C-kit-derived CD11b+ cells are critical for cardiac allograft prolongation by autologous C-kit+ progenitor cells.

Autologous C-kit+ cells robustly prolong cardiac allografts. As C-kit+ cells can transdifferentiate to hematopoietic cells as well as non-hematopoietic cells, we aimed to clarify the class(es) of C-kit-derived cell(s) required for cardiac allograft prolongation. Autologous C-kit+ cells were administered post-cardiac transplantation and allografts were evaluated for C-kit+ inoculum-derived cells. Results suggested that alloimmunity was a major signal for trafficking of C-kit-derived cells to the allograft and demonstrated that C-kit+ inoculum-derived cells expressed CD11b early after transfer. Allograft survival studies with CD11b-DTR C-kit+ cells demonstrated a requirement for C-kit+-derived CD11b+ cells. Co-therapy studies demonstrated near complete abrogation of acute rejection with concomitant CTLA4-Ig therapy and no loss of prolongation in combination with Cyclosporine A. These results strongly implicate a C-kit-derived myeloid population as critical for allograft preservation and demonstrate the potential therapeutic application of autologous C-kit+ progenitor cells as calcineurin inhibitor-sparing agents and possibly as co-therapeutics for durable graft survival.

Disruption of Transplant Tolerance by an "Incognito" Form of CD8 T Cell-Dependent Memory.

Several approaches successfully achieve allograft tolerance in preclinical models but are challenging to translate into clinical practice. Many clinically relevant factors can attenuate allograft tolerance induction, including intrinsic genetic resistance, peritransplant infection, inflammation, and preexisting antidonor immunity. The prevailing view for immune memory as a tolerance barrier is that the host harbors memory cells that spontaneously cross-react to donor MHC antigens. Such preexisting "heterologous" memory cells have direct reactivity to donor cells and resist most tolerance regimens. In this study, we developed a model system to determine if an alternative form of immune memory could also block tolerance. We posited that host memory T cells could potentially respond to donor-derived non-MHC antigens, such as latent viral antigens or autoantigens, to which the host is immune. Results show that immunity to a model nonself antigen, ovalbumin (OVA), can dramatically disrupt tolerance despite undetectable initial reactivity to donor MHC antigens. Importantly, this blockade of tolerance was CD8+ T cell-dependent and required linked antigen presentation of alloantigens with the test OVA antigen. As such, this pathway represents an unapparent, or "incognito," form of immunity that is sufficient to prevent tolerance and that can be an unforeseen additional immune barrier to clinical transplant tolerance.

Interferon Gamma and Contact-dependent Cytotoxicity Are Each Rate Limiting for Natural Killer Cell-Mediated Antibody-dependent Chronic Rejection.

Natural killer (NK) cells are key components of the innate immune system. In murine cardiac transplant models, donor-specific antibodies (DSA), in concert with NK cells, are sufficient to inflict chronic allograft vasculopathy independently of T and B cells. In this study, we aimed to determine the effector mechanism(s) required by NK cells to trigger chronic allograft vasculopathy during antibody-mediated rejection. Specifically, we tested the relative contribution of the proinflammatory cytokine interferon gamma (IFN-γ) versus the contact-dependent cytotoxic mediators of perforin and the CD95/CD95L (Fas/Fas ligand [FasL]) pathway for triggering these lesions. C3H/HeJ cardiac allografts were transplanted into immune-deficient C57BL/6 rag-/- γc-/- recipients, who also received monoclonal anti-major histocompatibility complex (MHC) class I DSA. The combination of DSA and wild-type NK cell transfer triggered aggressive chronic allograft vasculopathy. However, transfer of IFN-γ-deficient NK cells or host IFN-γ neutralization led to amelioration of these lesions. Use of either perforin-deficient NK cells or CD95 (Fas)-deficient donors alone did not alter development of vasculopathy, but simultaneous disruption of NK cell-derived perforin and allograft Fas expression resulted in prevention of these abnormalities. Therefore, both NK cell IFN-γ production and contact-dependent cytotoxic activity are rate-limiting effector pathways that contribute to this form of antibody-induced chronic allograft vasculopathy.

