were excised and histological study war performed. It was demonstrated that epidermal graft received by the method described was able to grow as well as to differentiate on the surface of a full-thickness skin defect.     

Free vascularized thin corticoperiosteal graft

This paper describes a new thin corticoperiosteal graft harvested from the medial condylar and supracondylar areas of the femur. It is based on the articular branch of the descending genicular artery and vein and consists of periosteum with a thin (0.5 to 1.0 mm) layer of outer cortical bone. By retaining the cortex, the cambium layer is preserved, and this is thought to have a better osteogenic capacity than vascularized periosteal grafts. This graft was used to treat six patients with fracture nonunion of the upper extremity in which conventional treatment had failed. Uneventful bony union was achieved in all patients within 10 weeks.