Prolongation of cardiac allograft survival by a novel population of autologous CD117+ bone marrow-derived progenitor cells.

Autologous CD117(+) progenitor cells (PC) have been successfully utilized in myocardial infarction and ischemic injury, potentially through the replacement/repair of damaged vascular endothelium. To date, such cells have not been used to enhance solid organ transplant outcome. In this study, we determined whether autologous bone marrow-derived CD117(+) PC could benefit cardiac allograft survival, possibly by replacing donor vascular cells. Autologous, positively selected CD117(+) PC were administered posttransplantation and allografts were assessed for acute rejection. Although significant generation of recipient vascular cell chimerism was not observed, transferred PC disseminated both to the allograft and to peripheral lymphoid tissues and facilitated a significant, dose-dependent prolongation of allograft survival. While CD117(+) PC dramatically inhibited alloreactive T cell proliferation in vitro, this property did not differ from nonprotective CD117(-) bone marrow populations. In vivo, CD117(+) PC did not significantly inhibit T cell alloreactivity or increase peripheral regulatory T cell numbers. Thus, rather than inhibiting adaptive immunity to the allograft, CD117(+) PC may play a cytoprotective role in prolonging graft survival. Importantly, autologous CD117(+) PC appear to be distinct from bone marrow-derived mesenchymal stem cells (MSC) previously used to prolong allograft survival. As such, autologous CD117(+) PC represent a novel cellular therapy for promoting allograft survival.

The suspensory ligament of the clitoris: connective tissue supports of the erectile tissues of the female urogenital region.

We aimed to define the gross anatomy of the supporting structures of the clitoris. We performed a dissection of the perineum of a series of 22 female and four male cadavers. Specific dissection of the clitoral and penile suspensory ligament complex was performed in four female and two male cadavers. Serial written observations and photography were used to document the findings. Our findings were then compared with the anatomical description of these structures in the historical and current anatomical literature. The suspensory ligament of clitoris consistently displayed two components: a superficial fibro-fatty structure extending from a broad base within the mons pubis to converge on the body of the clitoris and extending into the labia majora: in addition there is a deep component with a narrow origin on the symphysis pubis extending to the body and the bulbs of the clitoris. The supporting structures of the clitoris are more substantial and complex than previously described. Their shape, extent, and orientation are different from analogous structures of the penis, the suspensory ligament of which was found as described in the literature.

Anatomical relationship between urethra and clitoris.

PURPOSE: We investigated the anatomical relationship between the urethra and the surrounding erectile tissue, and reviewed the appropriateness of the current nomenclature used to describe this anatomy. MATERIALS AND METHODS: A detailed dissection was performed on 2 fresh and 8 fixed human female adult cadavers (age range 22 to 88 years). The relationship of the urethra to the surrounding erectile tissue was ascertained in each specimen, and the erectile tissue arrangement was determined and compared to standard anatomical descriptions. Nerves supplying the erectile tissue were carefully preserved and their relationship to the soft tissues and bony pelvis was noted. RESULTS: The female urethra, distal vaginal wall and erectile tissue are packed into the perineum caudal (superficial) to the pubic arch, which is bounded laterally by the ischiopubic rami, and superficially by the labia minora and majora. This complex is not flat against the rami as is commonly depicted but projects from the bony landmarks for 3 to 6 cm. The perineal urethra is embedded in the anterior vaginal wall and is surrounded by erectile tissue in all directions except posteriorly where it relates to the vaginal wall. The bulbs of the vestibule are inappropriately named as they directly relate to the other clitoral components and the urethra. Their association with the vestibule is inconsistent and, thus, we recommend that these structures be renamed the bulbs of the clitoris. CONCLUSIONS: A series of detailed dissections suggest that current anatomical descriptions of female human urethral and genital anatomy are inaccurate.